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Phase equilibria in the Ni-Mn-Sb alloy system
Accepted Manuscript Phase equilibria in the Ni-Mn-Sb alloy system T. Miyamoto, M. Nagasako, R. Kainuma PII:
S0925-8388(18)33263-8
DOI:
10.1016/j.jallcom.2018.09.035
Reference:
JALCOM 47454
To appear in:
Journal of Alloys and Compounds
Received Date: 2 July 2018 Accepted Date: 3 September 2018
Please cite this article as: T. Miyamoto, M. Nagasako, R. Kainuma, Phase equilibria in the Ni-Mn-Sb alloy system, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2018.09.035. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 2018/07/02 For submission to J. Alloys. Compd.
T. Miyamoto1, M. Nagasako2 and R. Kainuma1*
1
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02
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Aoba, Sendai 980-8579, Japan. 2
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Phase Equilibria in the Ni-Mn-Sb Alloy System
Institute for Materials Research (IMR), Tohoku University, 2-2-1 Katahira, Sendai 980-8577,
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Japan.
Abstract
Phase equilibria and ordered phase regions in the Ni-Mn-Sb system at 700 and 900 °C and the martensite phase region at room temperature were determined mainly by the diffusion triple method.
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It was confirmed that single-phase region of the ordered bcc phases exists in a wide composition range of a central part at both 700 and 900 °C and that the region is divided into two regions of
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half-Heusler C1b and full-Heusler L21 at 700 °C, while the C1b phase is missing at 900 °C. The B2 + L21 phase separation was also confirmed in a certain composition range near Ni-50%Mn, and the
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iso-Ms (= RT) line in the L21 phase region was also estimated to be located from 12 to 16 at.% Sb.
Keywords
Phase diagram; Ni–Mn–Sb; martensitic transformation; magnetic shape memory; order–disorder transition; Heusler alloy
*Corresponding author. Tel.: +81 22 795 7321; fax: +81 22 795 7323. E-mail address: [email protected] (R. Kainuma).
ACCEPTED MANUSCRIPT 1. Introduction In the Ni-Mn-Sb system, there are three kinds of similarly ordered bcc phases, the NiMn phase with the B2 (Pm-3m) structure, the full-Heusler (FH) Ni2MnSb phase with the L21 (Fm-3m) structure, and the half-Heusler (HH) NiMnSb phase with the C1b (F-43m) structure. The
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HH-NiMnSb alloy is a candidate for half-metallic ferromagnets in spintronic devices [1] and the off-stoichiometric FH-Ni2MnSb alloy a ferromagnetic shape memory alloy [2-4]. Figure 1 shows a schematic illustration of the ordered bcc structures comprising four equivalent FCC sublattices: A, B,
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C and D. In the FH-Ni2MnSb structure, the Ni atoms occupy both the A and C sites, and the Mn and Sb atoms enter to the B and D sites, respectively. If the Ni2MnSb alloy has a B2-Ni(Mn,Sb) structure,
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the Mn and Sb atoms randomly occupy both the B and D sites. In the HH-NiMnSb structure, however, the C site, which is one of the Ni sites in the FH structure, is occupied by vacancies and an ordering of vacancies, i.e., the order-disorder transition from the L21 to the C1b, occurs during cooling in the NiMnSb ternary alloy [5]. Although phase equilibria and stability, including the
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order-disorder and martensitic transformations, are important, the ternary phase diagram in the Ni-Mn-Sb system remains unknown.
Figure 2 shows the Ni-Mn [6,7], Mn-Sb [8] and Ni-Sb [9] binary phase diagrams. In the Ni-Mn
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system, a single phase region of γ with disordered fcc: A1 (Fm-3m) structure exists in a wide composition range and a B2-NiMn phase appears in the temperature range 700-1000 °C near the
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stoichiometric composition. However, in the Ni-Sb and Mn-Sb systems, some intermetallic compounds, such as B81-NiSb (P63/mmc), Ni5Sb2 (C121), D0a -Ni3Sb (Pmmn), B81-MnSb (P63/mmc), and C38-Mn2Sb (P4/nmm) exist with a limited solubility. From this information, the NiSb phase region is expected to connect directly to the MnSb phase with the same crystal structure. Recently, the experimental phase diagram in the Ni-Mn-In system was effectively determined by using the diffusion triple (DT) method [10,11], which is a combinatorial technique to effectively estimate the equilibrium compositions [12]. In the present study, the phase equilibria at 700 and 900 °C in the whole region of the Ni-Mn-Sb
ACCEPTED MANUSCRIPT ternary system and the critical compositions of B2 / L21 and L21 / C1b order-disorder transformations are determined by using the DTs, diffusion couples (DCs) and multi-phase alloys. Furthermore, the composition region where the martensite phase exists at room temperature is evaluated.
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2. Experimental procedures 2-1. Multi-phase alloys
In the present study, the obtained DTs covered a composition range limited to the Ni-Mn side in the
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ternary system. Therefore, many alloy samples were prepared as listed in Tables 1 and 2. The samples were induction-melted from pure Ni (99.9%), Mn (99.9%), and Sb (99.5%) and annealed for
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equilibration at 700 °C for 72h and at 900 °C for 30 h in quartz tubes under an argon atmosphere. Microstructural observation was carried out by scanning electron microscopy (SEM) and the equilibrium compositions were determined by electron probe microanalysis (EPMA). 2-2. Diffusion couples and triples
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The DTs ware prepared by the same method as reported in the Ni-Mn-In [11] and Co-Fe-Ga [13] systems with the following three steps [11]:
(1) Ni/Mn and Ni/Ni-75at%Mn DCs, which were joined with induction melting, were
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diffusion-annealed at 1000 °C for 168 h in evacuated quartz tube to obtain a continuous diffusion zone between the Ni and Mn or Ni-75%Mn blocks.
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(2) A 3-mm-diameter cylindrical hole was formed by electric discharge machining near the diffusion zone of the binary DCs and some Sb chips were inserted into the hole. DTs were finally obtained by diffusion-annealing at 700 °C for 24 h and at 900 °C for 1, 3, or 12 h in evacuated quartz tubes. (3) The obtained DTs were cut from a section vertical to the Sb cylinder and chemically analyzed by EPMA along lines parallel to the Ni/Mn interface. The phase equilibria were determined by using the Ni/Mn/Sb DT samples, and the existing region of the martensite phase at room temperature was evaluated by EPMA from microstructures in the
ACCEPTED MANUSCRIPT Ni/Ni-75%Mn/Sb DT. To determine the critical composition of the L21/C1b order-disorder transition, Ni2MnSb/NiMnSb DCs were also prepared by the melting method, in which the Ni2MnSb block laid on a NiMnSb block in the evacuated quartz tube was heated at 1100 °C (over the melting points of both alloys) for a very short duration of approximately 180 s in an electric furnace and the two
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blocks were joined together without intermixing the master alloys, followed by air-cooling. The
then analyzed by EPMA.
3. Results and discussion
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3-1. Isothermal section diagrams of 700 and 900 °C
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obtained DCs were annealed at 600, 700, 800 and 900 °C for 74, 32, 18 and 10 h, respectively, and
Figure 3 shows the SEM image near diffusion zone in the DT specimen annealed at 900 °C for 3 h, where three distinct regions, Ni-rich γ, Mn-rich B2 and Sb-rich liquid (L) phases, are observed on the lower-left, upper-left and right sides, respectively. Moreover, an additional region with a gray
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contrast labeled by Μ is observed. This region has a typical microstructure of martensite phase with a light gray contrast. Equilibrium compositions among those phases were determined using concentration-penetration profiles obtained by EPMA for the DTs annealed at 700 and 900 °C.
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Figure 4(a) and (b) shows typical concentration-penetration profiles for Mn and Sb elements near the diffusion zone in the DT specimen annealed at 900 °C for 12 h. Phase equilibrium concentrations
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were determined by extrapolating the concentration profiles to the phase interface, as demonstrated in Figure 4(a). The results of equilibrium compositions obtained from the DT samples annealed at 700 and 900 °C are listed in Tables 3 and 4, respectively. Because it is difficult to determine three-phase and solid-liquid-phase equilibria using the DT method, alloy samples with multi-phase structure were prepared and analyzed. The typical microstructures obtained from these specimens are shown in Figure 5. Phase equilibrium concentrations were determined from the average EPMA data obtained from at least different five points for each phase. All the results obtained from alloy specimens annealed at 700 and 900 °C are listed in Tables 1 and 2, respectively.
