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Ti-based amorphous alloys with a large supercooled liquid region
Materials Science and Engineering A304–306 (2001) 771–774
Ti-based amorphous alloys with a large supercooled liquid region Tao Zhang∗ , Akihisa Inoue Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Abstract A new amorphous alloy system of Ti-Cu-Ni-B-Sn-Si with high thermal stability of supercooled liquid was found. The temperature interval of the supercooled liquid region before crystallization was above 70 K. The glass transition temperature (Tg ) and the reduced glass transition temperature (Tg /Tm ) of the Ti50 Cu20 Ni24 B1 Si2 Sn3 alloy are 726 K and 0.59, respectively. The high thermal stability of the supercooled liquid as well as the high Tg /Tm leads to the production of bulk amorphous alloy with a diameter up to 1 mm by copper mold casting. The Vickers hardness, Young’s modulus and tensile fracture strength of the 1 mm diameter bulk amorphous alloy are 620, 110 GPa and 2100 MPa, respectively. The fracture surface exhibits a vein-like morphology, typical for many ductile amorphous alloys. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Amorphous alloy system; Thermal stability; Supercooled liquid
1. Introduction Exploring amorphous alloys with a large supercooled liquid region before crystallization is of great importance because the appearance of the large supercooled liquid region is expected to cause the production of a bulk amorphous alloy. For the last one decade, a number of bulk amorphous alloys have been developed in multi-component systems such as La-Al-TM [1], Zr-M-TM [2], Zr-Be-TM [3], Pd-TM-P [4] and Fe-(Zr, Nb, Ta)-B [5] (La = Lanthanide metal, TM = IV to VIII group transition metals) systems. These new alloy systems have enabled us to produce bulk amorphous alloys by various solidification methods and the largest thickness has reached about 30 mm [6] for the Zr-based alloys and about 75 mm [7] for the Pd-based alloys. The bulk amorphous alloys, represented by the Zr-based ones, have already gained actual applications by utilizing their high glass-forming ability, unique mechanical properties and good viscous flow workability. On the other hand, if the specific strength increases further, the application field of the bulk amorphous alloys can be expected to be significantly extended. Aiming to this problem, we have explored new amorphous alloys in Ti-based system and found that a large supercooled liquid region over 60 K is observed in the Ti-Ni-Cu-Sn [8] and Ti-Ni-Cu-Si-B [9] systems. Furthermore, this paper is intended to present new Ti-Cu-Ni-Si-Sn-B amorphous alloys with a large supercooled region before crystallization, high thermal stability and good mechanical properties. The effect of adding B, ∗
Corresponding author.
Si and Sn simultaneously on the thermal stability of the supercooled liquid and glass forming ability was also investigated.
2. Experimental procedure The master alloy ingots were prepared by arc melting the mixture of pure metals, B and Si in an argon atmosphere. The amorphous rod samples of 1 mm in diameter were produced by casting the pre-alloyed ingots into copper molds in an argon atmosphere. Amorphous ribbon samples of about 20 m in thickness and about 1 mm in width were also produced by melt spinning. The amorphous structure was examined by X-ray diffractometry, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The melting temperature was also measured by differential thermal analysis (DTA). Mechanical properties were measured with an Instron testing machine and a Vickers microhardness tester at room temperature. Fracture surface was examined by scanning electron microscopy (SEM).
3. Results and discussion Fig. 1 shows the outer surface appearance of the rod amorphous alloy prepared by the metallic mold casting method. The cast sample has smooth outer surfaces and pronounced metallic luster typical for an amorphous alloy without grain boundaries. No distinct contrast revealing the precipitation of crystalline phase can be seen over the outer surface.
0921-5093/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 5 0 9 3 ( 0 0 ) 0 1 5 9 2 - 6
772
T. Zhang, A. Inoue / Materials Science and Engineering A304–306 (2001) 771–774
Fig. 1. Cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous rod prepared by copper mold casting.
Furthermore, the dimension of the sample is nearly the same as that for the inner cavity of the copper mold, indicating that the Ti-Cu-Ni-B-Si-Sn alloy has a good castability. The X-ray diffraction patterns shown in Fig. 2, a main halo peak with a wave vector Kp (= 4π sin θ/λ) around 29.7 nm−1 , and no crystalline peak is seen for the 1 mm diameters sample as well as the 20 m ribbon sample. Besides, the optical micrograph of the cross section of the rod sample also reveals a featureless contrast in an etched state using a hydrogen fluoride acid. These results indicate that the bulk rod is composed of an amorphous phase. Fig. 3 shows the DSC curve of the amorphous Ti50 Ni24 Cu20 B1 Si2 Sn3 rod with a diameter of 1 mm, together with the data of the melt-spun amorphous ribbon with a thickness of 20 m. The rod alloy shows a glass transition at T g = 726 K, followed by the supercooled liquid region with a temperature interval of 74 K and then crystalliza-
Fig. 3. Differential scanning calorimetric curve of the cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous alloy with a diameter of 1 mm. The data of the metal-spun Ti-Ni-Cu-B-Si-Sn amorphous ribbon with a thickness of 20 m are also shown for comparison.
