Ternary phases forming adjacent to Al3MnAl4Mn in AlMnTM (TM = Fe, Co, Ni, Cu, Zn, Pd)

Journal of Alloys and Compounds 677 (2016) 148e162

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Ternary phases forming adjacent to Al3MneAl4Mn in AleMneTM (TM ¼ Fe, Co, Ni, Cu, Zn, Pd) B. Grushko a, b, *, D. Pavlyuchkov c, d, S.B. Mi e, S. Balanetskyy c a

MaTecK, D-52428 Jülich, Germany PGI-5, Forschungszentrum Jülich, D-52425 Jülich, Germany c Department of Physical Chemistry of Inorganic Materials, I.N. Frantsevich Institute for Problems of Materials Science, 03680 Kyiv 142, Ukraine d Institute of Materials Science, Technical University of Freiberg, D-09599 Freiberg, Germany e State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, PR China b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 4 February 2016 Accepted 25 March 2016 Available online 29 March 2016

The AleMn alloy system contains complex intermetallics in its Al-rich part, and this was the first system where quasiperiodic structures were recognized. In the present work, the solubility of TMs (TM ¼ Fe, Co, Ni, Cu, Zn and Pd) in the stable binaries, the stabilization effect of these elements on the metastable binaries and the formation of ternary compounds are specified and compared. While the solubility of all these TMs in hexagonal m-Al4Mn and l-Al4Mn is low, the high-temperature orthorhombic T-Al3Mn dissolves up to at least 14.5, 12, 16 and 7.5 at.% Fe, Cu, Zn and Pd, respectively. The metastable hexagonal 4-Al10Mn3 is stabilized by Fe, Co and Ni in wide ternary compositional regions, and in AleCoeMn such a region propagates up to Al5Co2. In alloys with Fe, Co and Ni, a ternary hexagonal phase isostructural to the AleCreNi z-phase (P63/m, a z 1.76, c z 1.25 nm) is formed along ~80 at.% Al, while in alloys with Cu and Pd the orthorhombic so-called R-phase (Bbmm, a z 2.41, b z 1.25, c z 0.76 nm) was found at similar compositions. This structure is also known in AleZneMn but at much lower-Al Al68Zn14.5Mn17.5, while in the range of 75e80 at.% Al a monoclinic phase isostructural to h-Al11Cr2 (C2/c, a z 1.76, b z 3.04, c z 1.76 nm, b z 90 ) is formed. In addition to the stable decagonal D3-phase in AleFeeMn and AlePdeMn reported earlier, the stabilization of binary AleMn D3-phase was revealed around Al64Cu20Mn16. © 2016 Elsevier B.V. All rights reserved.

Keywords: Transition metal alloys and compounds Phase diagrams

1. Introduction Investigations of binary and ternary aluminum alloys with manganese and other transition elements have been in progress since the beginning of the 20th century. Particularly, the binary AleMn phase diagram has been significantly revised several times. Its Al-rich part contains several complex intermetallic phases, and the formation of quasiperiodic icosahedral and decagonal structures was reported for the first time in this alloy system. First experiments with ternary alloys based on AleMn started long before there was good knowledge of the boundary binary phase diagrams. This primarily concerned the systems containing the elements adjacent to Mn in the periodic table such as Cr, Fe, Co, Ni, Cu and Zn.

* Corresponding author. PGI-5, Forschungszentrum Jülich, D-52425 Jülich, Germany. E-mail address: [email protected] (B. Grushko). http://dx.doi.org/10.1016/j.jallcom.2016.03.220 0925-8388/© 2016 Elsevier B.V. All rights reserved.

Even at the moment the information on these systems is controversial. For the following description the relevant part of the AleMn phase diagram in the presently accepted form is shown in Fig. 1 [1] and the crystallographic data of the relevant phases are provided in Table 1. It should be noted that the presence of two phases close to the Al3Mn composition, forming at higher and lower temperatures, was established only in 1960 [2], while the metastable so-called 4-Al10Mn3 phase was still recognized at that time as stable. The present configuration of this compositional region was specified only in 1971 [3].1 The presently accepted positioning of the m-Al4Mn and l-Al4Mn was argued in 1987 [4], i.e. after the discovery of the

1 In the literature the high-temperature phase designated Al3Mn [2] or h-Al11Mn4 [3] is frequently named Taylor's phase (T-phase). On the other hand, in several publications cited below, T was used to designate any ternary phase. In order to avoid confusion, the symbols of these ternary phases are supplied by subscripts indicating the third element, for example, TCu for a ternary phase in AleCueMn.

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162

1200

Temperature, °C

1048

δ

L

1000

γ1

1002

T

923 910

957 895

984

γ2

ν

800 705

μ

Al6Mn

658

(Al)

600 0

695

λ

10

20 Mn, at % 30

40

Fig. 1. Partial AleMn phase diagram [1]. The phases are specified in Table 1.

metastable AleMn quasicrystals close to these compositions. Since the first studies the structures of the binaries have also been under discussion. The ternary AleCueMn system attracted attention much earlier. Two complex orthorhombic structures were reported there by Petri [5] on the basis of the X-ray diffraction study of needle-shaped single crystals. The phase designated T (TCu in the following, a ¼ 0.769, b ¼ 2.406 and c ¼ 1.248 nm) was found between ~Al80.1Cu7.8Mn12.1 and ~Al77.7Cu6.9Mn15.4, i.e. close to the binary Al4Mn phase. The other phase designated Y (a ¼ 1.479, b ¼ 1.260, c ¼ 1.243 nm) was observed in a range of compositions adjacent to

149

AleMn, particularly a composition ~Al76.9Cu3.1Mn20.0 was reported. In a study of AleCueMn alloys Raynor [6] cited Petri's findings without confirming or negating them. No ternaries were revealed in this work in AleCoeMn and AleFeeMn, which dealt only with very low concentrations of the third elements. On the other hand, the same author also reported two ternary AleNieMn phases [7]. One of them, designated X, was revealed in a small compositional region around Al60Mn11Ni4 (zAl80Ni5.3Mn14.7), i.e. its Al and Mn concentrations were close to those of Petri's TCu-phase. The composition of the other ternary AleNieMn phase, designated Y and suggested to be metastable, was not specified. No structural information on these phases was provided in Ref. [7]. In Ref. [8] three ternary phases designated T1, T2 and T3 were reported in AleZneMn (TZn1, TZn2 and TZn3 in the following). The composition of the TZn1-phase ~Al80Zn3.2Mn16.8 was found to be “equivalent” to those of Al60Mn11Ni4 or Al20Mn3Cu2 [8], considering their very close electron-to-atom ratio e/a z 1.85. In a later Ref. [9] by Robinson, the single crystals of both Al60Mn11Ni4 and Al20Mn3Cu2 were reported to be orthorhombic, structurally very similar between them and also similar to that of Petri's TCu-phase (Bbmm, a ¼ 2.38, b ¼ 1.25, c ¼ 0.755 nm, R-phase in the following), but the structure of Al80Zn3.2Mn16.8 was different. On the other hand, a great similarity to the R-phase was concluded in Ref. [10] for the TZn3-phase despite its quite different composition of Al67.4Zn15.7Mn16.9 (Al68.8Zn13.7Mn17.5 according to [8]). More recently, the structure of TZn1 was concluded to be rather similar to that of the monoclinic (b z 90 ) Al11Cr2 phase [11]. The structure of the TZn2-phase forming at intermediate composition Al9ZnMn2 (Al74.7Zn8.3Mn16.7) was not reported. A structural model of Al60Mn11Ni4 published in Ref. [12] was expected to be applicable to Al20Mn3Cu2, while for TZn3 some different cite occupancies were derived in Ref. [10] due to another ratio between the Al and TM concentrations. At that time the phase equilibria in the corresponding ternary systems were not yet established. For the following description the relevant details of the quoted ternary phase diagrams are presented in Fig. 2 according to the presently available literature data.

