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Akihisa Inoue - One of the best experts on this subject based on the ideXlab platform.

  • novel deformation induced polymorphic crystallization and softening of al based Amorphous Alloys
    Acta Materialia, 2018
    Co-Authors: H W Bi, Elsayed Shalaan, F Almarzouki, Akihisa Inoue, F L Kong, A L Greer
    Abstract:

    Abstract Melt-spun Amorphous ribbons of Al90Y10 (at.%) (90Al) and Al84Y8.5Ni4Co2Pd1Fe0.5 (84Al) are cold-rolled at near to liquid-nitrogen temperature or at room temperature, inducing partial crystallization to nanoscale fcc-Al (α-Al). The crystallization is characterized and contrasted with the distinct sequences of reactions on annealing 90Al and 84Al Amorphous Alloys. Rolling-induced crystallization leads to softening, opposite to the effect of nanocrystallization induced by annealing. The origins of the hardness changes are analyzed. The rolling induces novel polymorphic crystallization to α-Al with extended solid solubility. This transformation, which occurs equally in 84Al and 90Al, despite the much greater thermal stability of the former, allows the ribbons to retain good bending ductility, and delays the onset of embrittlement on subsequent annealing. Partial crystallization induced by cold-rolling is useful in avoiding the formation of compound phases associated with brittleness, and is a promising process for high-solute Al-based Amorphous Alloys to be further developed as structural materials.

  • correlation of atomic packing with the boson peak in Amorphous Alloys
    Journal of Applied Physics, 2014
    Co-Authors: Akihisa Inoue, Chuntao Chang, Weiming Yang, Guofu Chen, Y C Zhao, Baolong Shen, Renwen Li
    Abstract:

    Boson peaks (BP) have been observed from phonon specific heats in 10 studied Amorphous Alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied Amorphous Alloys and 56 reported Amorphous Alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in Amorphous Alloys, and (b) the atomic packing in Amorphous Alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied Amorphous Alloys. This finding provides a new perspective for atomic packing in Amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.

  • hydrogen permeation and structural features of melt spun ni nb zr Amorphous Alloys
    Acta Materialia, 2005
    Co-Authors: Shinichi Yamaura, Eiichiro Matsubara, Hisamichi Kimura, Masaki Sakurai, Masashi Hasegawa, Kimio Wakoh, Yoichiro Shimpo, Motonori Nishida, Akihisa Inoue
    Abstract:

    Abstract Amorphous (Ni 0.6 Nb 0.4 ) 100− x Zr x ( x  = 0, 20, 30, 40 and 50 at.%) Alloys were prepared by the melt-spinning technique, and the hydrogen permeation through those alloy membranes was examined. The local atomic structure in these Alloys was also investigated by radial distribution function (RDF) analysis. Moreover, hydrogen solubility and diffusivity were also measured in order to discuss the mechanism for hydrogen permeation. The permeability of the Ni–Nb–Zr Amorphous Alloys increases with Zr content and temperature. The maximum hydrogen permeability is 1.59 × 10 −8  mol m −1  s −1  Pa −1/2 at 673 K for the (Ni 0.6 Nb 0.4 ) 50 Zr 50 Amorphous alloy. The (Ni 0.6 Nb 0.4 ) 50 Zr 50 Amorphous alloy showed larger hydrogen solubility and diffusivity than the (Ni 0.6 Nb 0.4 ) 70 Zr 30 Amorphous alloy. As the result, the (Ni 0.6 Nb 0.4 ) 50 Zr 50 Amorphous alloy showed higher hydrogen permeability than the (Ni 0.6 Nb 0.4 ) 70 Zr 30 Amorphous alloy at 673 K. The RDF analysis shows that the atomic distance between the Zr atoms increases by hydrogenation. The chemical ordering such that the number of Zr coordinates is much higher than that of Ni and Nb coordinates was found in the (Ni 0.6 Nb 0.4 ) 70 Zr 30 and (Ni 0.6 Nb 0.4 ) 50 Zr 50 Amorphous Alloys. The relation between the Amorphous local structure and the permeation was discussed in detail.

  • soft magnetic properties of fe co re b Amorphous Alloys with a large supercooled liquid region
    Materials Transactions, 2001
    Co-Authors: Wei Zhang, Akihisa Inoue
    Abstract:

    Fe-based Amorphous Alloys with high B concentrations in (Fe, Co)-RE-B system were found to exhibit a large supercooled liquid region (ΔT x ) in a composition range 22.5-30 at%B, 0-30 at%Co and 2.5-6 at%RE. The ΔT x values exceeding 50K were obtained for a series of Fe 62 Co 9.5 RE 3.5 B 25 (RE = Pr, Nd, Sm, Gd, Tb, Dy, Er) Amorphous Alloys. The Fe 62 Co 9.5 RE 3.5 B 25 Amorphous Alloys exhibit good soft magnetic properties of 1.35 to 1.43 T for saturation magnetization, 1.0 to 3.8 A/m for coercive force, and 8300 to 12500 for permeability at 1 kHz in the annealed state for 600 s at 773 K. The synthesis of the (Fe,Co)-RE-B Amorphous Alloys exhibiting a large supercooled liquid region and good soft magnetic properties with a high saturation magnetization is promising for future development as a new type of soft magnetic material.