Fig. 2. X-ray diffraction pattern of the cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous rod with diameter of 1 mm. The data of the metal-spun Ti-Ni-Cu-B-Si-Sn amorphous ribbon with a thickness of 20 m are also shown for comparison.
tion at T x = 800 K. The feature of the phase transition and the thermal properties of Tg , 1Tx and Tx for the rod alloy are nearly the same as those for the ribbon. The single exothermic peak results from the simultaneous precipitation of several kinds of crystalline phases. The crystallization mode implies that the atomic rearrangements of the constituent elements on a long-range scale are necessary for the progress of the crystallization reaction. The necessity causes the retardation of crystallization reaction which leads to the high thermal stability of the supercooled liquid. The simultaneous precipitation of the crystalline phases through the
T. Zhang, A. Inoue / Materials Science and Engineering A304–306 (2001) 771–774
773
Fig. 4. Differential thermal analytical curve of the Ti50 Ni24 Cu20 B1 Si2 Sn3 alloy.
single-stage exothermic reaction is in agreement with that for other multi-component amorphous alloys with the supercooled liquid region exceeding 70 K before crystallization. The large 1Tx for the Ti-based amorphous alloys can be understood in the framework of the three empirical rules [10] for the achievement of large GFA, i.e. (1) multi-component alloy systems consisting of more than three elements, (2) significantly different atomic size ratios above about 12% among the main constituent elements, and (3) negative heats of mixing among the elements. The base composition in the presented alloys is the Ti-Ni-Cu system, which satisfies the three empirical rules. The addition of B, Si and Sn is effective for increase in the degree of the satisfaction of the empirical rules. In the supercooled liquid in which the three empirical rules are satisfied at a higher level, the topological and chemical short-range orderings are enhanced, leading to the formation of a highly dense random packed structure with low atomic diffusivity. It is generally believed that the higher the packing density, the higher the thermal stability and the higher the resistance of the supercooled liquid against transformation into crystalline phase [2]. The rearrangement of the constituent elements with different atomic sizes leads to a higher packing density. Moreover, the generation of atomic pairs with various negative heats of mixing also increases the thermal stability of the supercooled liquid since a large amount of active energy is required for crystallization. In the Ti-Ni-Cu-B-Si-Sn system, the atomic sizes change more continuously in the order of Ti > Sn > Ni ≈ Cu > Si > B, which may further increase the packing density as compared with Ti-Ni-Cu ternary alloys. Furthermore, the addition of
Fig. 5. Scanning electron micrograph of the tensile fracture surface appearance of the cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous rod with a diameter of 1 mm.
B, Si and Sn effectively increases the numbers of atomic pairs with negative heats of mixing, such as Ti-(Si, B, Sn) as well as Ni-(Si, B, Sn). Therefore, both supercooled liquid region and glass-forming ability increase with an increase of packing density and atomic pairs resulting from the ternary to the multi-component of Ti-Ni-Cu-B-Si-Sn.