Table 1 Crystallographic data of the relevant phases. TW means this work. Phase

Space group

Al6Mn l-Al4Mn m-Al4Mn T-Al3Mn (h-Al11Mn4)

Cmcm P63/m P63/mmc Pnma

4

P63/mmc

z

P63/m

R

Bbmm

O

Orth. C2/c

h

Lattice parameters a, nm a, 

b, nm b, 

c, nm g, 

0.75551 2.8382 2.0015 1.4873 1.46256(6) 1.4782 1.4726 1.48447(5) 0.7543 0.76632 0.7580(1) 0.7554 1.7625 1.7562(2) 1.7536(3) 1.7530(3) 1.76058(7) 1.7630 2.41023(15) 2.4106(4) 2.3316 1.7615(1)

0.64994 e e 1.2420 1.24557(4) 1.2423 1.2514 1.25024(7) e e e e e e e e e e 1.24787(8) 1.2495(2) 1.2424 3.0362(3) 90.656(8)

0.88724 1.2389 2.4699 1.2547 1.25469(6) 1.2524 1.2605 1.26359(6) 0.7898 0.78296 0.7879(1) 0.7872 1.2516 1.2459(2) 1.2444(2) 1.2440(2) 1.24638(3) 1.2506 0.76102(7) 0.7645(1) 3.2648 1.7598(2) e

e

Ref. Comment

[1] [26] [18], Al79.8Mn20.2 [46], Al72.8Mn27.2 TW, Al70Cu11.5Mn18.5, Appen. A [21], Al73Fe2Mn25 [46], Al72.4Pd6.5Mn21.1 TW, Al66Zn16Mn18 [1], Al10Mn3 [18], Al73.1Ni7.8Mn19.1 TW, Al74.7Co3.7Mn21.6 [21], Al76.1Fe6.2Mn17.7 [18], Al80.3Ni2.2Mn17.5 TW, Al80.0Ni5.3Mn14.7 TW, Al80.0Ni2.7Cu2.7Mn14.6 TW, Al80.0Ni1.9Cu3.5Mn14.6 TW, Al80Co3.1Mn16.9, Appen. C [21], Al81.4Fe3.6Mn15.0 TW, Al80Cu8Mn12, Appen. B TW, Al80.0Ni0.9Cu4.6Mn14.5 [18], Al78.4Ni8.3Mn13.3 TW, Al74.4Zn9.0Mn16.6, Appen. D

150

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162

Al

a)

Al

d)

L

LL 10

10

90

90

Al6Mn 20

TCu

μ

20

ζ

μ

80

Y

φ

ν

ν

Al5Fe2

TCu

D3

T

10

20

10

Cu at.%

Al

b)

80 Al13Fe4

20

e)

L

Fe at.%

(Al) 10

10

90

90 Al6Mn

20

Al9Co2

TCo

μ

80

Al5Co2

ν 10

Al

20

TZn1 μ

Al13Co4

φ

λ

20

30

Co at.%

TZn3

τ3

c) 10

20

ν

10

90

ζ

20

Zn at.%

80

O

Al3Ni

φ 10

TZn3 τ1 τ4

L

μ

L

τ2

τ2

ν

80

τ1 T Zn2

20

Ni at.%

Fig. 2. Partial isothermal sections of: a) AleCueMn at 750  C [13], b) AleCoeMn at 800  C [14], c) AleNieMn at 750  C [18], d) AleFeeMn at 875  C [21], e) AleZneMn at 600  C [23]. The temperatures were selected in order to include major relevant information. L is the liquid, D3 is the decagonal phase. The z-phase is designated k in Refs. [18] and [21]. In (a) the compositions of the ternary phases TCu and Y reported in Ref. [5] are marked in black. In (e) the ternary phases t1t4 are marked by blue regions and symbols and white squares indicate the compositions of the single-phase samples. The ternary phases t1 and t2 of Ref. [24] are marked by brown regions and symbols, white squares indicate the measured compositions of the phases. The ternary phases TZn1TZn3 according to Ref. [8] are marked by black squares and symbols, TZn3 according to Ref. [10] is marked by a red square and symbol. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

The entire ternary AleCueMn phase diagram was first pub€ster and Go €decke [13], and still remains the most lished by Ko detailed description of this system. These authors accepted the TCuphase of [5] but placed it at ~10 at.% lower Al concentrations (Fig. 2a). Another ternary phase was reported to be formed at the still lower Al concentration Al57.9Cu26.3Mn15.8 and below ~700  C. Its structure was different from that of the Y-phase reported in Ref. [5], while the latter was just mentioned as not confirmed. An investigation of the ternary AleCoeMn phase diagram by the same authors [14] also revealed a ternary T-phase (TCo in the following) close to Al4Mn (Fig. 2b). Based on powder X-ray diffraction examination, it was suggested to have the same

orthorhombic structure as Al62Ni3Mn13 (zAl79.5Ni3.8Mn16.7) mentioned in Ref. [15]. However, Ref. [15] did not contain structural details and was solely devoted to the compositional refinement of the ternary phase associated with the above-mentioned Raynor's Al60Mn11Ni4. In addition to this identification, far from being direct, the so-called AleZneMn TZn3-phase of [10] was mentioned in Ref. [14] as belonging to the same structural type, but not the abovementioned AleCueMn TCu-phase reported earlier by the same authors. It seems they just avoided stating the structures of these phases and no structural data were included in either Ref. [13] or Ref. [14]. The R-phase became popular in the 1980s and 1990s due to its

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162

suggested structural relation to icosahedral and decagonal quasicrystals. In AlePdeMn, where stable quasicrystals were especially extensively studied, the R-type structure was found to coexist with the ternary extension of the AleMn T-phase, and the structural relations of these periodic phases were emphasized ([16] and references therein). Despite numerous citations of Robinson's work on Al60Mn11Ni4, only a few new experimental studies of AleNieMn alloys were published. Surprisingly, besides the observation of metastable AleNieMn quasicrystals, similar to those in AlePdeMn, other than the R-phase periodic structures were reported in the same alloy compositions, for example the orthorhombic so-called C3,I-phase (a ¼ 1.24, b ¼ 2.40, c ¼ 3.27 nm) [17]. On the other hand, in a more recent systematic study of the AleNieMn phase diagram the structure of a phase forming around the Al60Mn11Ni4 composition was concluded to be hexagonal [18,19], resembling that of the AleNieCr so-called k-phase [20]. A similar hexagonal structure was also revealed close to Al4Mn in the AleFeeMn alloy system, extensively studied in Ref. [21]. In the following this phase is designated z in order to be consistent with that used in the AleNieCr phase diagram of Ref. [22] and other publications by the present authors. The relevant region of the AleNieMn phase diagram is shown in Fig. 2c and of AleFeeMn in Fig. 2d. As to the AleZneMn phase diagram, it was recently studied at 600  C in Ref. [23] and independently at 400  C in Ref. [24]. The results of the two studies are inconsistent with each other and with the earlier findings (see Fig. 2e). In approximately the same compositional region instead of the three phases of Ref. [8] four ternary phases were reported in Ref. [23] and only two in Ref. [24]. In Ref. [23] three of the four single phases were extracted and studied by powder X-ray diffraction, but neither of the diffraction patterns was identified with Robinson's or any other known structure. In contrast, the formation of the R-phase was suggested in several multiphase samples studied in Ref. [24]. Its composition Al71Zn13Mn16 was mentioned (the so-called t2-phase), but in Table 2 of [24] the compositions of this phase ranged from 72 to 75 at.% Al (see Fig. 2e) almost reaching that of the TZn2-phase of [8]. Considering these controversies, the constitutions of the abovementioned systems and the structures of the relevant phases were re-examined.

2. Experimental The alloys were produced by levitation induction melting in a water-cooled copper crucible under a pure Ar atmosphere. The ingot weights were typically ~5 g. Alloys containing Zn were produced by melting Al with Mn and then by remelting the binary alloys with Zn taken in extra quantities. Due to strong evaporation of Zn, its loss was examined and, if needed, compensated by the addition of Zn in subsequent annealing performed in closed quartz ampules. The samples were protected from contact with the quartz by alumina crucibles. Parts of the ingots were thermally annealed at the temperatures and for the times specified in the corresponding sections. The alloys were examined by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The local phase compositions were determined in SEM by energy-dispersive X-ray analysis (EDX) on polished unetched cross-sections. Powder XRD was carried out in the transmission mode using Cu Ka1 radiation and an image plate detector. Analyses of the powder XRD patterns were carried out using the MAUD program [25]. Selected samples were studied in the transmission electron microscope (TEM) on powdered materials dispersed on Cu grids with an amorphous carbon film.