ACCEPTED MANUSCRIPT Figure 6(a) and (b) shows isothermal section diagrams for 700 and 900 °C, respectively, determined by the present study. The phase equilibria determined by the DT method are basically coincident with those by the alloy method. Both the isothermal diagrams for 700 and 900 °C have the same topological constitution in phase equilibria and all the phases, except the L21 (and C1b)
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phase at 700 °C, continue from each binary system. Contrary to expectations, the NiSb phase region does not directly connect to the MnSb phase even though both phases have the same B81 structure. It is important to note that the L21 + B2 two-phase equilibrium exists in the Ni-Mn-Sb system but not
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in the Ni-Mn-In system [11]. The origin of this difference is unknown, but because almost all the tie-lines from the B2 to the L21 or C1b phase are directed to Ni:Mn:Sb=1:1:1 composition, the phase
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separation may be related to the high thermodynamic stability of the C1b (or L21) phase in the NiMnSb composition region. From these results, one can construct a vertical diagram for the 50%Ni section (Figure 7). Interestingly, the L21 + B2 phase separation appears at a low temperature even in this section, although the continuous ordering transformation exists at 900 °C as demonstrated in the
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concentration-penetration profile without any concentration step [14] (Figure 4[b]). The L21 + B2 phase region drastically widens with decreasing Ni composition as expected (Figure 6). We have observed a dual-martensite structure comprising two phases, i.e., the L21 and the B2, with different
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transformation temperatures in 47%Ni alloys [15]. The details of these alloys will be presented in another paper. Another interesting issue is the locations of the L21 and C1b phase regions. As shown
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in Figure 6, both the regions are perfectly unified and it is difficult to distinguish each other from the shape of the single-phase region in the isothermal section diagram. The vertical diagram of the Ni2MnSb/NiMnSb section will be presented in the next section. According to the Ni-Sb binary phase diagram shown in Figure 2 [9], two binary compounds—Ni5Sb2 and Ni3Sb—should independently exist at 700 °C. However, these phases cannot be distinguished at 700 °C in the present study.
3-2. Order-disorder transformation between L21 and C1b
ACCEPTED MANUSCRIPT Order-disorder transformation from the L21 to C1b phase, that is, ordering of vacancies cited in A and C positions of the L21 structure, have recently been investigated by the present authors in Ni2-xMnIn alloys and the order-disorder transformation temperatures Tt L21/C1b have been determined by differential scanning calorimetry (DSC) [5]. Figure 8 shows the SEM images and the
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corresponding concentration profiles of Sb and Ni near the diffusion zone in the Ni2MnSb/NiMnSb diffusion couples annealed at 600 °C (a), 700 °C (b), 800 °C (c) and 900 °C (d). Although they show a left-right symmetry at 900 °C, at other annealing temperatures, the profile shapes lose this
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symmetry and a singular point appears. In general, such a point corresponds to a critical composition of continuous ordering transformation, such as A2/B2 and B2/D03 [14]. In this case, the profile
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gradient in the ordered phase region is always larger than that in the disordered phase, as demonstrated in the B2/L21 ordering shown in Figure 3(b) because of differences in the interdiffusivity of solute elements. From this perspective, it is obvious that the singular point corresponds to critical composition of L21/ C1b ordering transformation. The compositions at the
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singular point are consistent with the order-disorder transformation temperatures evaluated by DSC in our previous paper (Figure 9) [5]. From this result, the C1b phase should exist at 700 °C, but not at 900 °C (Figure 6[a]). Using the gradient of profile and Fick’s first diffusion law, the diffusivity of the
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C1b phase is concluded to be lower than that of the L21 phase. This relationship is very likely because the site occupancy of vacancies in the C1b phase is limited to Sublattice C, unlike that of the
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L21 phase, which appears in Sublattices A and C (Figure 1). This diffusivity tendency is proved also by an obvious difference in mean grain size between the L21 and C1b regions in the SEM images, that is, the mean grain size in the C1b region is clearly smaller than that in the L21 region (Figure 8[a] and [b]).
3-3. Existing region of martensite phase The pseudo-interface between the parent and the martensite phases as shown in Figure 3 corresponds to the region with the martensitic transformation temperature at room temperature.
ACCEPTED MANUSCRIPT Unfortunately, only limited information was extracted from the DTs with the Ni/Mn/Sb combination. A different DT sample fabricated from Ni/Ni-75%Mn/Sb was therefore prepared and examined. Figure 10(a) shows a typical microstructure near the diffusion zone of the DT specimen. The martensite phase region, with a gray contrast and a lamellar morphology, is recognized and the
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pseudo-interface is clearly detected, as indicated with a blue line. The iso-Ms = RT line (here, Ms is martensitic transformation starting temperature) was evaluated by EPMA analysis for the DT sample (Table 5; Figure 10(b)). Figure 7 shows that the Ms in the 50%Ni section estimated from the iso-Ms
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line is near the Ms temperature line reported by Sutou et al. [2]. The accuracy of the iso-Ms = RT line determined by this method may not be very high, but we can easily estimate the composition region
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with the same Ms temperature of 25 °C. The iso-Ms (= RT) line in the L21 phase region was estimated by this DT sample to be located from 12 to 16 at.% Sb (Figure 10[b]).
4. Conclusion
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The phase equilibrium compositions at 700 and 900 °C in the Ni-Mn-Sb system were determined using DTs and multi-phase alloys. It was confirmed that single-phase region of the ordered bcc phases exists in a wide composition range of a central part and that the region is divided into two
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regions of C1b and L21 at 700 °C. However, the B2 + L21 phase separation was confirmed in a wide composition range near the NiMn composition at both 700 and 900 °C, detected at a low temperature
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region even in the 50%Ni section. Critical compositions of continuous ordering between C1b and L21 were evaluated from NiMnSb/Ni2MnSb diffusion couples. The obtained results are consistent with the previous data. In the DT quenched at 900 °C, the martensite structure in the B2 or L21 phase region was observed in a certain range to 16 at.% Sb.
Acknowledgments The authors acknowledge support from JSPS KAKENHI grant number JP15H05766.
ACCEPTED MANUSCRIPT References 1
S.A. Wolf, D.D. Awschalom, R.A. Buhrman, J.M. Daughton, S. von Molnar, M.L. Roukes, et al. Science. 294 (2001) 1488-95. Y. Sutou, Y. Imano, N. Koeda, T. Omori, R. Kainuma, K. Ishida, K. Oikawa, Appl. Phys. Lett. 85 (2004) 4358.
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S. Chatterjee, S. Giri, S. Majumdar, SK. De, J Magn Magn Mater. 320 (2008) 617-21.
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Deen, Phil. Mag., 89, (2009) 2093–2109
Intermetallics,
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(2015) 28-41.
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5 M. Nagasako, Y. Taguchi, T. Miyamoto, T. Kanomata, K.R.A. Ziebeck, R. Kainuma,
6 T.B. Massalski, in: T.B. Massalski (Ed.), Binary Alloys Phase Diagrams, second ed., ASM International, 1990, p. 2580 7
C. Guo, X. Du, Intermetallics 13 (2005) 525
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8 T.B. Massalski, in: T.B. Massalski (Ed.), Binary Alloys Phase Diagrams, second ed., ASM International, 1990, p. 2598
9 T.B. Massalski, in: T.B. Massalski (Ed.), Binary Alloys Phase Diagrams, second ed., ASM
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International, 1990, p. 2853
10 P.J. Brown, A.P. Gandy, R. Kainuma, T. Kanomata, T. Miyamoto, M. Nagasako, K.U. Neumann,
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A.Sheikh, K.R.A.Ziebeck,
J. Phys. Cond. Matter., 22 (2010) 206004.
11 T. Miyamoto, M. Nagasako, R. Kainuma, J. Alloys and Comp., 549 (2013) 57–63. 12 J.C. Zhao, in: J.C. Zhao (Ed.), Methods for Phase Diagram Determination, Elsevier, Oxford, 2007, p. 246.