Table 1 Mechanical and thermal properties of the Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous alloy rod Vikers hardness
Young’s modulus (GPa)
Tensile strength (MPa)
Glass transition Tg (K)
Crystallization Tx (K)
Supercooled liquid region 1Tx (K)
620
110
2100
726
800
74
774
T. Zhang, A. Inoue / Materials Science and Engineering A304–306 (2001) 771–774
Fig. 4 shows the DTA curve of the glassy alloy measured with a heating rate of 0.33 K/s. A distinct endothermic reaction due to melting is seen in the temperature range between 1230 and 1310 K. The composition was believed to be very close to a eutectic one and hence the solidus temperature of 1230 K is determined as eutectic temperature. Taking T g = 726 and T m = 1230 K, tg = T g /T m = 0.59 is obtained at the eutectic composition. Table 1 summarizes the Vikers hardness, Young’s modulus, tensile fracture strength and thermal stability for the amorphous Ti50 Ni24 Cu20 B1 Si2 Sn3 alloys. The Vickers hardness, Young’s modulus, tensile fracture strength are 620, 110 GPa and 2100 MPa, respectively, which exceed those for Zr-base bulk amorphous alloys. Fig. 5 shows the tensile fracture behavior. The tensile fracture surface appearance for the amorphous Ti50 Ni24 Cu20 B1 Si2 Sn3 rod. The fracture occurs along the maximum shear plane which is declined by about 45◦ to the direction of tensile load. The fracture surface exhibits a vein-like morphology, typical for ductile amorphous alloys. The well-developed veins suggests that local melting occurs during final fracture. 4. Conclusions New Ti-Cu-Ni-Si-Sn amorphous alloys were developed and the thermal stability of the supercooled liquid region
and the reduced glass transition temperature were investigated. The supercooled liquid region is over 70 K for the Ti50 Ni24 Cu20 B1 Si2 Sn3 alloy. The maximal reduced glass transition temperature (Tg /Tm ) reaches 0.59. The high thermal stability of the supercooled liquid as well as the high reduced glass transition temperature leads to the production of bulk amorphous alloy in the diameter range up to 1 mm by copper mold casting. The Vikers hardness, Young’s modulus and tensile fracture strength of the bulk amorphous alloys are 620, 110 GPa and 2100 MPa, respectively. The fracture surface consists mainly of a vein-like pattern, typical for ductile amorphous alloys. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
A. Inoue, T. Zhang, T. Masumoto, Mater. Trans. JIM 30 (1989) 965. T. Zhang, A. Inoue, T. Masumoto, Mater. Trans. 32 (1991) 1005. A. Peker, W.L. Johnson, Appl. Phys. Lett. 63 (1993) 2342. A. Inoue, N. Nisiyama, T. Masumoto, Mater. Trans. JIM 37 (1996) 181. A. Inoue, T. Zhang, A. Takeuchi, Appl. Phys. Lett. 71 (1997) 464. A. Inoue, T. Zhang, Mater. Trans. JIM 37 (1996) 185. A. Inoue, N. Nishiyama, H.M. Kimura, Mater. Trans. JIM 38 (1997) 179. T. Zhang, A. Inoue, Mater. Trans. JIM 39 (1998) 1001. T. Zhang, A. Inoue, Mater. Trans. JIM 40 (1999) 301. A. Inoue, T. Zhang, T. Masumoto, J. Non-Cryst. Solids 156–158 (1993) 473.
Ti-based amorphous alloys with a large supercooled liquid region Tao Zhang∗ , Akihisa Inoue Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
Abstract A new amorphous alloy system of Ti-Cu-Ni-B-Sn-Si with high thermal stability of supercooled liquid was found. The temperature interval of the supercooled liquid region before crystallization was above 70 K. The glass transition temperature (Tg ) and the reduced glass transition temperature (Tg /Tm ) of the Ti50 Cu20 Ni24 B1 Si2 Sn3 alloy are 726 K and 0.59, respectively. The high thermal stability of the supercooled liquid as well as the high Tg /Tm leads to the production of bulk amorphous alloy with a diameter up to 1 mm by copper mold casting. The Vickers hardness, Young’s modulus and tensile fracture strength of the 1 mm diameter bulk amorphous alloy are 620, 110 GPa and 2100 MPa, respectively. The fracture surface exhibits a vein-like morphology, typical for many ductile amorphous alloys. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Amorphous alloy system; Thermal stability; Supercooled liquid
1. Introduction Exploring amorphous alloys with a large supercooled liquid region before crystallization is of great importance because the appearance of the large supercooled liquid region is expected to cause the production of a bulk amorphous alloy. For the last one decade, a number of bulk amorphous alloys have been developed in multi-component systems such as La-Al-TM [1], Zr-M-TM [2], Zr-Be-TM [3], Pd-TM-P [4] and Fe-(Zr, Nb, Ta)-B [5] (La = Lanthanide metal, TM = IV to VIII group transition metals) systems. These new alloy systems have enabled us to produce bulk amorphous alloys by various solidification methods and the largest thickness has reached about 30 mm [6] for the Zr-based alloys and about 75 mm [7] for the Pd-based alloys. The bulk amorphous alloys, represented by the Zr-based ones, have already gained actual applications by utilizing their high glass-forming ability, unique mechanical properties and good viscous flow workability. On the other hand, if the specific strength increases further, the application field of the bulk amorphous alloys can be expected to be significantly extended. Aiming to this problem, we have explored new amorphous alloys in Ti-based system and found that a large supercooled liquid region over 60 K is observed in the Ti-Ni-Cu-Sn [8] and Ti-Ni-Cu-Si-B [9] systems. Furthermore, this paper is intended to present new Ti-Cu-Ni-Si-Sn-B amorphous alloys with a large supercooled region before crystallization, high thermal stability and good mechanical properties. The effect of adding B, ∗
Corresponding author.
