- Email: [email protected]
Crystallization behavior of low temperature pre-annealed Zr46.8Ti8.2Ni10Cu7.5Be27.5—bulk glass
Materials Science and Engineering A 375–377 (2004) 355–358
Crystallization behavior of low temperature pre-annealed Zr46.8Ti8.2 Ni10 Cu7.5Be27.5—bulk glass S. Mechler∗ , N. Wanderka, M.-P. Macht Hahn-Meitner-Institute Berlin, Glienicker Street 100, D-14109 Berlin, Germany
Abstract During heat treatment of metallic bulk glasses at temperatures below the calorimetric glass transition temperature Tg , the glasses undergo microstructural alterations indicated by their thermal behavior as observed by DSC, but not discernible by X-ray diffraction (XRD). A reversible enthalpy recovery at Tg indicates a slow, reversible relaxation of the glass into a temperature dependent structural equilibrium state. After prolonged annealing times below Tg the crystallization is irreversibly affected, i.e. it starts at a lower temperature, takes a different pathway and ends up in a different crystalline microstructure. This behavior was studied in Zr46.8 Ti8.2 Ni10 Cu7.5 Be27.5 —bulk glass (V4) after preceding long term annealing well below Tg = 603 K by means of differential scanning calorimeter (DSC), XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and microhardness measurements. © 2003 Elsevier B.V. All rights reserved. Keywords: Metallic bulk glass; ZrTiNiCuBe bulk glass; Decomposition and crystallization; Quasicrystals; Isothermal; Low temperature annealing
1. Introduction The Zr46.8 Ti8.2 Ni10 Cu7.5 Be27.5 —bulk glass (V4) is one of the most stable metallic bulk glasses [1]. The stability is linked to the nature and nucleation kinetics of the crystalline phases which form during heat treatment of the glass. Several studies about the crystallization of Zr–Ti–Cu–Ni–Be alloys have been performed during the last few years [2–12]: the equilibrium phases have been identified [8–10] and the decomposition and crystallization behavior of ZrTiCuNiBe glasses have been investigated [2–12]. A general feature of ZrTiCuNiBe glasses is their strong tendency for decomposition. This leads to crystallization of intermetallic phases like e.g. modified Be2 Zr and Zr2 Cu [8,10] consisting of a composition far away from that of the multicomponent alloy. Depending on the thermal history, the crystallization of ZrTiCuNiBe glasses follows different pathways, which end up in different crystalline microstructures [8,12]. Recently, the formation of icosahedral quasicrystals in the glass V4 at temperatures above the glass transition was reported, which was correlated to the decomposition of the glass [11,12]. Furthermore, small reversible enthalpy recovery effects in the V4 glass have been found by calorimetric analysis af∗
Corresponding author. E-mail address: [email protected] (S. Mechler).
0921-5093/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2003.10.128
ter long time annealing well below the glass transition [13], which may have been caused by reversible and temperature dependent microstructural changes in the glass. The present paper reports about the microstructure of the V4 glass after long time annealing at temperatures well below Tg and how this pre-annealing effects the pathway of subsequent crystallization.
2. Experimental V4 bulk samples were prepared appropriate for the respective experiments from rapidly cooled ingots. The production of the V4 glass ingots is described elsewhere [11]. The material was characterized by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM) to ascertain the absence of undesirable primary crystals [2]. The thermal behavior of the glass between 473 and 873 K was studied by caloric measurements in a Perkin-Elmer—Pyris 1 differential scanning calorimeter (DSC) at a heating rate of 4 K/min. Isothermal annealing at 573 K (±1.5 K) up to 12 weeks were performed in a tube furnace under vacuum of 10−4 Pa. To study the resulting behavior of subsequent crystallization, heating experiments were performed. The heating was carried out in the DSC apparatus with a heating rate of 4 K/min.