13 R. Ducher, R. Kainuma, I. Ohnuma, K. Ishida, J. Alloys Comp. 437 (2007) 93–101. 14 R. Kainuma, in: J.C. Zhao (Ed.), Methods for Phase Diagram Determination, Elsevier, Oxford, 2007, p.361 15 M. Nagasako and R. Kainuma, unpublished work.
ACCEPTED MANUSCRIPT Captions Fig. 1
A schematic drawing of the bcc-based crystal structure showing the atomic site configurations of the four fcc-sublattices that describe B2 Ni(Mn,Sb), full-Heusler Ni2MnSb, and half-Heusler NiMnSb structures. Binary phase diagrams constituting the Ni-Mn-Sb ternary system. [6-9]
Fig.3
SEM microstructure near the A1 and B2 phases in the Ni/Mn/Sb diffusion triple annealed
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Fig.2
at 900 °C for 3h.
Concentration-penetration profiles for Mn and Sb elements near the diffusion zone in the
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Fig.4
Ni/Mn/Sb diffusion triple annealed at 900 °C for 12h, showing (a) phase decomposition
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and (b) continuous ordering. Equilibrium concentrations were evaluated by extrapolating the profiles to the phase interface as shown in (a) and critical composition of continuous ordering was determined from the singular point (b).
Typical SEM images of two phase alloys annealed at 700 °C for 72h.
Fig.6
Phase equilibria at (a) 700 °C and (b) 900 °C in the Ni-Mn-Sb ternary system, where the
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Fig.5
stoichiometric compositions of NiMnSb and Ni2MnSb are symbolled with open and closed triangles, respectively.
Vertical section diagram for the bcc and martensite phases in the 50 at.% Ni section,
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Fig.7
together with Ms and Curie temperatures in the ordered bcc alloys reported in a previous
Fig.8
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paper [2].
SEM microstructures and concentration-penetration profiles for Mn and Sb elements near
the diffusion zone in the NiMnSb/Ni2MnSb diffusion couples annealed at (a) 600 °C, (b) 700 °C, (c) 800 °C and (d) 900 °C.
Fig.9
Vertical section diagram for Ni2-xMnSb, together with L21/C1b order-disorder transformation and Curie temperature curves reported in a previous paper [5].
Fig.10
(a) SEM microstructure near the martensite and parent (L21) pseudo-interface in the Ni/Ni-75%Mn/Sb diffusion triple annealed at 900 °C for 6 h. (b) Existing region of the
ACCEPTED MANUSCRIPT martensite phase at room temperature represented in the isothermal section of 900 °C. The blue circles correspond to the concentrations determined by EPMA at some points on the martensite / parent pseudo-interface as demonstrated, for example, with a red point in
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(a).
Equilibrium compositions determined from multi-phase alloys annealed at 700 °C for 72 h.
Table2
Equilibrium compositions determined from multi-phase alloys annealed at 900 °C for 30 h.
Table3
Equilibrium compositions determined from Ni/Mn/Sb diffusion triples annealed at 700 °C
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Table 1
for 24 h.
Equilibrium compositions determined from Ni/Mn/Sb diffusion triples annealed at 900 °C
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Table4
for 1, 3 or 12 h.
Critical concentrations of the martensite/parent pseudo-interface determined from the
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Ni/Ni-75%Mn/Sb diffusion triple annealed at 900 °C for 6 h.
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Table5
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Alloy Composition
Phase B
Phase C
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
A / B or A / B / C B2 / C1b
50.7
4.8
42.0
21.3
70
5
67.2
2.7
41.6
29.2
45
10
47.8
6.5
41.5
55
10
53.6
4.4
63.8
40
15
43.1
10.8
41.2
7
24
15.6
7.8
6.6
50
25
40.9
31.4
57.5
33.2
65
25
59.0
32.2
77.4
9.5
Mn2Sb / β-Mn
5
32
8.8
27.8
2.5
41.3
Ni5Sb2 / NiSb
10
40
25.5
29.8
1.4
45.6
L21 / NiSb
15
40
29.5
32.0
2.0
47.6
C1b / NiSb
10
45
32.7
33.0
1.6
49.8
C1b / NiSb
33
48
37.4
35.1
45.6
46.5
16.6
79.6
C1b / MnSb / L
20
60
7.0
51.7
36.9
34.3
12.6
83.3
NiSb / C1b / L
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5
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50
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Mn (at.%) Sb (at.%)
Phase A
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Table 1 Equilibrium compositions determined from multi-phase alloys annealed at 700 ºC for 72 h
γ / C1b B2/ L21
17.5 2.2
41.5
26.4
B2/ γ / C1b
15.0
B2 / L21
25.0
γ / Ni3Sb 75.7
7.5
C1b / Mn2Sb / β-Mn
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Alloy Composition
Phase A
Phase B
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Table 2 Equilibrium compositions determined from multi-phase alloys annealed at 900 ºC for 30 h
Phase C
Sb (at.%)
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
Sb (at.%)
40
5
41.5
12.2
43.4
9.2
B2/ γ
35
10
34.5
12.6
34.0
3.2
L21 / γ
42.5
10.5
41.5
12.2
43.4
9.2
L21 / B2
30
15
29.2
17.8
30.3
4.5
L21 / γ
7
24
7.0
24.7
14.8
7.7
Ni5Sb2 / γ
65
25
58.8
33.0
57.8
24.3
Mn2Sb / β-Mn
45
30
42.7
31.7
52.2
23.8
L21 / β-Mn
5
32
8.6
27.9
2.5
41.4
Ni5Sb2 / NiSb
49
37
56.5
32.9
44.3
31.8
10
45
29.1
31.2
1.2
48.3
33
48
44.9
47.7
36.8
35.4
16.6
79.7
Mn2Sb / L21 / L
20
60
35.7
34.1
6.3
52.7
13.1
79.7
L21 / NiSb / L
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Mn (at.%)
A / B or A / B / C
Mn (at.%)
54.7
22.4
Mn2Sb / L21 / β-Mn L21 / NiSb
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Phase A
Phase B
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Table 3 Equilibrium compositions determined from diffusion triples annealed at 700 ºC for 24 h
A/B
Sb (at.%)
Mn (at.%)
Sb (at.%)
54.9
1.4
62.7
0.4
Β2 / γ
74.6
2.3
78.9
2.1
γ / β-Mn
45.2
4.3
38.9
1.2
Β2 / γ
19.6
7.2
11.3
23.9
γ / Ni3Sb
14.9
8.5
6.4
24.1
γ / Ni3Sb
33.8
15.8
38.3
0.7
L21 / γ
32.7
16.0
35.0
1.4
L21 / γ
17.8
22.3
21.2
5.9
L21 / γ
2.6
27.3
1.8
39.8
Ni5Sb2 / NiSb
41.4
30.5
80.4
2.4
C1b / β-Mn
2.9
41.5
19.9
28.0
NiSb / L21
46.0
48.4
18.5
77.1
MnSb / L
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Mn (at.%)
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3h
Mn (at.%)
Sb (at.%)
Mn (at.%)
53.8
0.9
57.2
53.7
2.2
53.7
2.4
62.2
3.8
72.4
4.0
49.4
17.9
48.2
19.1
Sb (at.%)
A/B Β2 / γ
62.0
1.6
Β2 / γ
61.3
1.5
Β2 / γ
55.7
13.3
γ / β-Mn
89.4
2.2
γ / β-Mn
54.8
13.1
L21 / β-Mn
61.7
2.9
L21 / γ
1.6
89.3
1.1
γ / β-Mn
1.8
46.5
1.0
Β2 / γ
3.3
60.4
1.5
Β2 / γ
7.7
11.2
24.1
γ / Ni5Sb2
6.9
16.6
22.3
γ / Ni5Sb2
19.0
7.1
13.2
22.8
γ / Ni5Sb2
5.6
8.1
2..3
24.1
γ / Ni5Sb2
41.3
16.0
46.4
7.6
L21 / B2
41.8
18.6
47.5
8.0
L21 / B2
78.6 48.4
14.4
AC C
21.3
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0.5
53.0
12h
Phase B
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1h
Phase A
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Annealing time
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Table 4 Equilibrium compositions determined by diffusion triples annealed at 900 ºC
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Table 5 Critical compositions of parent / martensite boundary at room temperature determined from diffusion triple annealed at 900 ºC
Mn (at.%) Sb (at.%) 12.0
36.9
12.2
40.6
12.4
39.4
12.8
41.2
16.5
AC C
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TE D
39.1
TE D
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AC C
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B2-Ni(Mn,Sb): A,C (Ni) B,D (Mn,Sb) L21-Ni2MnSb: A,C (Ni) B (Mn), D (Sb) C1b-NiMnSb: A (Ni), C (Va) B (Mn), D (Sb) Fig. 1
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Fig. 2
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B2 Mn-rich
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Liquid Sb-rich
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M
γ (A1) Ni-rich
Fig. 3
B2
L21
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TE D
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L21
AC C
B2
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Fig. 4
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a) Ni45Mn15Sb40
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b) Ni25Mn70Sb5
NiSb
g
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EP
TE D
C1b
C1b
Fig. 5
(b) Diffusion Couple
EP
L21
AC C
C1b L21
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Diffusion Triple
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Multiphase Alloy
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(a)
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Fig. 6
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Critical comp. of ordering
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Ms [2]
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Equilibrium comp.