151

3. Results and discussion 3.1. AleMn The relevant part of the AleMn phase diagram is accepted from Ref. [1]. It contains the equilibrium phases Al6Mn, l-Al4Mn, mAl4Mn, the low-temperature l-Al11Mn4 (n-phase) and the hightemperature T-phase. The latter designation is more reasonable than Al3Mn or h-Al11Mn4 due to its existence in a wide binary compositional region and wide extensions in many ternary alloy systems. The structural models of the AleMn l-phase [26], m-phase [27] and T-phase [28] were accepted for their identification in experimental powder XRD patterns. Kinetic effects during phase transitions of the AleMn alloys emphasized in Refs. [4,29e31] complicated the determination of the genuine equilibrium. Metastable phases can be formed in AleMn by rapid or even ordinary solidification [4]. Thus, the hexagonal phase 4-Al10Mn3 (see Table 1) was earlier suggested to be stable, but was removed from the phase diagram in later versions. Indeed, its estimated Gibbs energy is close to that of the T-phase, which is only stable at elevated temperatures [4]. By the addition of a third element the mutual stability of these phases can reverse, as was observed in experiments (see below). Also the peritectic formation of the l-phase at 721  C was claimed recently in Refs. [29,31], while the experimental results in Ref. [30] were rather consistent with the previous diagram of Ref. [4]. The metastable decagonal quasicrystalline D3-phase2 can be produced by ordinary solidification, while the formation of the metastable icosahedral I-phase required rapid solidification. In solidified alloys the D3-phase was frequently observed together with the T-phase and exhibited very close compositions. An orthorhombic p-phase with an approximate composition of A14Mn was also found to coexist with the decagonal quasicrystals in rapidly solidified alloys [32]. The diffraction patterns and lattice parameters of the p-phase were very similar to those of the abovementioned R-phase. 3.2. AleCueMn According to Ref. [13], the AleCueMn alloy system adjacent to Al3MneAl4Mn includes a ternary TCu-phase, whose structure was associated with that of the R-phase of [9,12]. In the 700  C isothermal section of [13] it was shown around ~Al70Cu11.5Mn18.5 in contrast to the compositional region of such a phase mentioned in Ref. [5] (Fig. 2a), and at higher temperatures its Al concentration was even lower. The reaction L þ Al8Mn5 4 TCu was concluded at 1020  C. Negligible solubility of Cu was reported in Al6Mn, Al4Mn and Al11Mn4, while the region close to AleCu was obviously occupied by the liquid. In our experiments a sample of Al70Cu11.5Mn18.5 annealed at any temperature in the range of 550e850  C consisted of an essentially single phase different from the expected R-phase. The corresponding powder XRD pattern (Fig. 3a, the annealing conditions are given in the figure caption) was successfully indexed for another orthorhombic phase (see Appendix A and Table 1). Its structure resembled the description of Petri's Y-phase [5], which in Ref. [13] was reported as not being confirmed. Moreover, its diffraction data were also very similar to those of the AleMn T-phase (see Table 1), already known at the time of the publication of Ref. [13]. The diffraction pattern of the T-phase calculated from the structural model of Ref. [28] illustrates the correctness of the identification

2 It is designated D3 according to the systematics, where the decagonal phases with periodicities of ~4n nm in the specific direction are designated Dn.

152

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Fig. 3. Powder XRD patterns (Cu Ka1-rad.) of: a) the T-phase in Al70Cu11.5Mn18.5 annealed at 750  C for 332 h, b) the T-phase calculated using the data of Ref. [28], c) the R-phase coexisting with the liquid in Al80Cu8Mn12 annealed at 700  C for 230 h (the Al line corresponds to the solidified liquid), d) the R-phase calculated using the data of Ref. [12], e) mAl4Mn, powdered single crystal, f) the D3-phase of Al64Cu20Mn16 annealed at 750  C for 238 h, g) the z-phase in Al80Ni5.3Mn14.7 annealed at 750  C for 161 h, h) the z-phase calculated using the data of Ref. [20].

(Fig. 3b). Therefore, the ternary TCu-phase of [13] is actually the ternary extension of the AleMn T-phase, as was even suggested in Ref. [5]. This also explains such a huge compositional deviation of the TCu-phase in Ref. [13] from that in Ref. [5] mentioned above. The “real” TCu-phase was simply overlooked in Ref. [13] but was reported in numerous publications on commercial Al alloys ([33] and references therein) under the designation Al20Cu2Mn3 given to it in Ref. [9]. Indeed, a sample of Al80Cu8Mn12 annealed at 700  C contained this phase apart from some solidified liquid, while that of Al80Cu5.5Mn14.5 contained in addition a small quantity of a second solid phase (m-phase, see Fig. 4, the measured compositions of the phases are given in the caption). The powder XRD pattern of the major phase (see Fig. 3c) was indexed using the orthorhombic unit cell with the lattice parameters similar to those of Petri's TCu-phase (see Appendix B), which is also identical to the R-phase of Ref. [12]. The latter designation will also be used in the following in AleCueMn. The crystal structure of the R-phase described in Ref. [12] is completely applicable for the AleCueMn R-phase. Due to the neighboring positions of Ni and Cu in the periodic table also their atomic weights and X-ray scattering powers are close and their atomic radii are only 3% different. The powder XRD pattern of the Rphase calculated from the data of [12] is shown in Fig. 3d for comparison (Cu atoms were placed in Ni positions). The complex powder XRD patterns of R and T (and also of m presented in Fig. 3e) should be carefully indexed in order to avoid their erroneous identification, as probably happened in Ref. [13]. The provisional compositional regions of the T-phase and Rphase at 700  C are shown in Fig. 5a. At this temperature the Tphase is already unstable in binary AleMn and its ternary region, extending up to at least 12 at.% Cu, is disconnected from the binary terminal. The coexistence of R and T was not observed by SEM/EDX due to probably small compositional differences and also due to their formation in the form of fine weakly connected needles. Their coexistence is also difficult to observe by powder XRD due to complex diffraction patterns with numerous overlaps (see Fig. 3). On the other hand, the coexistence of R and m was mentioned above

as being observed by SEM/EDX despite their quite close compositions (Fig. 4b). Examinations of alloys with somewhat lower Al concentrations revealed another stable ternary phase around ~Al64Cu20Mn16, which is quite far from the compositions of both the ternaries reported in Ref. [13]. Its powder XRD pattern, very different from that of the T-phase, is presented in Fig. 3f. The electron diffraction examinations (see Fig. 6) revealed patterns similar to those of the metastable AleMn decagonal D3-phase (i.e. with the periodicity of ~1.2 nm in the specific direction) [34]. Such a structure, earlier observed in solidified samples at the same composition, was concluded to be metastable (see Ref. [35] and references therein), since in the reported experiments it transformed by subsequent heating up to 650  C. In our experiments the decagonal phase was found in samples annealed at 750  C for 238 h, i.e. above the temperatures applied in Ref. [35] and quite close to the solidus of this phase. More detailed investigation of the AleCueMn phase diagram is in progress. 3.3. AleNieMn Systematic investigation of the Al-rich part of the AleNieMn phase diagram [18,19] revealed stable ternary phases designated 4, O and z (k in Refs. [18,19], see Table 1) and metastable D3, but no structure corresponding to that of the R-phase of [9,12] was observed. The representative isothermal 750  C section of AleNieMn is shown in Fig. 2c. The ternary 4-phase is the abovementioned metastable AleMn 4-Al10Mn3 stabilized by Ni. It occupied a wide ternary compositional region leaving very little space for the ternary extension of the AleMn T-phase. The latter, existing at 850  C but not at 750  C, was found to extend up to ~3 at.% Ni. The complex orthorhombic structure designated C3,I in Refs. [17,36] as a major constituent forming in the Al60Mn11Ni4 alloy (Al80Ni5.3Mn14.7), was associated in Ref. [19] with a stable O-phase forming around the Al78.5Ni8.5Mn13.0 composition. On the other hand, the equilibrium structure of the phase forming at such frequently mentioned Al60Mn11Ni4 was concluded in Ref. [19] to be

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162

153

Al

a) 10 90 Al6Mn 20

μ

80 R

30

ν

L

T

70

D3 10

20

Cu at.%

(Al)

b) 10

90 Al6Mn 20

Fig. 4. SEM micrographs (backscattered electrons) of AleCueMn alloys annealed at 700  C for 230 h: a) Al80Cu8Mn12, b) Al80Cu5.5Mn14.5. The measured compositions of the R-phase (light gray) are Al77.7Cu7.0Mn15.3 and Al79.3Cu5.5Mn15.2, respectively. The measured composition of the minor m-phase (dark gray, marked by arrows) is Al80.3Cu2.3Mn17.4. Black is the solidified liquid.