356
S. Mechler et al. / Materials Science and Engineering A 375–377 (2004) 355–358
After reaching different maximum temperatures the samples were immediately cooled (≈200 K/min) to room temperature. The heat release during these annealing procedures was recorded. After all heat treatments the samples were analyzed by XRD, transmission electron microscopy (TEM), SEM, DSC and microhardness measurements. The XRD spectra were measured using Cu K␣ radiation in the θ–2θ configuration. The microstructure of selected samples was characterized by high-resolution TEM (HRTEM) linked with nanobeam electron diffraction in a Philips CM 30 microscope operated at 300 kV. The sample preparation of the TEM specimens is described elsewhere [11]. All specimens were analyzed by SEM (Philips XL 30 ESEM) at 20–30 kV in the backscattered electron (BSE) mode.
3. Results Fig. 1 shows DSC scans of an as-quenched sample and a sample pre-annealed for 42 days at 573 K. It can be seen that pre-annealing leads to a different thermal behavior during heating in the DSC. The pre-annealed sample shows an endothermic heat recovery in the glass transition region that can be interpreted to be caused from structural changes [14]. This endothermic heat recovery has reached a saturation value after the first 3–4 days of pre-annealing. For the pre-annealed glass, the first crystallization peak shifts to lower temperatures; the onset of crystallization Tx decreases from 729 K for the as-quenched sample to about 711 K, while the heat of crystallization increases from 72 to 89 J/g. The crystallization peaks at higher temperatures are almost vanished in the DSC scan after the pre-annealing. However, the overall heat release by crystallization during heating up to 873 K remains almost the same as for the as-quenched glass.
Fig. 1. DSC scans of the V4 bulk glass after pre-annealing for different times (d = days) at 573 K, as indicated in the figure. The effect of pre-annealing on the thermal behavior is shown.
The inset in Fig. 1 depicts the evolution of the shift of the first crystallization peak with time during pre-annealing at 573 K. With increasing annealing time, the characteristic temperatures of the main crystallization peak shift to lower temperatures. For annealing times greater than 7 days, a small crystallization peak is developing on the front slope of the main crystallization peak. This additional peak is getting larger with increasing annealing time, while the main crystallization peak becomes broader. After an annealing time of 15 days both peaks are of equal size and for annealing times longer than 28 days they can not be distinguished anymore. Annealing up to 42 days at 573 K does not result in further great changes in the thermal behavior. In the following we focus on the crystallization behavior of the V4 glass after pre-annealing for 42 days at 573 K. Fig. 2 shows XRD spectra of the glass, taken after pre-annealing for 42 days at 573 K in the pre-annealed state (state a, spectrum a); and after subsequent crystallization by heating in the DSC up to 713.5 K, according to 15% (state b, spectrum b); to 716.3 K, according to 40% (state c, spectrum c); and to 733.2 K, according to 100% (state d, spectrum d) of the heat release of the main crystallization peak in the DSC spectrum. Each of the shown spectra represents a certain state (a–d) in the pathway of crystallization. As a reference, one spectrum is taken after partial crystallization of the as-quenched glass up to 100% of the heat release of the main crystallization peak (state e, spectrum e). The XRD spectra taken after only pre-annealing (state a) does not differ from the diffuse scattering spectrum typical for the as-quenched state. Even prolonged annealing of the glass for 12 weeks (84 days) at 573 K (not shown
Fig. 2. XRD spectra of V4 glass taken after different heat treatments. (a) Pre-annealed for 42 days at 573 K, (b)–(d): pre-annealed for 42 days at 573 K and subsequently heated in the DSC with a heating rate of 4 K/min up to (b) 713.5 K, (c) 716.3 K, (d) 733.2 K, and (e) heated in the DSC from the as-quenched state up to 745 K. Indication of Bragg peaks: “o”, QX2 ; “+”, X1 .