TC [2]
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Critical comp. of P/M
Fig. 7
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(b)
TE D
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(a)
EP
C1b
L21
AC C
L21
C1b
Fig. 8
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(d)
L21
EP
L21
AC C
C1b
TE D
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SC
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(c)
Fig. 8
SC
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TE D
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Tt L21/C1b [5]
AC C
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TC [5]
Fig. 9
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(a)
(b)
20mm
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P(L21) phase
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M phase
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Point analyzed by EPMA P/M critical boundary
20
M
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10
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P(L21)
0 20
30
40 50 at.% Mn
60
70
Fig. 10
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Phase B Mn (at.%) Sb (at.%)
5
50.7
4.8
42.0
70
5
67.2
2.7
41.6
45
10
47.8
6.5
41.5
55
10
53.6
4.4
63.8
40
15
43.1
10.8
41.2
7
24
15.6
7.8
50
25
40.9
31.4
65
25
59.0
32.2
5
32
8.8
27.8
10
40
25.5
15
40
10
21.3
A / B or A / B / C B2 / C1b
29.2
g / C1b
17.5
B2/ L21
2.2
41.5
26.4
B2/ g / C1b B2 / L21
6.6
25.0
g / Ni3Sb
57.5
33.2
77.4
9.5
Mn2Sb / b-Mn
2.5
41.3
Ni5Sb2 / NiSb
29.8
1.4
45.6
L21 / NiSb
29.5
32.0
2.0
47.6
C1b / NiSb
45
32.7
33.0
1.6
49.8
C1b / NiSb
33
48
37.4
35.1
45.6
46.5
16.6
79.6
C1b / MnSb / L
20
60
7.0
51.7
36.9
34.3
12.6
83.3
NiSb / C1b / L
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15.0
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50
Phase C Mn (at.%) Sb (at.%)
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Phase A Mn (at.%) Sb (at.%)
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Alloy Composition Mn (at.%) Sb (at.%)
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Table 1 Equilibrium compositions determined from multi-phase alloys annealed at 700 ºC for 72 h
75.7
7.5
C1b / Mn2Sb / b-Mn
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Phase A
Phase B
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Alloy Composition
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Table 2 Equilibrium compositions determined from multi-phase alloys annealed at 900 ºC for 30 h
Mn (at.%) Sb (at.%)
A / B or A / B / C
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
Mn (at.%)
40
5
41.5
12.2
43.4
9.2
B2/ g
35
10
34.5
12.6
34.0
3.2
L21 / g
42.5
10.5
41.5
12.2
43.4
9.2
L21 / B2
30
15
29.2
17.8
30.3
4.5
L21 / g
7
24
7.0
24.7
14.8
7.7
Ni5Sb2 / g
65
25
58.8
33.0
57.8
24.3
Mn2Sb / b-Mn
45
30
42.7
31.7
52.2
23.8
L21 / b-Mn
5
32
8.6
27.9
2.5
41.4
Ni5Sb2 / NiSb
49
37
56.5
32.9
44.3
31.8
10
45
29.1
31.2
1.2
48.3
33
48
44.9
47.7
36.8
35.4
16.6
79.7
Mn2Sb / L21 / L
20
60
35.7
34.1
6.3
52.7
13.1
79.7
L21 / NiSb / L
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Sb (at.%)
Phase C
54.7
22.4
Mn2Sb / L21 / b-Mn L21 / NiSb
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Phase B
Mn (at.%)
Sb (at.%)
Mn (at.%)
54.9
1.4
62.7
74.6
2.3
45.2
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Phase A
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Table 3 Equilibrium compositions determined from diffusion triples annealed at 700 ºC for 24 h
Sb (at.%)
A/B B2 / g
78.9
2.1
g / b-Mn
4.3
38.9
1.2
B2 / g
19.6
7.2
11.3
23.9
g / Ni3Sb
14.9
8.5
6.4
24.1
g / Ni3Sb
33.8
15.8
38.3
0.7
L21 / g
32.7
16.0
35.0
1.4
L21 / g
17.8
22.3
21.2
5.9
L21 / g
2.6
27.3
1.8
39.8
Ni5Sb2 / NiSb
41.4
30.5
80.4
2.4
C1b / b-Mn
2.9
41.5
19.9
28.0
NiSb / L21
46.0
48.4
18.5
77.1
MnSb / L
AC C
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TE D
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0.4
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Table 4 Equilibrium compositions determined by diffusion triples annealed at 900 ºC
3h
A/B
Sb (at.%)
Mn (at.%)
Sb (at.%)
53.8
0.9
57.2
0.5
B2 / g
53.7
2.2
62.0
1.6
B2 / g
53.7
2.4
61.3
1.5
B2 / g
62.2
3.8
55.7
13.3
g / b-Mn
72.4
4.0
89.4
2.2
g / b-Mn
49.4
17.9
54.8
13.1
L21 / b-Mn
48.2
19.1
61.7
2.9
L21 / g
1.6
89.3
1.1
g / b-Mn
1.8
46.5
1.0
B2 / g
3.3
60.4
1.5
B2 / g
7.7
11.2
24.1
g / Ni5Sb2
21.3
6.9
16.6
22.3
g / Ni5Sb2
19.0
7.1
13.2
22.8
g / Ni5Sb2
5.6
8.1
2..3
24.1
g / Ni5Sb2
41.3
16.0
46.4
7.6
L21 / B2
41.8
18.6
47.5
8.0
L21 / B2
78.6 48.4
SC
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AC C
14.4
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Mn (at.%)
53.0
12h
Phase B
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1h
Phase A
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Annealing time
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Table 5 Critical compositions of parent / martensite boundary at room temperature determined from diffusion triple annealed at 900 ºC
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Mn (at.%) Sb (at.%) 39.1 12.0 12.2
40.6
12.4
39.4
12.8
41.2
16.5
AC C
EP
36.9
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Highlights
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(1) Phase diagrams at 700 and 900 ºC in the Ni-Mn-Sb ternary system were experimentally determined. (2) B2+L21 two-phase region was detected at both 700 and 900 ºC. (3) Critical compositions of L21/C1b ordering were determined in Ni2MnSb/NiMnSb section. (4) Existing region of martensite phase at room temperature was estimated by
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diffusion triple.
S0925-8388(18)33263-8
DOI:
10.1016/j.jallcom.2018.09.035
Reference:
JALCOM 47454
To appear in:
Journal of Alloys and Compounds
Received Date: 2 July 2018 Accepted Date: 3 September 2018
Please cite this article as: T. Miyamoto, M. Nagasako, R. Kainuma, Phase equilibria in the Ni-Mn-Sb alloy system, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2018.09.035. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 2018/07/02 For submission to J. Alloys. Compd.
T. Miyamoto1, M. Nagasako2 and R. Kainuma1*
1
Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02
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Aoba, Sendai 980-8579, Japan. 2
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Phase Equilibria in the Ni-Mn-Sb Alloy System
Institute for Materials Research (IMR), Tohoku University, 2-2-1 Katahira, Sendai 980-8577,
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Japan.