hexagonal (z-phase) and not orthorhombic. The powder XRD pattern of this phase is presented in Fig. 3g. Its identification was supported by the calculations (Fig. 3h) using the structural model of the AleNieCr z-phase of Ref. [20], where Mn was placed at the positions of the Cr atoms. The indexed peak list of the z-phase was provided in Ref. [19]. It should be stressed that the phases in Ref. [19] were also identified using electron diffraction of the corresponding single-phase particles. Neither the R-phase nor the z-phase was reported in Ref. [17] to be observed in Al60Mn11Ni4. In Ref. [36], devoted to the structural model of C3,I, also the TEM observation of the R-phase was claimed in the same slowly solidified alloy. However, this was not supported by a demonstration of the diffraction patterns of R, while the highresolution (HRTEM) images of the real space presented there rather confirm its absence. In order to interpret these images let us first recall the constitution of this alloy at much lower magnification. As is shown in Fig. 8a of Ref. [18], the as-cast alloy of this composition contained the primary solidified brighter grains of ~Al75.1Mn19.2Ni5.7 surrounded by darker grains solidified at lower

μ

R

80

T I

30

70

D3

γ1 10

ε

20

Pd at.%

Fig. 5. Partial isothermal section of AleCueMn at 700  C estimated from the present results (a), and the compositional regions of the AlePdeMn phases in the solidus surface projection according to Ref. [46] (b). In (a) the compositions of the studied samples are marked by solid squares, the measured compositions of the phases are marked by open squares, provisional lines are broken, L is the liquid and D3 is the decagonal phase, whose composition is somewhat below the presented region (marked by a red arrow). In (b) I is the icosahedral phase and D3 is the decagonal phase. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

temperatures, whose compositions ranged from Al80.8Mn13.9Ni5.3 to Al80.3Mn13.3Ni6.4. By electron diffraction the former were associated with the 4-phase and the latter with a fine mixture of the partially distorted decagonal (D3) and orthorhombic (O ¼ C3,I) phases of undistinguished compositions. The electron diffraction patterns in Fig. 9 of [18] demonstrated both phases of better or worse structural perfection observed in very small parts of the same dark grains. The HRTEM image in Fig. 3a of [36] was taken from a similar

154

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Fig. 6. Principal electron diffraction patterns of the stable decagonal D3-phase in Al64Cu20Mn16 annealed at 750  C for 238 h. Reflections marked by arrows correspond to the periodicity of ~2 nm.

but even smaller zone (~15  15 nm) which exhibited a single orientation of the obviously distorted O-phase. Indeed, the tiling of the image showed its irregularity over such a very small area. In the part of the image the tiling designated h is typical of the R-phase, i.e. it consists of the elongated hexagons arranged in parallel (see Refs. [16,18] for a more detailed description), but it is too small to produce an electron micro-diffraction pattern of R, and definitely it cannot be detected by a single-crystal X-ray diffraction applied in Ref. [12]. In other parts of the HRTEM image such hexagons were arranged in a herringbone manner typical of the T-phase, which also does not mean its formation at this composition in the thermodynamically stable form. The same hexagons were assumed in Ref. [36] to be structural elements of their C3,I orthorhombic phase together with other features revealed there. Altogether, also the local R-like arrangement, visible in Fig. 3a of [36], would result in the electron diffraction patterns typical of the distorted O-phase (for example, the above-mentioned Fig. 9 of [18]). The results of a search for a stable AleNieMn decagonal phase were negative. 3.4. AleCueNieMn The phases forming at Al60Mn11Ni4 and Al20Mn3Cu2 have different crystal symmetries, which excludes the continuity of the compositional region between them in quaternary AleCueNieMn. However, such continuity was reported by Raynor and Faulkner [37] to be observed experimentally. These authors examined alloys by optical metallography after color etching. Since ternary TNi, expected to be the R-phase, was etched uniformly dark brown, while ternary TCu was uniformly light brown, they could be reliably discriminated by color. Eight alloys of quaternary compositions, lying on the straight line between Al-(2Mn, 5Ni, in wt%) and Al(2Mn, 18Cu, in wt%), were slowly cooled from the liquid. In all of them the primary crystallization consisted of homogeneous crystals of a single quaternary TNiCu phase, which was concluded by the color of the precipitates imbedded in the (Al) matrix. These tones became progressively lighter as the copper content of the alloy increased. Together with the recognition of only one type of the primary crystals this indicated the continuity of the solid solutions between TCu and TNi in the quaternary system. Based on Ref. [9], where both ternaries were concluded to be isostructural, this result was accepted as reasonable indeed, and the precipitates were not extracted from the (Al) matrix for chemical or structural examinations. However, the observations in Ref. [37] could also mean a large solubility of the fourth element in the ternaries, which could reduce the compositional discontinuity below the resolution of the

Fig. 7. Powder XRD patterns (Cu Ka1-rad.) of: a) the z-phase in Al80Ni2.7Cu2.7Mn14.6 annealed at 700  C for 230 h, b) the z-phase in Al80Ni1.9Cu3.5Mn14.6 annealed at 700  C for 230 h, c) the R-phase in Al80Ni0.9Cu4.6Mn14.5 annealed at 700  C for 168 h, and d) the z-phase in Al80Co3.1Mn16.9 annealed at 740  C for 67 h.

applied method. The solubility limits of the coexisting phases could even be between the compositions of the precipitates in the samples of neighboring compositions. Thus, as mentioned above, in AleCueMn the coexistence of R and T was not observed by SEM/ EDX. In order to clarify the solubility of the fourth element in the ternaries, a series of quaternary AleNieCueMn samples were produced by mixing the Al80Cu5.5Mn14.5 and Al80Ni5.3Mn14.7 alloys in ~1:2, 1:1 and 2:1 proportions. The as-cast alloys were subsequently annealed at 700  C. Apart from minor (Al) all of them contained only the z-phase extending from AleNieMn up to ~3.5 at.% Cu (Fig. 7a and b, compare to Fig. 3g). The corresponding lattice parameters are provided in Table 1. On the other hand, an additional sample containing ~4.6 at.% Cu annealed at 700  C contained the R-phase (Fig. 7c, compare to Fig. 3d). Therefore, the compositional discontinuity between the z-phase and the R-phase

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is quite small indeed, somewhere between 3.5 and 4.6 at.% Cu. This indicated a large solubility of Cu in the z-phase, and possibly its stabilization vs. the R-phase by only a small Ni addition, while for ~14.5 at.% Mn the maximal solubility of Ni in the R-phase is ~1 at.%. It is worth noting that in AleCueCr the z-phase and not the Rphase is formed adjacent to Al4Cr [38] similarly to that in AleNieCr [39]. In contrast to [37], the study in Refs. [9,12] was performed by X-ray diffraction on single-crystal samples, which makes it impossible to conclude a hexagonal symmetry instead of an orthorhombic. It is most plausible to suggest that actually the crystals from AleCueMn were adopted for AleNieMn. Indeed, the crystals examined by Robinson [9] were not produced by the author but were supplied by Raynor, and both Al60Mn11Ni4 and Al20Mn3Cu2 were in the delivery. In Ref. [9] no chemical analyses were carried out.3 The samples were described as crystallizing in the form of thin rectangular plates with the a-axis normal to the rectangular plate and the b-axis coinciding with the shorter of the plate ages (for the selection of the axes mentioned in our Introduction). In the crystals mentioned as Ni-containing, the b-axis coincided with the shorter of the plate edges, while in those mentioned as Cu-containing, the b-axis coincided with the longest of the plate edges and they were twinned. On the other hand, in Ref. [15] the crystals of the concluded composition Al62Ni3Mn13 were described as elongated sticks with hexagonal cross sections (Fig. 2 of [15]). The description in Ref. [5] is less definite: the c-axes (b-axis according to the settings in Ref. [9]) of both TCu and Y were selected there along the needle axes whose cross-section shapes were not specified. The unit cell dimensions and intensities of the comparable reflections of the crystals reported in Ref. [9] to contain either Ni or Cu were very close, which would also be the case if both were taken from AleCueMn ingots of different compositions. As found in Ref. [5] and confirmed in the present work, the R-phase in this alloy system is formed indeed in quite a wide compositional region. 3.5. AleCoeMn The AleCoeMn phase diagram was constructed in Ref. [14] and to date remains the most detailed description of this system. The representative Al-rich part of its isothermal 800  C section is shown in Fig. 2b. This study revealed low solubility of Co in Al6Mn, Al4Mn and Al11Mn4 but very elongated ternary extensions of Al13Co4 and Al5Co2. The latter almost propagates up to the AleMn terminal. The unique ternary phase was reported in Ref. [14] close to Al4Mn. It was found to be formed by a peritectic reaction at 895  C at Al79.4Co2.0Mn18.6 and extended at lower temperatures in a small compositional region towards higher Co concentrations. In order to clarify the structure of this ternary phase, a sample of Al80Co3.1Mn16.9 selected according to the data of [14] and annealed at 740  C for 67 h consisted of an essentially single phase. The powder X-ray examination of the latter revealed a great similarity of its diffraction pattern (Fig. 7d) to that of the above-mentioned AleNieMn z-phase, which allowed us to associate TCo of [14] with the z-phase structure. Its diffraction data are provided in Appendix C. Since the publication of Ref. [14], the refinement of AleMn revealed the l-Al4Mn phase, while in AleCo several structural variants of Al13Co4 were reported [41]. According to our

3 The samples were probably those extracted during the study reported in Refs. [6,7], and soon after that Raynor moved from Oxford to Birmingham [40]. Due to move and the passage of several years before the delivery of the samples to Robinson, their identification could be questionable.