S. Mechler et al. / Materials Science and Engineering A 375–377 (2004) 355–358
Fig. 3. TEM image of the decomposed V4 glass after annealing for 42 days at 573 K and the corresponding electron diffraction pattern.
in the figure) does not lead to any change in the XRD spectrum. After heating the pre-annealed glass up to 713.5 K (state b) several Bragg peaks superimposed on the diffuse spectrum of the amorphous phase can be seen in the XRD spectrum. These Bragg peaks correspond to a quasicrystalline phase (QX2 ), as will be shown later. They are narrow, indicating a rather coarse grained microstructure. After heating the annealed glass up to 716.3 K (state c) the Bragg peaks have become larger, indicating further growth of the quasicrystalline phase. Additional Bragg peaks of at least one further crystalline phase can be detected in the spectrum after heating the pre-annealed glass up to 733.2 K (state d). The microstructure mainly consists of one crystalline phase X1 (indicated as “+” in the figure) and the quasicrystalline phase QX2 (indicated as “o” in the figure). The XRD spectrum of the sample, heated from the as-quenched state up to 745 K (state e) shows Bragg peaks of the phase X1 , only small amounts of further crystalline phases are present. No Bragg peaks of the quasicrystalline phase are discernible. Only when heated up to 873 K, new phases (e.g. modified Be2 Zr and a Zr2 Cu like phase) appear in the microstructure. TEM analysis of the as-quenched glass reveals a completely homogeneous amorphous phase, whereas bright spots in the corresponding TEM image of the pre-annealed sample (state a) indicate inhomogeneities (Fig. 3). The bright regions, with a typical size of about 30–40 nm, are surrounded by a darker border. The electron diffraction pattern, which does not show any Bragg spots, indicates the amorphous nature of the pre-annealed material (see also XRD spectrum a in Fig. 2). The decomposition of the glass was also established by analysis with the three dimensional atom probe. The microhardness of the as-quenched glass of about 5.7 GPa remains unchanged after pre-annealing for even 12 weeks, whereas already partial crystallization increases the microhardness significantly. The TEM image (Fig. 4) of a sample heated up to 709 K, according to 4% of the heat release of the main crystallization peak in the DSC spectrum shows dark polygons with a typical size of about
357
Fig. 4. TEM image of the decomposed and partially crystallized V4 glass after annealing for 42 days at 573 K and subsequent heating in the DSC with a heating rate of 4 K/min up to 709 K.
40–250 nm embedded in the decomposed amorphous matrix. It is noted, that the bright regions, which could be seen in Fig. 3 have become larger. After heating the pre-annealed sample up to 733.2 K (state d), the bright regions are grown up to 800 nm in diameter, as was observed by SEM (not shown here). Fig. 5 shows a HRTEM image of one polygon. The corresponding diffraction pattern shows a five-fold symmetry, which is typical for a quasicrystalline phase. The lattice fringe distances in the direction of the different axis of the lattice show that these quasicrystals are not of the same type as the quasicrystals QX1 , which develop during annealing the V4 glass at 643 K (i.e. above Tg ) as a first stage phase [12]. In contrast to the transient quasicrystalline phase QX1 , the phase QX2 seems to be rather stable. After an annealing for 3 h at 693 K of the pre-annealed glass the Bragg peaks of the QX2 phase are still present in a XRD spectrum (not shown here) where they had grown during the first hour of annealing. Future analysis will clear the structure type of this quasicrystalline phase.
Fig. 5. HRTEM image with the five-fold zone axis of a quasicrystal, which has formed during heating in the DSC (4 K/min) up to 709 K after pre-annealing for 42 days at 573 K and the corresponding nanobeam electron diffraction pattern.
358
S. Mechler et al. / Materials Science and Engineering A 375–377 (2004) 355–358
4. Conclusions During long time annealing of the V4 alloy at temperatures well below Tg not only reversible microstructural alterations do occur. For prolonged times, decomposition into two amorphous phases takes place, leading to the formation of a rather stable quasicrystalline phase during heating of the pre-annealed alloy. The structure of this phase and the microstructure of the crystallized glass differs significantly from that quasicrystalline phase, which develops during crystallization of an as-quenched glass, thus indicating the strong effect of the thermal history on the crystallization behavior of the glass.