Abstract
Phase equilibria and ordered phase regions in the Ni-Mn-Sb system at 700 and 900 °C and the martensite phase region at room temperature were determined mainly by the diffusion triple method.
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It was confirmed that single-phase region of the ordered bcc phases exists in a wide composition range of a central part at both 700 and 900 °C and that the region is divided into two regions of
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half-Heusler C1b and full-Heusler L21 at 700 °C, while the C1b phase is missing at 900 °C. The B2 + L21 phase separation was also confirmed in a certain composition range near Ni-50%Mn, and the
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iso-Ms (= RT) line in the L21 phase region was also estimated to be located from 12 to 16 at.% Sb.
Keywords
Phase diagram; Ni–Mn–Sb; martensitic transformation; magnetic shape memory; order–disorder transition; Heusler alloy
*Corresponding author. Tel.: +81 22 795 7321; fax: +81 22 795 7323. E-mail address: [email protected] (R. Kainuma).
ACCEPTED MANUSCRIPT 1. Introduction In the Ni-Mn-Sb system, there are three kinds of similarly ordered bcc phases, the NiMn phase with the B2 (Pm-3m) structure, the full-Heusler (FH) Ni2MnSb phase with the L21 (Fm-3m) structure, and the half-Heusler (HH) NiMnSb phase with the C1b (F-43m) structure. The
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HH-NiMnSb alloy is a candidate for half-metallic ferromagnets in spintronic devices [1] and the off-stoichiometric FH-Ni2MnSb alloy a ferromagnetic shape memory alloy [2-4]. Figure 1 shows a schematic illustration of the ordered bcc structures comprising four equivalent FCC sublattices: A, B,
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C and D. In the FH-Ni2MnSb structure, the Ni atoms occupy both the A and C sites, and the Mn and Sb atoms enter to the B and D sites, respectively. If the Ni2MnSb alloy has a B2-Ni(Mn,Sb) structure,
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the Mn and Sb atoms randomly occupy both the B and D sites. In the HH-NiMnSb structure, however, the C site, which is one of the Ni sites in the FH structure, is occupied by vacancies and an ordering of vacancies, i.e., the order-disorder transition from the L21 to the C1b, occurs during cooling in the NiMnSb ternary alloy [5]. Although phase equilibria and stability, including the
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order-disorder and martensitic transformations, are important, the ternary phase diagram in the Ni-Mn-Sb system remains unknown.
Figure 2 shows the Ni-Mn [6,7], Mn-Sb [8] and Ni-Sb [9] binary phase diagrams. In the Ni-Mn
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system, a single phase region of γ with disordered fcc: A1 (Fm-3m) structure exists in a wide composition range and a B2-NiMn phase appears in the temperature range 700-1000 °C near the
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stoichiometric composition. However, in the Ni-Sb and Mn-Sb systems, some intermetallic compounds, such as B81-NiSb (P63/mmc), Ni5Sb2 (C121), D0a -Ni3Sb (Pmmn), B81-MnSb (P63/mmc), and C38-Mn2Sb (P4/nmm) exist with a limited solubility. From this information, the NiSb phase region is expected to connect directly to the MnSb phase with the same crystal structure. Recently, the experimental phase diagram in the Ni-Mn-In system was effectively determined by using the diffusion triple (DT) method [10,11], which is a combinatorial technique to effectively estimate the equilibrium compositions [12]. In the present study, the phase equilibria at 700 and 900 °C in the whole region of the Ni-Mn-Sb
ACCEPTED MANUSCRIPT ternary system and the critical compositions of B2 / L21 and L21 / C1b order-disorder transformations are determined by using the DTs, diffusion couples (DCs) and multi-phase alloys. Furthermore, the composition region where the martensite phase exists at room temperature is evaluated.
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2. Experimental procedures 2-1. Multi-phase alloys
In the present study, the obtained DTs covered a composition range limited to the Ni-Mn side in the
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ternary system. Therefore, many alloy samples were prepared as listed in Tables 1 and 2. The samples were induction-melted from pure Ni (99.9%), Mn (99.9%), and Sb (99.5%) and annealed for
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equilibration at 700 °C for 72h and at 900 °C for 30 h in quartz tubes under an argon atmosphere. Microstructural observation was carried out by scanning electron microscopy (SEM) and the equilibrium compositions were determined by electron probe microanalysis (EPMA). 2-2. Diffusion couples and triples
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The DTs ware prepared by the same method as reported in the Ni-Mn-In [11] and Co-Fe-Ga [13] systems with the following three steps [11]:
(1) Ni/Mn and Ni/Ni-75at%Mn DCs, which were joined with induction melting, were
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diffusion-annealed at 1000 °C for 168 h in evacuated quartz tube to obtain a continuous diffusion zone between the Ni and Mn or Ni-75%Mn blocks.
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(2) A 3-mm-diameter cylindrical hole was formed by electric discharge machining near the diffusion zone of the binary DCs and some Sb chips were inserted into the hole. DTs were finally obtained by diffusion-annealing at 700 °C for 24 h and at 900 °C for 1, 3, or 12 h in evacuated quartz tubes. (3) The obtained DTs were cut from a section vertical to the Sb cylinder and chemically analyzed by EPMA along lines parallel to the Ni/Mn interface. The phase equilibria were determined by using the Ni/Mn/Sb DT samples, and the existing region of the martensite phase at room temperature was evaluated by EPMA from microstructures in the
ACCEPTED MANUSCRIPT Ni/Ni-75%Mn/Sb DT. To determine the critical composition of the L21/C1b order-disorder transition, Ni2MnSb/NiMnSb DCs were also prepared by the melting method, in which the Ni2MnSb block laid on a NiMnSb block in the evacuated quartz tube was heated at 1100 °C (over the melting points of both alloys) for a very short duration of approximately 180 s in an electric furnace and the two
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blocks were joined together without intermixing the master alloys, followed by air-cooling. The
then analyzed by EPMA.
3. Results and discussion
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3-1. Isothermal section diagrams of 700 and 900 °C
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obtained DCs were annealed at 600, 700, 800 and 900 °C for 74, 32, 18 and 10 h, respectively, and
Figure 3 shows the SEM image near diffusion zone in the DT specimen annealed at 900 °C for 3 h, where three distinct regions, Ni-rich γ, Mn-rich B2 and Sb-rich liquid (L) phases, are observed on the lower-left, upper-left and right sides, respectively. Moreover, an additional region with a gray
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contrast labeled by Μ is observed. This region has a typical microstructure of martensite phase with a light gray contrast. Equilibrium compositions among those phases were determined using concentration-penetration profiles obtained by EPMA for the DTs annealed at 700 and 900 °C.
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Figure 4(a) and (b) shows typical concentration-penetration profiles for Mn and Sb elements near the diffusion zone in the DT specimen annealed at 900 °C for 12 h. Phase equilibrium concentrations
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were determined by extrapolating the concentration profiles to the phase interface, as demonstrated in Figure 4(a). The results of equilibrium compositions obtained from the DT samples annealed at 700 and 900 °C are listed in Tables 3 and 4, respectively. Because it is difficult to determine three-phase and solid-liquid-phase equilibria using the DT method, alloy samples with multi-phase structure were prepared and analyzed. The typical microstructures obtained from these specimens are shown in Figure 5. Phase equilibrium concentrations were determined from the average EPMA data obtained from at least different five points for each phase. All the results obtained from alloy specimens annealed at 700 and 900 °C are listed in Tables 1 and 2, respectively.