Si and Sn simultaneously on the thermal stability of the supercooled liquid and glass forming ability was also investigated.
2. Experimental procedure The master alloy ingots were prepared by arc melting the mixture of pure metals, B and Si in an argon atmosphere. The amorphous rod samples of 1 mm in diameter were produced by casting the pre-alloyed ingots into copper molds in an argon atmosphere. Amorphous ribbon samples of about 20 m in thickness and about 1 mm in width were also produced by melt spinning. The amorphous structure was examined by X-ray diffractometry, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The melting temperature was also measured by differential thermal analysis (DTA). Mechanical properties were measured with an Instron testing machine and a Vickers microhardness tester at room temperature. Fracture surface was examined by scanning electron microscopy (SEM).
3. Results and discussion Fig. 1 shows the outer surface appearance of the rod amorphous alloy prepared by the metallic mold casting method. The cast sample has smooth outer surfaces and pronounced metallic luster typical for an amorphous alloy without grain boundaries. No distinct contrast revealing the precipitation of crystalline phase can be seen over the outer surface.
0921-5093/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 5 0 9 3 ( 0 0 ) 0 1 5 9 2 - 6
772
T. Zhang, A. Inoue / Materials Science and Engineering A304–306 (2001) 771–774
Fig. 1. Cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous rod prepared by copper mold casting.
Furthermore, the dimension of the sample is nearly the same as that for the inner cavity of the copper mold, indicating that the Ti-Cu-Ni-B-Si-Sn alloy has a good castability. The X-ray diffraction patterns shown in Fig. 2, a main halo peak with a wave vector Kp (= 4π sin θ/λ) around 29.7 nm−1 , and no crystalline peak is seen for the 1 mm diameters sample as well as the 20 m ribbon sample. Besides, the optical micrograph of the cross section of the rod sample also reveals a featureless contrast in an etched state using a hydrogen fluoride acid. These results indicate that the bulk rod is composed of an amorphous phase. Fig. 3 shows the DSC curve of the amorphous Ti50 Ni24 Cu20 B1 Si2 Sn3 rod with a diameter of 1 mm, together with the data of the melt-spun amorphous ribbon with a thickness of 20 m. The rod alloy shows a glass transition at T g = 726 K, followed by the supercooled liquid region with a temperature interval of 74 K and then crystalliza-
Fig. 3. Differential scanning calorimetric curve of the cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous alloy with a diameter of 1 mm. The data of the metal-spun Ti-Ni-Cu-B-Si-Sn amorphous ribbon with a thickness of 20 m are also shown for comparison.
Fig. 2. X-ray diffraction pattern of the cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous rod with diameter of 1 mm. The data of the metal-spun Ti-Ni-Cu-B-Si-Sn amorphous ribbon with a thickness of 20 m are also shown for comparison.
tion at T x = 800 K. The feature of the phase transition and the thermal properties of Tg , 1Tx and Tx for the rod alloy are nearly the same as those for the ribbon. The single exothermic peak results from the simultaneous precipitation of several kinds of crystalline phases. The crystallization mode implies that the atomic rearrangements of the constituent elements on a long-range scale are necessary for the progress of the crystallization reaction. The necessity causes the retardation of crystallization reaction which leads to the high thermal stability of the supercooled liquid. The simultaneous precipitation of the crystalline phases through the
T. Zhang, A. Inoue / Materials Science and Engineering A304–306 (2001) 771–774
773
Fig. 4. Differential thermal analytical curve of the Ti50 Ni24 Cu20 B1 Si2 Sn3 alloy.
single-stage exothermic reaction is in agreement with that for other multi-component amorphous alloys with the supercooled liquid region exceeding 70 K before crystallization. The large 1Tx for the Ti-based amorphous alloys can be understood in the framework of the three empirical rules [10] for the achievement of large GFA, i.e. (1) multi-component alloy systems consisting of more than three elements, (2) significantly different atomic size ratios above about 12% among the main constituent elements, and (3) negative heats of mixing among the elements. The base composition in the presented alloys is the Ti-Ni-Cu system, which satisfies the three empirical rules. The addition of B, Si and Sn is effective for increase in the degree of the satisfaction of the empirical rules. In the supercooled liquid in which the three empirical rules are satisfied at a higher level, the topological and chemical short-range orderings are enhanced, leading to the formation of a highly dense random packed structure with low atomic diffusivity. It is generally believed that the higher the packing density, the higher the thermal stability and the higher the resistance of the supercooled liquid against transformation into crystalline phase [2]. The rearrangement of the constituent elements with different atomic sizes leads to a higher packing density. Moreover, the generation of atomic pairs with various negative heats of mixing also increases the thermal stability of the supercooled liquid since a large amount of active energy is required for crystallization. In the Ti-Ni-Cu-B-Si-Sn system, the atomic sizes change more continuously in the order of Ti > Sn > Ni ≈ Cu > Si > B, which may further increase the packing density as compared with Ti-Ni-Cu ternary alloys. Furthermore, the addition of
Fig. 5. Scanning electron micrograph of the tensile fracture surface appearance of the cast Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous rod with a diameter of 1 mm.