[3] [4] [5] [6] [7] [8] [9] [10]
References
[11] [12]
[1] W.L. Johnson, Mater. Sci. Forum 225–227 (1996) 35–50; W.L. Johnson, MRS Bull. 24 (1999) 2–56. [2] M.-P. Macht, N. Wanderka, A. Wiedenmann, H. Wollenberger, Q. Wei, S.G. Klose, A. Sagel, H.J. Fecht, in: Proceedings of the MRS
[13] [14]
Symposium, vol. 398, MRS, Pittsburgh, PA, USA, 1996, pp. 375– 380. A. Wiedenmann, J.-M. Liu, Solid State Commun. 100 (1996) 331– 335. S. Schneider, U. Geyer, P. Thiyagarajan, W.L. Johnson, Mater. Sci. Forum 235–238 (1997) 337–342. H. Herrmann, A. Wiedemann, P. Uebele, J. Phys.: Condens. Matter 9 (1997) L509–L515. J.F. Loeffler, P. Thiyagarajan, W.L. Johnson, J. Appl. Crystallogr. 33 (2000) 500. T.A. Waniuk, J. Schroers, W.L. Johnson, Appl. Phys. Lett. 78 (2001) 1213–1215. Q. Wei, N. Wanderka, P. Schubert-Bischoff, M.-P. Macht, S. Friedrich, J. Mater. Res. 15 (8) (2000) 1729–1734. J. Schroers, R. Busch, A. Masuhr, W.L. Johnson, Appl. Phys. Lett. 74 (1999) 2806–2808. M.-P. Macht, Q. Wei, N. Wanderka, I. Sieber, N. Deyneka, Mater. Sci. Forum 343–346 (2000) 173–178. N. Wanderka, M.-P. Macht, M. Seidel, S. Mechler, K. Stahl, J.Z. Jiang, Appl. Phys. Lett. 77 (2000) 3935–3937. M.-P. Macht, S. Mechler, M. Mueller, N. Wanderka, Mater. Sci. Forum 386–388 (2002) 99–104. T. Zumkley, V. Naundorf, M.-P. Macht, G. Frohberg, Mater. Sci. Forum 386–388 (2002) 65–70. R. Bruening, J.O. Stroem-Olsen, Phys. Rev. B 41 (1990) 2678–2683.
Crystallization behavior of low temperature pre-annealed Zr46.8Ti8.2 Ni10 Cu7.5Be27.5—bulk glass S. Mechler∗ , N. Wanderka, M.-P. Macht Hahn-Meitner-Institute Berlin, Glienicker Street 100, D-14109 Berlin, Germany
Abstract During heat treatment of metallic bulk glasses at temperatures below the calorimetric glass transition temperature Tg , the glasses undergo microstructural alterations indicated by their thermal behavior as observed by DSC, but not discernible by X-ray diffraction (XRD). A reversible enthalpy recovery at Tg indicates a slow, reversible relaxation of the glass into a temperature dependent structural equilibrium state. After prolonged annealing times below Tg the crystallization is irreversibly affected, i.e. it starts at a lower temperature, takes a different pathway and ends up in a different crystalline microstructure. This behavior was studied in Zr46.8 Ti8.2 Ni10 Cu7.5 Be27.5 —bulk glass (V4) after preceding long term annealing well below Tg = 603 K by means of differential scanning calorimeter (DSC), XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and microhardness measurements. © 2003 Elsevier B.V. All rights reserved. Keywords: Metallic bulk glass; ZrTiNiCuBe bulk glass; Decomposition and crystallization; Quasicrystals; Isothermal; Low temperature annealing
1. Introduction The Zr46.8 Ti8.2 Ni10 Cu7.5 Be27.5 —bulk glass (V4) is one of the most stable metallic bulk glasses [1]. The stability is linked to the nature and nucleation kinetics of the crystalline phases which form during heat treatment of the glass. Several studies about the crystallization of Zr–Ti–Cu–Ni–Be alloys have been performed during the last few years [2–12]: the equilibrium phases have been identified [8–10] and the decomposition and crystallization behavior of ZrTiCuNiBe glasses have been investigated [2–12]. A general feature of ZrTiCuNiBe glasses is their strong tendency for decomposition. This leads to crystallization of intermetallic phases like e.g. modified Be2 Zr and Zr2 Cu [8,10] consisting of a composition far away from that of the multicomponent alloy. Depending on the thermal history, the crystallization of ZrTiCuNiBe glasses follows different pathways, which end up in different crystalline microstructures [8,12]. Recently, the formation of icosahedral quasicrystals in the glass V4 at temperatures above the glass transition was reported, which was correlated to the decomposition of the glass [11,12]. Furthermore, small reversible enthalpy recovery effects in the V4 glass have been found by calorimetric analysis af∗
Corresponding author. E-mail address: [email protected] (S. Mechler).