ACCEPTED MANUSCRIPT Figure 6(a) and (b) shows isothermal section diagrams for 700 and 900 °C, respectively, determined by the present study. The phase equilibria determined by the DT method are basically coincident with those by the alloy method. Both the isothermal diagrams for 700 and 900 °C have the same topological constitution in phase equilibria and all the phases, except the L21 (and C1b)
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phase at 700 °C, continue from each binary system. Contrary to expectations, the NiSb phase region does not directly connect to the MnSb phase even though both phases have the same B81 structure. It is important to note that the L21 + B2 two-phase equilibrium exists in the Ni-Mn-Sb system but not
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in the Ni-Mn-In system [11]. The origin of this difference is unknown, but because almost all the tie-lines from the B2 to the L21 or C1b phase are directed to Ni:Mn:Sb=1:1:1 composition, the phase
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separation may be related to the high thermodynamic stability of the C1b (or L21) phase in the NiMnSb composition region. From these results, one can construct a vertical diagram for the 50%Ni section (Figure 7). Interestingly, the L21 + B2 phase separation appears at a low temperature even in this section, although the continuous ordering transformation exists at 900 °C as demonstrated in the
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concentration-penetration profile without any concentration step [14] (Figure 4[b]). The L21 + B2 phase region drastically widens with decreasing Ni composition as expected (Figure 6). We have observed a dual-martensite structure comprising two phases, i.e., the L21 and the B2, with different
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transformation temperatures in 47%Ni alloys [15]. The details of these alloys will be presented in another paper. Another interesting issue is the locations of the L21 and C1b phase regions. As shown
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in Figure 6, both the regions are perfectly unified and it is difficult to distinguish each other from the shape of the single-phase region in the isothermal section diagram. The vertical diagram of the Ni2MnSb/NiMnSb section will be presented in the next section. According to the Ni-Sb binary phase diagram shown in Figure 2 [9], two binary compounds—Ni5Sb2 and Ni3Sb—should independently exist at 700 °C. However, these phases cannot be distinguished at 700 °C in the present study.
3-2. Order-disorder transformation between L21 and C1b
ACCEPTED MANUSCRIPT Order-disorder transformation from the L21 to C1b phase, that is, ordering of vacancies cited in A and C positions of the L21 structure, have recently been investigated by the present authors in Ni2-xMnIn alloys and the order-disorder transformation temperatures Tt L21/C1b have been determined by differential scanning calorimetry (DSC) [5]. Figure 8 shows the SEM images and the
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corresponding concentration profiles of Sb and Ni near the diffusion zone in the Ni2MnSb/NiMnSb diffusion couples annealed at 600 °C (a), 700 °C (b), 800 °C (c) and 900 °C (d). Although they show a left-right symmetry at 900 °C, at other annealing temperatures, the profile shapes lose this
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symmetry and a singular point appears. In general, such a point corresponds to a critical composition of continuous ordering transformation, such as A2/B2 and B2/D03 [14]. In this case, the profile
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gradient in the ordered phase region is always larger than that in the disordered phase, as demonstrated in the B2/L21 ordering shown in Figure 3(b) because of differences in the interdiffusivity of solute elements. From this perspective, it is obvious that the singular point corresponds to critical composition of L21/ C1b ordering transformation. The compositions at the
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singular point are consistent with the order-disorder transformation temperatures evaluated by DSC in our previous paper (Figure 9) [5]. From this result, the C1b phase should exist at 700 °C, but not at 900 °C (Figure 6[a]). Using the gradient of profile and Fick’s first diffusion law, the diffusivity of the
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C1b phase is concluded to be lower than that of the L21 phase. This relationship is very likely because the site occupancy of vacancies in the C1b phase is limited to Sublattice C, unlike that of the
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L21 phase, which appears in Sublattices A and C (Figure 1). This diffusivity tendency is proved also by an obvious difference in mean grain size between the L21 and C1b regions in the SEM images, that is, the mean grain size in the C1b region is clearly smaller than that in the L21 region (Figure 8[a] and [b]).
3-3. Existing region of martensite phase The pseudo-interface between the parent and the martensite phases as shown in Figure 3 corresponds to the region with the martensitic transformation temperature at room temperature.
ACCEPTED MANUSCRIPT Unfortunately, only limited information was extracted from the DTs with the Ni/Mn/Sb combination. A different DT sample fabricated from Ni/Ni-75%Mn/Sb was therefore prepared and examined. Figure 10(a) shows a typical microstructure near the diffusion zone of the DT specimen. The martensite phase region, with a gray contrast and a lamellar morphology, is recognized and the
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pseudo-interface is clearly detected, as indicated with a blue line. The iso-Ms = RT line (here, Ms is martensitic transformation starting temperature) was evaluated by EPMA analysis for the DT sample (Table 5; Figure 10(b)). Figure 7 shows that the Ms in the 50%Ni section estimated from the iso-Ms
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line is near the Ms temperature line reported by Sutou et al. [2]. The accuracy of the iso-Ms = RT line determined by this method may not be very high, but we can easily estimate the composition region
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with the same Ms temperature of 25 °C. The iso-Ms (= RT) line in the L21 phase region was estimated by this DT sample to be located from 12 to 16 at.% Sb (Figure 10[b]).
4. Conclusion
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The phase equilibrium compositions at 700 and 900 °C in the Ni-Mn-Sb system were determined using DTs and multi-phase alloys. It was confirmed that single-phase region of the ordered bcc phases exists in a wide composition range of a central part and that the region is divided into two
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regions of C1b and L21 at 700 °C. However, the B2 + L21 phase separation was confirmed in a wide composition range near the NiMn composition at both 700 and 900 °C, detected at a low temperature
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region even in the 50%Ni section. Critical compositions of continuous ordering between C1b and L21 were evaluated from NiMnSb/Ni2MnSb diffusion couples. The obtained results are consistent with the previous data. In the DT quenched at 900 °C, the martensite structure in the B2 or L21 phase region was observed in a certain range to 16 at.% Sb.
Acknowledgments The authors acknowledge support from JSPS KAKENHI grant number JP15H05766.
ACCEPTED MANUSCRIPT References 1
S.A. Wolf, D.D. Awschalom, R.A. Buhrman, J.M. Daughton, S. von Molnar, M.L. Roukes, et al. Science. 294 (2001) 1488-95. Y. Sutou, Y. Imano, N. Koeda, T. Omori, R. Kainuma, K. Ishida, K. Oikawa, Appl. Phys. Lett. 85 (2004) 4358.
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S. Chatterjee, S. Giri, S. Majumdar, SK. De, J Magn Magn Mater. 320 (2008) 617-21.
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Deen, Phil. Mag., 89, (2009) 2093–2109
Intermetallics,
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(2015) 28-41.
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5 M. Nagasako, Y. Taguchi, T. Miyamoto, T. Kanomata, K.R.A. Ziebeck, R. Kainuma,
6 T.B. Massalski, in: T.B. Massalski (Ed.), Binary Alloys Phase Diagrams, second ed., ASM International, 1990, p. 2580 7
C. Guo, X. Du, Intermetallics 13 (2005) 525
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8 T.B. Massalski, in: T.B. Massalski (Ed.), Binary Alloys Phase Diagrams, second ed., ASM International, 1990, p. 2598
9 T.B. Massalski, in: T.B. Massalski (Ed.), Binary Alloys Phase Diagrams, second ed., ASM
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International, 1990, p. 2853
10 P.J. Brown, A.P. Gandy, R. Kainuma, T. Kanomata, T. Miyamoto, M. Nagasako, K.U. Neumann,
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A.Sheikh, K.R.A.Ziebeck,
J. Phys. Cond. Matter., 22 (2010) 206004.
11 T. Miyamoto, M. Nagasako, R. Kainuma, J. Alloys and Comp., 549 (2013) 57–63. 12 J.C. Zhao, in: J.C. Zhao (Ed.), Methods for Phase Diagram Determination, Elsevier, Oxford, 2007, p. 246.
13 R. Ducher, R. Kainuma, I. Ohnuma, K. Ishida, J. Alloys Comp. 437 (2007) 93–101. 14 R. Kainuma, in: J.C. Zhao (Ed.), Methods for Phase Diagram Determination, Elsevier, Oxford, 2007, p.361 15 M. Nagasako and R. Kainuma, unpublished work.
ACCEPTED MANUSCRIPT Captions Fig. 1
A schematic drawing of the bcc-based crystal structure showing the atomic site configurations of the four fcc-sublattices that describe B2 Ni(Mn,Sb), full-Heusler Ni2MnSb, and half-Heusler NiMnSb structures. Binary phase diagrams constituting the Ni-Mn-Sb ternary system. [6-9]
Fig.3
SEM microstructure near the A1 and B2 phases in the Ni/Mn/Sb diffusion triple annealed
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Fig.2
at 900 °C for 3h.