B, Si and Sn effectively increases the numbers of atomic pairs with negative heats of mixing, such as Ti-(Si, B, Sn) as well as Ni-(Si, B, Sn). Therefore, both supercooled liquid region and glass-forming ability increase with an increase of packing density and atomic pairs resulting from the ternary to the multi-component of Ti-Ni-Cu-B-Si-Sn.
Table 1 Mechanical and thermal properties of the Ti50 Ni24 Cu20 B1 Si2 Sn3 amorphous alloy rod Vikers hardness
Young’s modulus (GPa)
Tensile strength (MPa)
Glass transition Tg (K)
Crystallization Tx (K)
Supercooled liquid region 1Tx (K)
620
110
2100
726
800
74
774
T. Zhang, A. Inoue / Materials Science and Engineering A304–306 (2001) 771–774
Fig. 4 shows the DTA curve of the glassy alloy measured with a heating rate of 0.33 K/s. A distinct endothermic reaction due to melting is seen in the temperature range between 1230 and 1310 K. The composition was believed to be very close to a eutectic one and hence the solidus temperature of 1230 K is determined as eutectic temperature. Taking T g = 726 and T m = 1230 K, tg = T g /T m = 0.59 is obtained at the eutectic composition. Table 1 summarizes the Vikers hardness, Young’s modulus, tensile fracture strength and thermal stability for the amorphous Ti50 Ni24 Cu20 B1 Si2 Sn3 alloys. The Vickers hardness, Young’s modulus, tensile fracture strength are 620, 110 GPa and 2100 MPa, respectively, which exceed those for Zr-base bulk amorphous alloys. Fig. 5 shows the tensile fracture behavior. The tensile fracture surface appearance for the amorphous Ti50 Ni24 Cu20 B1 Si2 Sn3 rod. The fracture occurs along the maximum shear plane which is declined by about 45◦ to the direction of tensile load. The fracture surface exhibits a vein-like morphology, typical for ductile amorphous alloys. The well-developed veins suggests that local melting occurs during final fracture. 4. Conclusions New Ti-Cu-Ni-Si-Sn amorphous alloys were developed and the thermal stability of the supercooled liquid region
and the reduced glass transition temperature were investigated. The supercooled liquid region is over 70 K for the Ti50 Ni24 Cu20 B1 Si2 Sn3 alloy. The maximal reduced glass transition temperature (Tg /Tm ) reaches 0.59. The high thermal stability of the supercooled liquid as well as the high reduced glass transition temperature leads to the production of bulk amorphous alloy in the diameter range up to 1 mm by copper mold casting. The Vikers hardness, Young’s modulus and tensile fracture strength of the bulk amorphous alloys are 620, 110 GPa and 2100 MPa, respectively. The fracture surface consists mainly of a vein-like pattern, typical for ductile amorphous alloys. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
A. Inoue, T. Zhang, T. Masumoto, Mater. Trans. JIM 30 (1989) 965. T. Zhang, A. Inoue, T. Masumoto, Mater. Trans. 32 (1991) 1005. A. Peker, W.L. Johnson, Appl. Phys. Lett. 63 (1993) 2342. A. Inoue, N. Nisiyama, T. Masumoto, Mater. Trans. JIM 37 (1996) 181. A. Inoue, T. Zhang, A. Takeuchi, Appl. Phys. Lett. 71 (1997) 464. A. Inoue, T. Zhang, Mater. Trans. JIM 37 (1996) 185. A. Inoue, N. Nishiyama, H.M. Kimura, Mater. Trans. JIM 38 (1997) 179. T. Zhang, A. Inoue, Mater. Trans. JIM 39 (1998) 1001. T. Zhang, A. Inoue, Mater. Trans. JIM 40 (1999) 301. A. Inoue, T. Zhang, T. Masumoto, J. Non-Cryst. Solids 156–158 (1993) 473.