155

examinations these updates did not significantly influence the constitution of the ternary region. The constitutions of several alloys in the relevant compositional region investigated at 740e910  C were qualitatively consistent with the equilibria reported in Ref. [14] (see Fig. 8), which allowed us to use the corresponding phase diagram for the further discussion. The z-phase, produced in the above-mentioned Al80Co3.1Mn16.9 at 740  C, transformed by heating at 910  C (i.e. above the melting temperature of the z-phase reported in Ref. [14]), and the alloy contained the major hexagonal phase of the Al5Co2type structure and the liquid. In the following this phase is designated 4 similarly to that in AleNieMn. Its diffraction pattern in Fig. 9a is taken from the single-phase sample of Al74.3Co3.6Mn22.1 annealed at 910  C. Also the Al73Co10Mn17 annealed at 800 or 910  C consisted of the single 4-phase of slightly different lattice parameters (see Table 1). The further continuity of the compositional region of the 4-phase and Al5Co2 reported in Ref. [14] was not examined in the present work. It is plausible due to their same crystal structures mentioned above. The solubility of Co in the l-phase is probably low, similar to that of Cu and Ni. Monoclinic M-Al13Co4 (see Table 1), the only phase known in 1970s close to this composition, strongly propagates into the ternary compositions, while the other AleCo structures forming at close binary compositions were not revealed in the studied samples. The powder XRD pattern of the M-phase containing 10.5 at.% Mn is shown in Fig. 9c and the corresponding lattice parameters are provided in Table 1. At 910  C the AleMn T-phase was found to dissolve at least 2.5 at.% Co.

3.6. AleFeeMn The Al-rich part of AleFeeMn was systematically studied in the recent Ref. [21]. The representative part of the isothermal 875  C section is shown in Fig. 2d. Al13Fe4 is isostructural to the above-mentioned monoclinic MAl13Co4 and also dissolves up to ~15 at.% Mn. In contrast to Al5Co2, Al5Fe2 (whose structure is different from that of Al5Co2) only dissolves up to 11.5 at.% Mn. However, similar to Co and Ni, also Fe stabilizes the metastable AleMn 4-phase, which is formed between Al77Mn21Fe2 and Al74Mn15Fe11 depending on temperature. The AleMn T-phase dissolves up to 14.5 at.% Fe, i.e. significantly more than Co or Ni and comparable to the Cu solubility in this phase (see above). This visibly increases its upper existence temperature limit and decreases its lower existence temperature limit: at 875  C the T-phase is already unstable in binary AleMn and its ternary region is disconnected from the binary terminal. The compositional regions of the T-phase and 4-phase are separated by that of the n-phase extending up to ~5 at.% Fe. On the other hand, l and m only dissolve a little Fe. The extension of the Al6Mn up to ~8 at.% Fe was revealed. Close to the upper-Fe limit of the m-phase region, the ternary zphase isostructural to the AleNieMn z-phase was revealed (see Table 1).4 The AleMn D3-phase is also stabilized by Fe. Stable D3 was observed at a lower-Mn margin of the ternary extensions of the T-phase. An additional Z-phase of unknown structure was found around Al81.7Mn9.8Fe8.5 between 737 and 796  C (i.e. below that of the section in Fig. 2d). Its composition is close to a hypothetical Al9(Fe,Mn)2, but the suggested Al9Co2-type structure was not confirmed by powder XRD.

4 Apart from the basic reflections corresponding to the structural model of Ref. [20], weak additional reflections were revealed in the electron diffraction patterns. Their nature is unclear.

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Al

a)

b)

L

Al

L

10

20

10

90

90

Al9Co2

μ

ν

Al9Co2

ζ

Al5Co2

φφ 10

20

Co at.%

80

M

Al13Co4

M T

20 μ

80

ν

Al13Co4

φ

10

Al5Co2

20

Co at.%

Fig. 8. Results of the present experiments on AleCoeMn (black lines) in comparison to the isothermal sections of Ref. [14] (blue lines): a) at 900  C, b) at 800  C. The compositions of the studied samples are marked by solid squares, the measured compositions of the phases are marked by open squares, provisional lines are broken, L is liquid. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Intensity, (a.u.)

a

b

c

d

10

20

30

2θ, (°)

40

50

Fig. 9. Powder XRD patterns (Cu Ka1-rad.) of: a) the 4-phase of Al74.7Co3.7Mn21.6 annealed at 910  C for 93 h, b) the 4-phase calculated using the data of Ref. [53], c) the M-phase of Al76.6Co12.9Mn10.5 annealed at 800  C for 163 h, d) the M-phase calculated using the data of Ref. [54].

3.7. AleZneMn The 600  C isothermal section of AleZneMn reported in Ref. [23] (blue lines and symbols in Fig. 2e), being the most informative literature source, was accepted as a basis for the further improvements. The compositions of the phases reported in other studies are also displayed in Fig. 2e. The extended region of the “blue” t1 includes the compositions reported in Ref. [8] for TZn1 and TZn2. This followed from the similarity of the powder XRD patterns collected but not decoded in Ref. [23]. Earlier several mutually related unit cells were proposed for TZn1. In Ref. [9] an orthorhombic structure with a ¼ 2.51, b ¼ 2.48,

c ¼ 3.03 nm was concluded from the single-crystal XRD study of Al24ZnMn5 (Al80Zn3.3Mn16.7). In Ref. [11] a body-centered orthorhombic so-called L-phase with a ¼ 1.24, b ¼ 1.26, c ¼ 3.05 nm (i.e. with similar c but a and b half as small) was observed at the same composition by electron diffraction in TEM. The latter structure, containing numerous defects, was found to transform by annealing to a well-ordered monoclinic phase with a ¼ c ¼ 1.77, b ¼ 3.05 nm and b ¼ 89.1 (90.9 according to convention). The latter is almost orthorhombic with one of the linear parameters close to that in Ref. [9] and two others √2 times smaller. These observations allowed to suggest the similarity of this phase to the so-called AleCr h-phase (Al11Cr2 or Al5Cr, see Ref. [42] and references therein). Although in binary AleCr it is formed at somewhat higher Al concentrations, it was also observed down to 80 at.% Al in AleFeeCr [43].5 In Ref. [11] the same monoclinic structure was also observed in Al12ZnMn2.9 (Al75Zn6.3Mn18.2) which is rather closer to the composition of the TZn2-phase. Thus, the results of Ref. [11] are consistent with the compositional range of the “blue” t1. Its similarity to the AleCr h-phase was confirmed in our experiments (see below). It is worth noting that ~84% of Cr can be replaced in this structure by Mn [39]. Alternatively, the phase which was reported in Ref. [23] at somewhat higher Mn concentration (blue t2, in Fig. 2e) could be associated with TZn2 of [8]. As to “blue” t4, studied by powder XRD but not identified in Ref. [23], its diffraction patterns resembled those of high-temperature T-Al3Mn, which was also confirmed in our experiments (see below). On the other hand, the XRD pattern of t3 reported in Ref. [23] resembles that of D3 rather than of R reported in Ref. [10] for the TZn3 phase detected at a close composition (compare the middle pattern in Fig. 2b of Ref. [23] to our Fig. 3f). In our experiments alloys expected to contain t1, t3 and t4 of Ref. [23] were annealed in sealed ampules at 600  C for 240 h. The measured compositions of the phases were consistent with the compositional regions of the phases in Ref. [23]. The powder XRD pattern of a sample containing the major phase of Al74.4Zn9.0Mn16.6 (close to the lower-Al limit of “blue” t1) was successfully indexed using the AleCr h-phase prototype (see Appendix D). This pattern in Fig. 10a is compared to that in Fig. 10b calculated from the model

5 In several reports it was even suggested that this structure belonged to a ternary orthorhombic AleFeeCr phase with lattice parameters very close to those of the above-mentioned L-phase of Ref. [11], but later it was concluded to be a ternary extension of the AleCr h-phase (see Ref. [43] and references therein).