Concentration-penetration profiles for Mn and Sb elements near the diffusion zone in the
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Fig.4
Ni/Mn/Sb diffusion triple annealed at 900 °C for 12h, showing (a) phase decomposition
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and (b) continuous ordering. Equilibrium concentrations were evaluated by extrapolating the profiles to the phase interface as shown in (a) and critical composition of continuous ordering was determined from the singular point (b).
Typical SEM images of two phase alloys annealed at 700 °C for 72h.
Fig.6
Phase equilibria at (a) 700 °C and (b) 900 °C in the Ni-Mn-Sb ternary system, where the
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Fig.5
stoichiometric compositions of NiMnSb and Ni2MnSb are symbolled with open and closed triangles, respectively.
Vertical section diagram for the bcc and martensite phases in the 50 at.% Ni section,
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Fig.7
together with Ms and Curie temperatures in the ordered bcc alloys reported in a previous
Fig.8
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paper [2].
SEM microstructures and concentration-penetration profiles for Mn and Sb elements near
the diffusion zone in the NiMnSb/Ni2MnSb diffusion couples annealed at (a) 600 °C, (b) 700 °C, (c) 800 °C and (d) 900 °C.
Fig.9
Vertical section diagram for Ni2-xMnSb, together with L21/C1b order-disorder transformation and Curie temperature curves reported in a previous paper [5].
Fig.10
(a) SEM microstructure near the martensite and parent (L21) pseudo-interface in the Ni/Ni-75%Mn/Sb diffusion triple annealed at 900 °C for 6 h. (b) Existing region of the
ACCEPTED MANUSCRIPT martensite phase at room temperature represented in the isothermal section of 900 °C. The blue circles correspond to the concentrations determined by EPMA at some points on the martensite / parent pseudo-interface as demonstrated, for example, with a red point in
RI PT
(a).
Equilibrium compositions determined from multi-phase alloys annealed at 700 °C for 72 h.
Table2
Equilibrium compositions determined from multi-phase alloys annealed at 900 °C for 30 h.
Table3
Equilibrium compositions determined from Ni/Mn/Sb diffusion triples annealed at 700 °C
SC
Table 1
for 24 h.
Equilibrium compositions determined from Ni/Mn/Sb diffusion triples annealed at 900 °C
M AN U
Table4
for 1, 3 or 12 h.
Critical concentrations of the martensite/parent pseudo-interface determined from the
EP
TE D
Ni/Ni-75%Mn/Sb diffusion triple annealed at 900 °C for 6 h.
AC C
Table5
ACCEPTED MANUSCRIPT
Alloy Composition
Phase B
Phase C
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
A / B or A / B / C B2 / C1b
50.7
4.8
42.0
21.3
70
5
67.2
2.7
41.6
29.2
45
10
47.8
6.5
41.5
55
10
53.6
4.4
63.8
40
15
43.1
10.8
41.2
7
24
15.6
7.8
6.6
50
25
40.9
31.4
57.5
33.2
65
25
59.0
32.2
77.4
9.5
Mn2Sb / β-Mn
5
32
8.8
27.8
2.5
41.3
Ni5Sb2 / NiSb
10
40
25.5
29.8
1.4
45.6
L21 / NiSb
15
40
29.5
32.0
2.0
47.6
C1b / NiSb
10
45
32.7
33.0
1.6
49.8
C1b / NiSb
33
48
37.4
35.1
45.6
46.5
16.6
79.6
C1b / MnSb / L
20
60
7.0
51.7
36.9
34.3
12.6
83.3
NiSb / C1b / L
AC C
M AN U
SC
5
EP
50
TE D
Mn (at.%) Sb (at.%)
Phase A
RI PT
Table 1 Equilibrium compositions determined from multi-phase alloys annealed at 700 ºC for 72 h
γ / C1b B2/ L21
17.5 2.2
41.5
26.4
B2/ γ / C1b
15.0
B2 / L21
25.0
γ / Ni3Sb 75.7
7.5
C1b / Mn2Sb / β-Mn
ACCEPTED MANUSCRIPT
Alloy Composition
Phase A
Phase B
RI PT
Table 2 Equilibrium compositions determined from multi-phase alloys annealed at 900 ºC for 30 h
Phase C
Sb (at.%)
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
Sb (at.%)
40
5
41.5
12.2
43.4
9.2
B2/ γ
35
10
34.5
12.6
34.0
3.2
L21 / γ
42.5
10.5
41.5
12.2
43.4
9.2
L21 / B2
30
15
29.2
17.8
30.3
4.5
L21 / γ
7
24
7.0
24.7
14.8
7.7
Ni5Sb2 / γ
65
25
58.8
33.0
57.8
24.3
Mn2Sb / β-Mn
45
30
42.7
31.7
52.2
23.8
L21 / β-Mn
5
32
8.6
27.9
2.5
41.4
Ni5Sb2 / NiSb
49
37
56.5
32.9
44.3
31.8
10
45
29.1
31.2
1.2
48.3
33
48
44.9
47.7
36.8
35.4
16.6
79.7
Mn2Sb / L21 / L
20
60
35.7
34.1
6.3
52.7
13.1
79.7
L21 / NiSb / L
AC C
EP
TE D
M AN U
SC
Mn (at.%)
A / B or A / B / C
Mn (at.%)
54.7
22.4
Mn2Sb / L21 / β-Mn L21 / NiSb
ACCEPTED MANUSCRIPT
Phase A
Phase B
RI PT
Table 3 Equilibrium compositions determined from diffusion triples annealed at 700 ºC for 24 h
A/B
Sb (at.%)
Mn (at.%)
Sb (at.%)
54.9
1.4
62.7
0.4
Β2 / γ
74.6
2.3
78.9
2.1
γ / β-Mn
45.2
4.3
38.9
1.2
Β2 / γ
19.6
7.2
11.3
23.9
γ / Ni3Sb
14.9
8.5
6.4
24.1
γ / Ni3Sb
33.8
15.8
38.3
0.7
L21 / γ
32.7
16.0
35.0
1.4
L21 / γ
17.8
22.3
21.2
5.9
L21 / γ
2.6
27.3
1.8
39.8
Ni5Sb2 / NiSb
41.4
30.5
80.4
2.4
C1b / β-Mn
2.9
41.5
19.9
28.0
NiSb / L21
46.0
48.4
18.5
77.1
MnSb / L
AC C
EP
TE D
M AN U
SC
Mn (at.%)
ACCEPTED MANUSCRIPT
3h
Mn (at.%)
Sb (at.%)
Mn (at.%)
53.8
0.9
57.2
53.7
2.2
53.7
2.4
62.2
3.8
72.4
4.0
49.4
17.9
48.2
19.1
Sb (at.%)
A/B Β2 / γ
62.0
1.6
Β2 / γ
61.3
1.5
Β2 / γ
55.7
13.3
γ / β-Mn
89.4
2.2
γ / β-Mn
54.8
13.1
L21 / β-Mn
61.7
2.9
L21 / γ
1.6
89.3
1.1
γ / β-Mn
1.8
46.5
1.0
Β2 / γ
3.3
60.4
1.5
Β2 / γ
7.7
11.2
24.1
γ / Ni5Sb2
6.9
16.6
22.3
γ / Ni5Sb2
19.0
7.1
13.2
22.8
γ / Ni5Sb2
5.6
8.1
2..3
24.1
γ / Ni5Sb2
41.3
16.0
46.4
7.6
L21 / B2
41.8
18.6
47.5
8.0
L21 / B2
78.6 48.4
14.4
AC C
21.3
M AN U
SC
0.5
53.0
12h
Phase B
TE D
1h
Phase A
EP
Annealing time
RI PT
Table 4 Equilibrium compositions determined by diffusion triples annealed at 900 ºC
RI PT
ACCEPTED MANUSCRIPT
M AN U
SC
Table 5 Critical compositions of parent / martensite boundary at room temperature determined from diffusion triple annealed at 900 ºC
Mn (at.%) Sb (at.%) 12.0
36.9
12.2
40.6
12.4
39.4
12.8
41.2
16.5
AC C
EP
TE D
39.1
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
B2-Ni(Mn,Sb): A,C (Ni) B,D (Mn,Sb) L21-Ni2MnSb: A,C (Ni) B (Mn), D (Sb) C1b-NiMnSb: A (Ni), C (Va) B (Mn), D (Sb) Fig. 1
AC C
EP
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Fig. 2
RI PT
ACCEPTED MANUSCRIPT
M AN U
B2 Mn-rich
SC
Liquid Sb-rich
AC C
EP
TE D
M
γ (A1) Ni-rich
Fig. 3
B2
L21
EP
TE D
M AN U
SC
L21
AC C
B2
RI PT
ACCEPTED MANUSCRIPT
Fig. 4
RI PT
ACCEPTED MANUSCRIPT
a) Ni45Mn15Sb40
M AN U
SC
b) Ni25Mn70Sb5
NiSb
g
AC C
EP
TE D
C1b
C1b
Fig. 5
(b) Diffusion Couple
EP
L21
AC C
C1b L21
TE D
Diffusion Triple
M AN U
Multiphase Alloy
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
Fig. 6
RI PT
ACCEPTED MANUSCRIPT
Critical comp. of ordering
TE D
Ms [2]
M AN U
SC
Equilibrium comp.