0921-5093/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2003.10.128
ter long time annealing well below the glass transition [13], which may have been caused by reversible and temperature dependent microstructural changes in the glass. The present paper reports about the microstructure of the V4 glass after long time annealing at temperatures well below Tg and how this pre-annealing effects the pathway of subsequent crystallization.
2. Experimental V4 bulk samples were prepared appropriate for the respective experiments from rapidly cooled ingots. The production of the V4 glass ingots is described elsewhere [11]. The material was characterized by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM) to ascertain the absence of undesirable primary crystals [2]. The thermal behavior of the glass between 473 and 873 K was studied by caloric measurements in a Perkin-Elmer—Pyris 1 differential scanning calorimeter (DSC) at a heating rate of 4 K/min. Isothermal annealing at 573 K (±1.5 K) up to 12 weeks were performed in a tube furnace under vacuum of 10−4 Pa. To study the resulting behavior of subsequent crystallization, heating experiments were performed. The heating was carried out in the DSC apparatus with a heating rate of 4 K/min.
356
S. Mechler et al. / Materials Science and Engineering A 375–377 (2004) 355–358
After reaching different maximum temperatures the samples were immediately cooled (≈200 K/min) to room temperature. The heat release during these annealing procedures was recorded. After all heat treatments the samples were analyzed by XRD, transmission electron microscopy (TEM), SEM, DSC and microhardness measurements. The XRD spectra were measured using Cu K␣ radiation in the θ–2θ configuration. The microstructure of selected samples was characterized by high-resolution TEM (HRTEM) linked with nanobeam electron diffraction in a Philips CM 30 microscope operated at 300 kV. The sample preparation of the TEM specimens is described elsewhere [11]. All specimens were analyzed by SEM (Philips XL 30 ESEM) at 20–30 kV in the backscattered electron (BSE) mode.
3. Results Fig. 1 shows DSC scans of an as-quenched sample and a sample pre-annealed for 42 days at 573 K. It can be seen that pre-annealing leads to a different thermal behavior during heating in the DSC. The pre-annealed sample shows an endothermic heat recovery in the glass transition region that can be interpreted to be caused from structural changes [14]. This endothermic heat recovery has reached a saturation value after the first 3–4 days of pre-annealing. For the pre-annealed glass, the first crystallization peak shifts to lower temperatures; the onset of crystallization Tx decreases from 729 K for the as-quenched sample to about 711 K, while the heat of crystallization increases from 72 to 89 J/g. The crystallization peaks at higher temperatures are almost vanished in the DSC scan after the pre-annealing. However, the overall heat release by crystallization during heating up to 873 K remains almost the same as for the as-quenched glass.
Fig. 1. DSC scans of the V4 bulk glass after pre-annealing for different times (d = days) at 573 K, as indicated in the figure. The effect of pre-annealing on the thermal behavior is shown.