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for a definite assertion of the diffraction pattern to be a quasiperiodic structure due to the existence of periodic structures exhibiting very similar patterns (see Ref. [43], for example). As in the case of AleCueMn, electron diffraction or XRD from a single grain is essential. No systematic search for this phase was carried out in our experiment. It is also plausible that the cubic g3-phase reported in Ref. [23] at lower-Al concentrations is actually the ternary extension of the high-temperature AleMn g1-phase (see Fig. 1) stabilized at lower temperatures by Zn. The cubic structure of the latter is argued in Ref. [45]. A decrease of the transition temperature of the reactions between g1 and g2 with the addition of Fe was revealed in Ref. [21] by differential thermal analysis, while in AleCueCr the AleCr g1phase was directly detected by powder XRD [38].

Zn Al

Intensity, (a.u.)

a

Zn

b

c

3.8. AlePdeMn

d

10

157

20

30

2θ, (°)

40

50

Fig. 10. Powder XRD patterns (Cu Ka1-rad.) of: a) the h-phase of Al74.4Zn9.0Mn16.6 coexisting with the liquid in a sample annealed at 600  C for 240 h (the Al and Zn lines correspond to the solidified liquid), b) the AleZneMn h-phase calculated using the data of Ref. [44], c) the T-phase in Al66Zn16Mn18 annealed at 600  C for 240 h, d) the AleZneMn T-phase calculated using the data of Ref. [28].

of Ref. [44], where the Mn atoms are placed at the Cr positions and the Zn atoms at the Fe positions. Due to the structural similarity also this AleZneMn phase will be designated h. The powder XRD patterns of a sample containing the single phase of Al66Zn16Mn18 typical of “blue” t4 was successfully indexed using the T-phase prototype. This pattern in Fig. 10c is compared to that in Fig. 10d calculated from the model of Ref. [28]. Therefore, the “blue” t4-phase is actually the ternary extension of the AleMn Tphase stabilized by Zn at lower temperatures. This is supported by the examination of solidified samples, where the grains of Al68.6e70Zn5.5e6.5Mn24e25.5 were identified with the T-phase. The ternary extension of the T-phase is also spread to higher Al concentrations. In a sample annealed at 500  C the single T-phase had a composition of Al75.8Zn4.0Mn20.2. The strong decrease of the lowertemperature stability limit of the T-phase at ternary compositions was already mentioned above in AleCueMn and AleFeeMn. A sample of an intermediate composition, expected to contain “blue” t3, revealed the coexistence of the h-phase and the T-phase, identified by powder XRD. The h-phase was of Al73.5Zn8.8Mn17.7 and the T-phase of Al68.5Zn13.1Mn18.4. This observation contradicts the equilibrium concluded in Ref. [23]. An additional minor phase was observed close to the latter composition at a slightly lower-Mn concentration. It could belong to “blue” t3. No single-phase sample containing t3 was obtained in our work, but its association with the R-structure of Ref. [10] is plausible. The grains of this phase were extracted in Ref. [10] from the matrix and studied by singlecrystal XRD and their compositions were determined in two external laboratories. The observation of the typical XRD pattern of D3 in Ref. [23] at a composition earlier reported for the R-phase requires further clarification. This might be an additional phase forming in this system at another composition. Apart from this, according to the authors' experience, powder XRD is not sufficient

The coexistence and mutual relations of the T-phase and Rphase were extensively studied in AlePdeMn, where the R-phase was at first suggested to be metastable, but its thermodynamic stability was concluded and its compositional region specified in Ref. [46] (see Fig. 5b). Although Pd belongs to the same column of the periodic table as Ni, the constitution of the AlePdeMn alloy system close to the AleMn terminal is more similar to that of AleCueMn than that of AleNieMn. The AleMn T-phase dissolves up to 7.5 at.% Pd, which visibly decreases its lower existence temperature limit. At ternary compositions it was observed down to at least 650  C and below 895  C its ternary region is disconnected from the binary terminal [46]. The R-phase is stable below 720  C in a small region with somewhat lower Mn than the T-phase (~Al80Pd5Mn15). The compositional differences of coexisting T and R were not revealed in metallographic samples and are probably very small. In as-cast samples examined by TEM the T-, R- and D3-phases were often observed coexisting in the same grains building complex domain structures. The l and m phases only dissolve a little Pd. Both the AleMn decagonal D3-phase and the icosahedral I-phase are stabilized by Pd. The typical composition of stable D3 is Al70Pd13Mn17 and the Iphase is stable in a compositional region of 5.8e10.5 at.% Mn and 69.5e71.5 at.% Al, depending on temperature [47]. 3.9. Orthorhombic R and T vs. hexagonal 4 and z In the ternary AleTMeMn alloy systems containing Fe, Co or Ni the z-phase was revealed adjacent to Al4Mn. In contrast, in AleTMeMn containing Cu and Pd the R-phase was revealed adjacent to Al4Mn and in AleZneMn there was the h-phase. However, the Rphase is also formed in the latter, but at somewhat lower Al concentrations. Together with the formation of the z-phase, also the stabilization of the metastable AleMn 4-phase by Fe, Co or Ni occurs. In the systems with Ni and Co the propagation of the binary T-phase was visibly suppressed in favor of the 4-phase, while in AleFeeMn the 4-phase and T-phase mutually limit their compositional regions (see Fig. 2). On the other hand, in Ale(Cu, Zn or Pd)eMn ternaries the 4-phase was not stabilized, while the regions of the T-phase were found to extend widely to ternary compositions. Thus, there are either T þ R or 4 þ z combinations are typical of the studied ternary alloy systems. The T-phase and R-phase have very close lattice parameters c and the volumes of their unit cells. Accordingly, bR/aT z bT/aR and this ratio is close to the golden mean t ¼ (√5 þ 1)/2. As follows from the analysis of their structures and as is demonstrated by HRTEM images of the planes perpendicular to the c-axis, the R- and T-phases are constructed from the same building elements

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arranged parallel in R and in a herringbone manner in T. This matter was extensively studied in AlePdeMn (see Ref. [16] and references therein). In the AleCueMn and AlePdeMn phase diagrams the ranges of the R-phase and T-phase, located very close to each other, could not be reliably separated. The observation of the metastable binary AleMn p-phase points to a possibility that the stable ternary R-phases also have a binary origin and are stabilized by Cu (which was already suggested in Ref. [32]) or by Pd and Zn atoms, but not by Ni, Co or Fe. TEM examinations of rapidly solidified AleMn alloys [32] revealed the coexistence of the R- and T-type structures similar to that in AlePdeMn. It is reasonable to suggest that both these orthorhombic phases are stabilized by the same factors in ternary systems, while the replacement of Cu or Pd by Ni, Co or Fe is favorable for their destabilization in favor of the stabilization of the hexagonal 4- and z-phases. In a trial to find a regularity in the formation of ternary compounds revealed close to Al4Mn in the systems with Ni, Cu and Zn, Raynor pointed to their close electron-to-atom ratio e/a z1.85 [8]. This was based on their compositions known at that time and implied their structural similarity, which was not confirmed in more recent investigations. However, the importance of the electron concentration can be demonstrated with other examples. Thus, in AleCueMn the Al-concentrations of the R-phase and Tphase are lower than in AlePdeMn and extend towards still lower Al with increasing Cu concentration. This tendency is even stronger in AleZneMn. The addition of an element with a positive valence (þ1 for Cu and þ2 for Zn) requires a reduction of the concentration of three-valent Al in order to maintain the electron concentration, i.e. Cu or Zn (but not Pd) replace Al. On the other hand, the compositional regions of the z-phases extend at practically constant Al with the addition of Fe, Co or Ni, whose valences have higher values than that of Mn but are still negative, implying the replacement of Mn by these elements. Similar tendencies were observed in Ale(Cu, Ni or Pd)e(Fe, Co, Ru or Rh) ternaries and discussed in Ref. [48] and references therein. 3.10. Decagonal phases All known binary Al-based quasicrystals are metastable, but in several ternary systems they were found to be stabilized [48]. In AleMn the decagonal phase belongs to the D3-type (periodicity ~1.2 nm in the specific direction) [34]. Such a periodicity is also typical of the T and R phases in the direction perpendicular to the pseudo-decagonal plane, and is also typical of the z and l phases in the c-directions (see Table 1). While the decagonal structures with other periodicities in the specific directions were also reported in Al-based alloy systems [48], the stable decagonal phases observed in AleFeeMn, AlePdeMn, AleCueMn and also in AleFeeCr [43] are of the D3-type. Attempts to find a stable D3-phase in AleNieMn were not successful, but a metastable D3-phase, as was mentioned above, was observed together with the O-phase in samples solidified at natural cooling rates [18]. We have no information on such trials in AleCoeMn. In the above-mentioned systems stable D3 was observed to coexist with a lower-Mn margin of the wide ternary extensions of the T-phase, while in AleNieMn and AleCoeMn, where the ternary extensions of the T-phase are not developed, no stable decagonal phase was observed. Probably the same factors are favorable for the stabilization of D3 and T at ternary compositions. According to the above-mentioned TEM observations of as-cast AlePdeMn alloys, the D3-phase coexisted in the same grains with T and R. Due to the suggested structural similarity, they probably have very close formation energies. In view of the noticeable similarity of the constitutions of the Alrich regions of AleMn and AleCr, particularly manifested in the