TC [2]
AC C
EP
Critical comp. of P/M
Fig. 7
ACCEPTED MANUSCRIPT
(b)
TE D
M AN U
SC
RI PT
(a)
EP
C1b
L21
AC C
L21
C1b
Fig. 8
ACCEPTED MANUSCRIPT
(d)
L21
EP
L21
AC C
C1b
TE D
M AN U
SC
RI PT
(c)
Fig. 8
SC
RI PT
ACCEPTED MANUSCRIPT
TE D
M AN U
Tt L21/C1b [5]
AC C
EP
TC [5]
Fig. 9
ACCEPTED MANUSCRIPT
(a)
(b)
20mm
TE D
M AN U
P(L21) phase
SC
M phase
RI PT
Point analyzed by EPMA P/M critical boundary
20
M
AC C
10
EP
P(L21)
0 20
30
40 50 at.% Mn
60
70
Fig. 10
ACCEPTED MANUSCRIPT
Phase B Mn (at.%) Sb (at.%)
5
50.7
4.8
42.0
70
5
67.2
2.7
41.6
45
10
47.8
6.5
41.5
55
10
53.6
4.4
63.8
40
15
43.1
10.8
41.2
7
24
15.6
7.8
50
25
40.9
31.4
65
25
59.0
32.2
5
32
8.8
27.8
10
40
25.5
15
40
10
21.3
A / B or A / B / C B2 / C1b
29.2
g / C1b
17.5
B2/ L21
2.2
41.5
26.4
B2/ g / C1b B2 / L21
6.6
25.0
g / Ni3Sb
57.5
33.2
77.4
9.5
Mn2Sb / b-Mn
2.5
41.3
Ni5Sb2 / NiSb
29.8
1.4
45.6
L21 / NiSb
29.5
32.0
2.0
47.6
C1b / NiSb
45
32.7
33.0
1.6
49.8
C1b / NiSb
33
48
37.4
35.1
45.6
46.5
16.6
79.6
C1b / MnSb / L
20
60
7.0
51.7
36.9
34.3
12.6
83.3
NiSb / C1b / L
AC C
TE D
15.0
EP
50
Phase C Mn (at.%) Sb (at.%)
SC
Phase A Mn (at.%) Sb (at.%)
M AN U
Alloy Composition Mn (at.%) Sb (at.%)
RI PT
Table 1 Equilibrium compositions determined from multi-phase alloys annealed at 700 ºC for 72 h
75.7
7.5
C1b / Mn2Sb / b-Mn
ACCEPTED MANUSCRIPT
Phase A
Phase B
SC
Alloy Composition
RI PT
Table 2 Equilibrium compositions determined from multi-phase alloys annealed at 900 ºC for 30 h
Mn (at.%) Sb (at.%)
A / B or A / B / C
Mn (at.%)
Sb (at.%)
Mn (at.%)
Sb (at.%)
Mn (at.%)
40
5
41.5
12.2
43.4
9.2
B2/ g
35
10
34.5
12.6
34.0
3.2
L21 / g
42.5
10.5
41.5
12.2
43.4
9.2
L21 / B2
30
15
29.2
17.8
30.3
4.5
L21 / g
7
24
7.0
24.7
14.8
7.7
Ni5Sb2 / g
65
25
58.8
33.0
57.8
24.3
Mn2Sb / b-Mn
45
30
42.7
31.7
52.2
23.8
L21 / b-Mn
5
32
8.6
27.9
2.5
41.4
Ni5Sb2 / NiSb
49
37
56.5
32.9
44.3
31.8
10
45
29.1
31.2
1.2
48.3
33
48
44.9
47.7
36.8
35.4
16.6
79.7
Mn2Sb / L21 / L
20
60
35.7
34.1
6.3
52.7
13.1
79.7
L21 / NiSb / L
AC C
EP
TE D
M AN U
Sb (at.%)
Phase C
54.7
22.4
Mn2Sb / L21 / b-Mn L21 / NiSb
ACCEPTED MANUSCRIPT
Phase B
Mn (at.%)
Sb (at.%)
Mn (at.%)
54.9
1.4
62.7
74.6
2.3
45.2
SC
Phase A
RI PT
Table 3 Equilibrium compositions determined from diffusion triples annealed at 700 ºC for 24 h
Sb (at.%)
A/B B2 / g
78.9
2.1
g / b-Mn
4.3
38.9
1.2
B2 / g
19.6
7.2
11.3
23.9
g / Ni3Sb
14.9
8.5
6.4
24.1
g / Ni3Sb
33.8
15.8
38.3
0.7
L21 / g
32.7
16.0
35.0
1.4
L21 / g
17.8
22.3
21.2
5.9
L21 / g
2.6
27.3
1.8
39.8
Ni5Sb2 / NiSb
41.4
30.5
80.4
2.4
C1b / b-Mn
2.9
41.5
19.9
28.0
NiSb / L21
46.0
48.4
18.5
77.1
MnSb / L
AC C
EP
TE D
M AN U
0.4
ACCEPTED MANUSCRIPT
Table 4 Equilibrium compositions determined by diffusion triples annealed at 900 ºC
3h
A/B
Sb (at.%)
Mn (at.%)
Sb (at.%)
53.8
0.9
57.2
0.5
B2 / g
53.7
2.2
62.0
1.6
B2 / g
53.7
2.4
61.3
1.5
B2 / g
62.2
3.8
55.7
13.3
g / b-Mn
72.4
4.0
89.4
2.2
g / b-Mn
49.4
17.9
54.8
13.1
L21 / b-Mn
48.2
19.1
61.7
2.9
L21 / g
1.6
89.3
1.1
g / b-Mn
1.8
46.5
1.0
B2 / g
3.3
60.4
1.5
B2 / g
7.7
11.2
24.1
g / Ni5Sb2
21.3
6.9
16.6
22.3
g / Ni5Sb2
19.0
7.1
13.2
22.8
g / Ni5Sb2
5.6
8.1
2..3
24.1
g / Ni5Sb2
41.3
16.0
46.4
7.6
L21 / B2
41.8
18.6
47.5
8.0
L21 / B2
78.6 48.4
SC
M AN U
AC C
14.4
RI PT
Mn (at.%)
53.0
12h
Phase B
TE D
1h
Phase A
EP
Annealing time
RI PT
ACCEPTED MANUSCRIPT
M AN U
SC
Table 5 Critical compositions of parent / martensite boundary at room temperature determined from diffusion triple annealed at 900 ºC
TE D
Mn (at.%) Sb (at.%) 39.1 12.0 12.2
40.6
12.4
39.4
12.8
41.2
16.5
AC C
EP
36.9
ACCEPTED MANUSCRIPT
Highlights
RI PT
(1) Phase diagrams at 700 and 900 ºC in the Ni-Mn-Sb ternary system were experimentally determined. (2) B2+L21 two-phase region was detected at both 700 and 900 ºC. (3) Critical compositions of L21/C1b ordering were determined in Ni2MnSb/NiMnSb section. (4) Existing region of martensite phase at room temperature was estimated by
AC C
EP
TE D
M AN U
SC
diffusion triple.