The inset in Fig. 1 depicts the evolution of the shift of the first crystallization peak with time during pre-annealing at 573 K. With increasing annealing time, the characteristic temperatures of the main crystallization peak shift to lower temperatures. For annealing times greater than 7 days, a small crystallization peak is developing on the front slope of the main crystallization peak. This additional peak is getting larger with increasing annealing time, while the main crystallization peak becomes broader. After an annealing time of 15 days both peaks are of equal size and for annealing times longer than 28 days they can not be distinguished anymore. Annealing up to 42 days at 573 K does not result in further great changes in the thermal behavior. In the following we focus on the crystallization behavior of the V4 glass after pre-annealing for 42 days at 573 K. Fig. 2 shows XRD spectra of the glass, taken after pre-annealing for 42 days at 573 K in the pre-annealed state (state a, spectrum a); and after subsequent crystallization by heating in the DSC up to 713.5 K, according to 15% (state b, spectrum b); to 716.3 K, according to 40% (state c, spectrum c); and to 733.2 K, according to 100% (state d, spectrum d) of the heat release of the main crystallization peak in the DSC spectrum. Each of the shown spectra represents a certain state (a–d) in the pathway of crystallization. As a reference, one spectrum is taken after partial crystallization of the as-quenched glass up to 100% of the heat release of the main crystallization peak (state e, spectrum e). The XRD spectra taken after only pre-annealing (state a) does not differ from the diffuse scattering spectrum typical for the as-quenched state. Even prolonged annealing of the glass for 12 weeks (84 days) at 573 K (not shown
Fig. 2. XRD spectra of V4 glass taken after different heat treatments. (a) Pre-annealed for 42 days at 573 K, (b)–(d): pre-annealed for 42 days at 573 K and subsequently heated in the DSC with a heating rate of 4 K/min up to (b) 713.5 K, (c) 716.3 K, (d) 733.2 K, and (e) heated in the DSC from the as-quenched state up to 745 K. Indication of Bragg peaks: “o”, QX2 ; “+”, X1 .
S. Mechler et al. / Materials Science and Engineering A 375–377 (2004) 355–358
Fig. 3. TEM image of the decomposed V4 glass after annealing for 42 days at 573 K and the corresponding electron diffraction pattern.
in the figure) does not lead to any change in the XRD spectrum. After heating the pre-annealed glass up to 713.5 K (state b) several Bragg peaks superimposed on the diffuse spectrum of the amorphous phase can be seen in the XRD spectrum. These Bragg peaks correspond to a quasicrystalline phase (QX2 ), as will be shown later. They are narrow, indicating a rather coarse grained microstructure. After heating the annealed glass up to 716.3 K (state c) the Bragg peaks have become larger, indicating further growth of the quasicrystalline phase. Additional Bragg peaks of at least one further crystalline phase can be detected in the spectrum after heating the pre-annealed glass up to 733.2 K (state d). The microstructure mainly consists of one crystalline phase X1 (indicated as “+” in the figure) and the quasicrystalline phase QX2 (indicated as “o” in the figure). The XRD spectrum of the sample, heated from the as-quenched state up to 745 K (state e) shows Bragg peaks of the phase X1 , only small amounts of further crystalline phases are present. No Bragg peaks of the quasicrystalline phase are discernible. Only when heated up to 873 K, new phases (e.g. modified Be2 Zr and a Zr2 Cu like phase) appear in the microstructure. TEM analysis of the as-quenched glass reveals a completely homogeneous amorphous phase, whereas bright spots in the corresponding TEM image of the pre-annealed sample (state a) indicate inhomogeneities (Fig. 3). The bright regions, with a typical size of about 30–40 nm, are surrounded by a darker border. The electron diffraction pattern, which does not show any Bragg spots, indicates the amorphous nature of the pre-annealed material (see also XRD spectrum a in Fig. 2). The decomposition of the glass was also established by analysis with the three dimensional atom probe. The microhardness of the as-quenched glass of about 5.7 GPa remains unchanged after pre-annealing for even 12 weeks, whereas already partial crystallization increases the microhardness significantly. The TEM image (Fig. 4) of a sample heated up to 709 K, according to 4% of the heat release of the main crystallization peak in the DSC spectrum shows dark polygons with a typical size of about
357
Fig. 4. TEM image of the decomposed and partially crystallized V4 glass after annealing for 42 days at 573 K and subsequent heating in the DSC with a heating rate of 4 K/min up to 709 K.