structure of the ternary AleCreMn phase diagram [39], it is worth mentioning the observations of the T, R and D3 structures also in AleCueCr. In the latter, in contrast to AleCueMn, the stable ternary phase forming adjacent to Al4Cr has a z-type structure, the AleCr D3-phase is not stabilized by Cu and the T-phase, which does not exist in AleCr, is also not among the stable phases in AleCueCr [38,49]. However, in experiments described in Refs. [50e52] the T, R and D3 structures were observed in the same AleCueCr alloys. The decagonal phases (apart from D3 also D9 was reported) were even concluded in Ref. [50] to be stable since they were observed in an Al70Cu10Cr20 alloy annealed at 1000  C. However, this temperature is considerably above the melting temperature of the alloy, and in other experiments in Refs. [50e52] the materials were also heated above their melting points. This allowed us to conclude that the T, R and D3 structures, not observed in the isothermal sections of AleCueCr [38,49], were formed from the liquids solidified at natural cooling rates. A more detailed study of this matter is in progress. In AleZneMn metastable D3 was produced at Al75.5Zn6.3Mn18.2 [11] by melt spinning and by additional heating it was transformed to the h-phase. However, considering the known constitutions of the Ale(Fe, Cu or Pd)eMn ternary alloy systems, the D3-phase would be expected to be stabilized at somewhat lower Mn and much lower Al concentrations. 4. Conclusions  The solubility of Fe, Co, Ni, Cu, Zn and Pd in m-Al4Mn and lAl4Mn is low.  The high-temperature T-Al3Mn dissolves up to at least 14.5, 12, 16 and 7.5 of Fe, Cu, Zn and Pd, respectively.  The metastable 4-Al10Mn3 is stabilized by Fe, Co and Ni in wide ternary compositional regions, and in AleCoeMn such a region propagates up to Al5Co2.  In alloys with Fe, Co and Ni the ternary hexagonal so-called zphase (P63/m, a z 1.76, c z 1.25 nm) is formed along ~80 at.% Al.  In alloys with Cu and Pd the orthorhombic so-called R-phase (Bbmm, a z 2.41, b z 1.25, c z 0.76 nm) was found at similar compositions.  In the quaternary AleCueNieMn z-phase containing ~14.5 at.% Mn at least 65% of Ni can be replaced by Cu, while in the quaternary R-phase up to 20% of Cu can be replaced by Ni.  The R-structure is also formed in AleZneMn but at lower-Al concentrations, while in the range of 75e80 at.% Al a monoclinic phase so-called h-phase (C2/c, a z 1.76, b z 3.04, c z 1.76 nm, b z 90 ) is formed.  In addition to the stable decagonal D3-phase in AleFeeMn and AlePdeMn reported earlier, the stabilization of binary AleMn D3-phase was also revealed in AleCueMn around Al64Cu20Mn16.  Either T þ R or 4 þ z combinations are typical of the studied ternaries. Acknowledgements The authors thank C. Thomas for technical contributions. Appendix A Diffraction data of the AleCueMn T-phase (Al70Cu11.5Mn18.5, Pnma, a ¼ 1.46256(6), b ¼ 1.24557(4), c ¼ 1.25469(6) nm). From the total of 90 collected reflections only those with I/I0  4% are given. The indexing is for the best fit (aver. D(2q) ¼ 0.005 , max. D(2q) ¼ 0.027, FOM(30) ¼ 46.8).

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162

159

(continued ) No.

h

k

l

d

1 2 3

1 0 2 2 1 3 2 1 3 1 3 2 4 4 2 4 1 4 0 5 2 6 5 6 2 4 0 5 1 6 5 3 0 6 0 5 1 4 7 2 5 2 0 7 1 2 2 6 3 9 1 4 5 7 9 6 6 2 5 3 2 3 3 8 7 8 4 11 1 10 6 0 7 0 1

0 1 0 1 0 0 2 2 0 1 1 3 0 1 3 1 2 3 5 0 3 2 2 1 2 4 5 0 5 3 4 5 0 1 6 3 0 0 0 3 2 0 2 0 5 2 5 3 1 2 6 6 3 6 1 8 1 5 8 7 8 5 3 7 5 5 7 0 9 5 6 0 0 10 11

1 1 1 0 2 1 1 2 2 3 2 0 1 0 1 1 3 2 1 3 4 0 3 2 5 2 3 4 3 0 1 2 6 3 0 3 6 5 1 5 4 6 6 2 4 6 4 6 8 3 6 5 7 2 4 0 8 8 3 6 5 8 9 0 6 5 6 3 4 0 6 10 8 0 3

0.95226 0.88392 0.63150

43 87 46

0.57651 0.45444 0.44354 0.42308 0.38477 0.38266 0.36777 0.36104 0.35085

48 34 45 63 56 103 95 70 52

0.34696 0.33751

112 95

0.25152 0.24418 0.23964 0.23685 0.22701 0.22368

43 81 46 58 145 301

0.22179

246

0.21396

64

0.21176 0.21021

354 371

0.20914

607

0.20758

1000

0.20691

460

0.20603

899

0.20233 0.20105 0.19824

47 47 303

0.19335 0.19133 0.18859 0.14825

58 43 38 53

0.14722 0.14656

71 89

0.14337

108

0.13121

42

0.13057

99

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

27 28 29 30 31 32 33 34 35 36 37 38

39 40

41 42 43 44

45 46

47 48 49

I

No.

h

k

l

d

50

8 9 13 4 11 5 0 5 7 7 4

6 3 3 11 6 4 6 9 6 1 5

7 8 1 0 3 10 10 6 8 10 10

0.10892

51

0.10816

47

0.10736

58

0.10715

47

51

52

53

Appendix B Diffraction data of the AleCueMn R-phase (Al77.9Cu8.5Mn13.6, Bbmm, a ¼ 2.41023(15), b ¼ 1.24787(8), c ¼ 0.76102(7) nm). From the total of 96 collected reflections only those with I/I0  5% are given. The indexing is for the best fit (aver. D(2q) ¼ 0.005 , max. D(2q) ¼ 0.046 , FOM(30) ¼ 94.4). The sample of Al80Cu8Mn12 contained some (Al).