40–250 nm embedded in the decomposed amorphous matrix. It is noted, that the bright regions, which could be seen in Fig. 3 have become larger. After heating the pre-annealed sample up to 733.2 K (state d), the bright regions are grown up to 800 nm in diameter, as was observed by SEM (not shown here). Fig. 5 shows a HRTEM image of one polygon. The corresponding diffraction pattern shows a five-fold symmetry, which is typical for a quasicrystalline phase. The lattice fringe distances in the direction of the different axis of the lattice show that these quasicrystals are not of the same type as the quasicrystals QX1 , which develop during annealing the V4 glass at 643 K (i.e. above Tg ) as a first stage phase [12]. In contrast to the transient quasicrystalline phase QX1 , the phase QX2 seems to be rather stable. After an annealing for 3 h at 693 K of the pre-annealed glass the Bragg peaks of the QX2 phase are still present in a XRD spectrum (not shown here) where they had grown during the first hour of annealing. Future analysis will clear the structure type of this quasicrystalline phase.
Fig. 5. HRTEM image with the five-fold zone axis of a quasicrystal, which has formed during heating in the DSC (4 K/min) up to 709 K after pre-annealing for 42 days at 573 K and the corresponding nanobeam electron diffraction pattern.
358
S. Mechler et al. / Materials Science and Engineering A 375–377 (2004) 355–358
4. Conclusions During long time annealing of the V4 alloy at temperatures well below Tg not only reversible microstructural alterations do occur. For prolonged times, decomposition into two amorphous phases takes place, leading to the formation of a rather stable quasicrystalline phase during heating of the pre-annealed alloy. The structure of this phase and the microstructure of the crystallized glass differs significantly from that quasicrystalline phase, which develops during crystallization of an as-quenched glass, thus indicating the strong effect of the thermal history on the crystallization behavior of the glass.
[3] [4] [5] [6] [7] [8] [9] [10]
References
[11] [12]
[1] W.L. Johnson, Mater. Sci. Forum 225–227 (1996) 35–50; W.L. Johnson, MRS Bull. 24 (1999) 2–56. [2] M.-P. Macht, N. Wanderka, A. Wiedenmann, H. Wollenberger, Q. Wei, S.G. Klose, A. Sagel, H.J. Fecht, in: Proceedings of the MRS
[13] [14]
Symposium, vol. 398, MRS, Pittsburgh, PA, USA, 1996, pp. 375– 380. A. Wiedenmann, J.-M. Liu, Solid State Commun. 100 (1996) 331– 335. S. Schneider, U. Geyer, P. Thiyagarajan, W.L. Johnson, Mater. Sci. Forum 235–238 (1997) 337–342. H. Herrmann, A. Wiedemann, P. Uebele, J. Phys.: Condens. Matter 9 (1997) L509–L515. J.F. Loeffler, P. Thiyagarajan, W.L. Johnson, J. Appl. Crystallogr. 33 (2000) 500. T.A. Waniuk, J. Schroers, W.L. Johnson, Appl. Phys. Lett. 78 (2001) 1213–1215. Q. Wei, N. Wanderka, P. Schubert-Bischoff, M.-P. Macht, S. Friedrich, J. Mater. Res. 15 (8) (2000) 1729–1734. J. Schroers, R. Busch, A. Masuhr, W.L. Johnson, Appl. Phys. Lett. 74 (1999) 2806–2808. M.-P. Macht, Q. Wei, N. Wanderka, I. Sieber, N. Deyneka, Mater. Sci. Forum 343–346 (2000) 173–178. N. Wanderka, M.-P. Macht, M. Seidel, S. Mechler, K. Stahl, J.Z. Jiang, Appl. Phys. Lett. 77 (2000) 3935–3937. M.-P. Macht, S. Mechler, M. Mueller, N. Wanderka, Mater. Sci. Forum 386–388 (2002) 99–104. T. Zumkley, V. Naundorf, M.-P. Macht, G. Frohberg, Mater. Sci. Forum 386–388 (2002) 65–70. R. Bruening, J.O. Stroem-Olsen, Phys. Rev. B 41 (1990) 2678–2683.