No.

h

1 2

2 2 3 1 4 3 5 5 6 0 2 1 4 3 0 4 7 2 8 9 6 1 5 9 1 2 3 10 2 6 3 3 10 4 7 5 8 9 1 5 6 11 3 10 0

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

19

0.13018 0.12806 0.12755

96 129 43

0.12709

121

0.12671 0.12613

129 60

0.12544

164

0.12455 0.10900

53 58

I

20 21 22 23 24 25 26 27 28

29 30 31 32 33 34 35

k 1 2 0 2 2 2 0 1 1 0 0 3 3 3 2 0 0 2 1 0 2 0 4 1 1 5 0 1 4 3 5 2 2 4 4 1 2 3 3 5 5 0 3 3 6

l

d

0 0 1 1 0 1 1 1 0 2 2 1 0 1 2 2 1 2 0 1 2 3 1 1 3 0 3 0 2 2 1 3 0 2 1 3 2 1 3 1 0 1 3 0 0

0.86661 0.55281

I 121 199

0.47306 0.43338 0.41362 0.40722 0.38710 0.38217 0.38125 0.36266 0.36090 0.34231 0.33230 0.32483 0.32173 0.31371

86 158 99 55 119 93 55 104 204 80 156 61 59 77

0.29286 0.25262

52 72

0.24760

75

0.24435 0.24187 0.23650

168 64 133

0.23013 0.22745 0.22553 0.22483 0.22400 0.22097

87 136 345 208 87 191

0.21592

102

0.21279 0.21199 0.21057 0.20911 0.20864 0.20799

499 355 495 769 273 359

(continued on next page)

160

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162

(continued ) No.

h

k

l

d

I

No.

h

k

36

2 8 7 10 12 4 7 10 8 12 3 0 2 3 8 11 7 5 9 10 2 15 0 4 7 6 15 16 9 1 15 3 12 6 8 15 16 13 10 5 9 18 0 7 18 12 2 5 15 14 11 14 10 18 17 6 12 17 5 15

5 3 0 1 0 5 5 2 5 2 4 0 5 8 3 6 6 8 7 7 8 4 6 8 2 8 0 3 8 8 2 8 3 9 8 3 5 5 5 8 7 3 0 9 0 4 1 5 6 2 0 7 8 2 0 7 8 1 10 5

2 2 3 2 0 2 1 2 0 0 3 4 4 1 4 1 3 1 1 0 2 1 4 2 5 2 3 2 1 3 3 3 4 0 2 3 0 3 4 3 3 0 6 1 2 4 6 5 1 4 5 0 2 2 3 4 0 3 1 3

0.20543

1000

0.20425 0.20090

377 82

1 2 3 4

0.19720 0.19530 0.19357 0.19219 0.19118

126 122 88 150 118

0.19026 0.15005

167 50

0.14797 0.14572

99 67

0.14332

51

0.14039

76

1 1 0 1 2 2 3 2 2 3 2 1 2 4 3 3 2 3 4 0 3 5 4 3 2 5 5 5 3 5 4 3 4 6 2 4 6 7 2 6 4 5 0 5 7 3 2 7 5 5 7 6 6 5 7 7 7 7 9 7 8 8 7 7 4 5 5 6 10 9 7 8

1 1 0 0 1 1 0 2 1 1 2 1 0 0 1 2 1 2 0 0 1 0 1 3 1 0 1 2 3 2 2 2 3 1 1 4 1 0 2 0 4 2 0 1 0 2 1 0 4 2 1 3 1 4 2 0 2 0 2 5 1 3 5 1 0 2 5 4 0 1 5 5

37 38 39 40 41 42 43 44 45

46 47

48 49

50

51

52

53 54 55 56

57 58 59 70

71 72

73 74

5 6 7 8 9 10 11 12 13 14 15 16 17

0.13582

53

18

0.13271

65

19 20

0.13108

114

0.13017 0.12899

78 91

0.12837 0.12811

124 81

0.12747 0.12684

50 80

0.12632

94

0.12547

103

30 31 32

0.12501

129

33

0.12382

71

21 22

23 24 25 26

27 28 29

34

35 0.12320

52

0.11925

59

36 37 38

Appendix C Diffraction data of the AleCoeMn z-phase (Al80Co3.1Mn16.9, P63/ m, a ¼ 1.76058(7), c ¼ 1.24638(3) nm). From the total of 84 collected reflections only those with I/I0  6% are given. (aver. D(2q) ¼ 0.004 , max. D(2q) ¼ 0.015 , FOM(30) ¼ 129.0).

39 40 41 42 43 44

l

d 0 1 2 2 0 1 1 0 2 0 1 3 3 1 2 0 3 1 2 4 3 1 2 0 4 2 0 0 3 1 3 4 2 0 5 0 2 0 5 3 1 3 6 4 2 5 6 3 1 4 2 0 4 2 0 4 2 6 2 0 5 3 1 6 8 7 5 5 3 4 2 0

I

0.88029 0.71902 0.62319 0.57660

91 103 115 184

0.52305 0.47062 0.44013 0.42305

138 93 62 151

0.41500 0.37572 0.36476

109 68 65

0.34985

156

0.33684

184

0.32518 0.31160 0.29632

84 68 61

0.29354

71

0.27399

78

0.24415 0.23965

108 100

0.23680 0.23261

75 240

0.22875 0.22007 0.21781

279 67 481

0.21681

665

0.21050 0.20773 0.20562

703 235 1000

0.20300 0.19539 0.19288

806 76 80

0.19216

72

0.18633

77

0.17853

95

0.15034 0.14606

68 83

0.14508

85

0.14481 0.14420 0.14383

99 77 72

0.14316

110

0.14219

106

0.13424

66

B. Grushko et al. / Journal of Alloys and Compounds 677 (2016) 148e162 (continued )

(continued )

No.

h

k

l

d

45

7 7 7 8 11 10 10 7 9 8 7 11 0 8 7 10 7 9 11

3 5 6 3 0 0 2 2 2 5 0 2 0 3 6 0 6 5 3

6 4 2 5 3 5 3 7 5 3 8 0 10 6 4 6 5 3 1

0.13224

66

0.13151

134

0.13007

119

0.12870

85

0.12774 0.12672 0.12576 0.12465 0.12413

261 322 208 128 68

0.12290 0.11889

87 67

46 47 48 49 50 51 52 53 54 55

I

No.

2 3 4 5

6 7 8 9

10 11

12 13

14

15 16

17

20 21 22

24

25

Diffraction data of the AleZneMn h-phase (Al74.4Zn9.0Mn16.6, C2/c, a ¼ 1.7615(1), b ¼ 3.0362(3), c ¼ 1.7598(2) nm, b ¼ 90.656(8) ). From the total of 68 collected reflections only those with I/I0  5% are given. The indexing is for the best fit (aver. D(2q) ¼ 0.004 , max. D(2q) ¼ 0.013 , FOM(30) ¼ 13.2).

1

18 19

23

Appendix D

No.

161

h 0 1 0 1 1 2 2 3 1 2 1 0 3 1 2 0 1 3 1 4 2 5 7 1 4 7 2 6 6 0 1 3 3 4 7 7 0 5 7 3

k 2 1 4 1 3 0 2 1 1 4 5 6 3 3 6 6 7 5 5 4 4 9 3 9 8 3 12 8 6 8 13 1 11 10 3 5 14 7 1 13

l

d 1 1 0 2 2 2 2 1 3 1 1 0 1 3 0 2 1 1 3 2 4 1 1 5 4 2 2 0 3 6 1 7 3 3 3 3 0 5 4 1

26 27

I

1.14880

91

0.75969

74

0.61936

185

0.57876 0.54535

70 92

0.50624 0.48919

81 128

0.43904

70

0.40972

53

0.35082

65

0.24160

72

0.23459

115

0.23213

93

0.22941

160

28

29

0.22460 0.21689

244 409

0.21545

407

30

31

h

k

l

1 5 1 8 6 8 0 6 7 2 1 3 7 2 1 8 4 7 1 9 3 4 5 5 11 3 1 2 10 13 5 4 13 11 9 13 7 3 1 6 11 11 4 10 13 8 10 13 2 2 0 1 5 10 5 4 8 9

13 11 11 2 10 2 10 0 5 10 13 1 7 14 15 4 6 11 17 7 11 14 13 19 1 13 19 0 8 3 17 2 7 11 13 5 13 15 21 20 3 13 20 16 7 6 6 7 8 24 24 9 21 0 9 14 20 17

3 1 5 2 0 2 6 6 4 6 4 8 3 2 1 3 7 3 0 1 7 4 4 1 5 9 5 12 5 3 8 13 0 5 7 3 9 10 6 4 8 3 6 0 1 11 9 3 13 0 2 13 5 10 12 11 2 5

d

I

0.21204 0.21104

514 357

0.20873 0.20643 0.20473

57 259 1000

0.19968

170

0.17765

52

0.14495

61

0.13123 0.12931

76 146

0.12911

115

0.12601

319

0.12523

213

0.12387

67

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