  • the micro formability of zr based Amorphous Alloys in the supercooled liquid state and their application to micro dies
    Journal of Materials Processing Technology, 2001
    Co-Authors: Yasunori Saotome, Tao Zhang, Seiji Miwa, Akihisa Inoue
    Abstract:

    Abstract Zr-based Amorphous Alloys exhibit an obvious glass transition phenomenon and supercooled liquid state over a wide temperature range. In the present paper, the authors study the macroscopic and microscopic deformation behavior of Zr–Al–Cu and Zr–Al–Cu–Ni Amorphous Alloys. On a macroscopic scale, the materials exhibit a Newtonian viscous flow in the supercooled liquid state. To evaluate the micro-formability of the materials, the authors developed an evaluation system using a micro-V-grooved die made of (1 0 0) silicon that has been processed by electron beam lithography and anisotropic etching and employed this system to quantitatively evaluate the microscopic formability of the materials. The V-groove is from 1 to 20 μm wide and has a base angle of 70.6°. The material was subjected to the newly developed micro-forging apparatus and was die forged with micro-V-grooved dies. After the deformation, the shape of the specimen was measured using a three-dimensional shape measurement system with a highly sensitive detector in a scanning electron microscope. These geometrical analyses of deformed specimens confirmed the superior formability on a micrometer scale and indicated the possibility of fabricating very fine micro-parts such as those for micro-electro-mechanical systems (MEMS). Furthermore, the material is stable under the glass transition temperature Tg, and can thus be used as a fine micro-forging die for some plastic materials or other Amorphous Alloys with a glass transition temperature below Tg. In the present paper, it was confirmed that Zr–Al–Cu Amorphous alloy could be used as a micro-die for forming La–Al–Ni Amorphous alloy. As a result, it was demonstrated that Amorphous Alloys are potential micro-materials for fabricating various micro-parts or micro-dies because of their superior mechanical characteristics and homogeneity on a microscopic scale.

Tao Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Application of 3D Balanced Growth Theory to the Formation of Bulk Amorphous Alloys
    'Frontiers Media SA', 2021
    Co-Authors: Yong Zhang, Tao Zhang
    Abstract:

    Since the emergence of Amorphous Alloys as a new class of materials, efficiency improvements have been made in optimizing the fabrication process, the mechanization of alloy formation, and the size of the Alloys themselves. Amorphous Alloys have been used in precision instruments as they possess excellent magnetic properties, corrosion resistance, wear resistance, high strength, hardness, toughness, high electrical resistivity, and electromechanical coupling properties. Because their hysteresis losses are lower than those of traditional transformer cores, the conversion efficiency of equipment has been significantly improved, thereby saving energy and protecting the environment. Hence, Amorphous iron cores have replaced traditional materials. Amorphous Alloys also show excellent performance as anti-corrosion and wear-resistant coatings. The process of preparing Amorphous Alloys starts with an Amorphous alloy film obtained by evaporation deposition and then proceeds to the use of a high cooling rate ribbon spinning method to finally obtain a thin strip of an Amorphous alloy. A widely used method of copper mold suction casting is then used to prepare the bulk Amorphous alloy. The sizes of Amorphous Alloys have been continually increasing, which has resulted in increasingly serious challenges, such as cooling rate and thermal stability limitations. In addition, crystals can form at low cooling rates. The latent heat of crystallization is released when crystals are formed, which causes damage to the Amorphous area so that the size of Amorphous Alloys is reduced. Because of these difficulties, new processes that eliminate the cooling rate gradient, such as 3D additive manufacturing, ultrasonic production, and mold design, combined with the concept of “entropy control” component design and the economic theory of “balanced development,” lead to a three-dimensional bulk Amorphous alloy being proposed. The theory of balanced growth provides a new concept for the development and application of bulk Amorphous Alloys. This review offers a retrospective view of recent studies of Amorphous Alloys and provides a description of the formation of Amorphous Alloys and Amorphous phases and the criteria required to predict the successful formation of Amorphous Alloys. Then, we address the problem of size limitation confronting current production methods. The three-dimensional balanced growth theory of bulk Amorphous Alloys was formulated from a flexible adaptation of the balanced growth theory of economics. We have confidence that the production and development of bulk Amorphous Alloys have a bright future

  • hard rhenium boron cobalt Amorphous Alloys with a wide supercooled liquid region
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2015
    Co-Authors: Jianfeng Wang, Shijie Zhu, Liguo Wang, Shaokang Guan, Tao Zhang
    Abstract:

    Abstract Novel Re–B–Co Amorphous Alloys with compositions of Re65−xB35Cox (at%, x=25, 30, 35, 40, 45, and 50) were fabricated by single-roller melt spinning. These Alloys were found to exhibit a clear glass transition phenomenon. The width of supercooled liquid region (ΔTx) is in the range of 52–71 K. Such a large ΔTx allows us to produce Amorphous alloy bulks by thermoplastic forming. The Vickers hardness is up to 19.10 GPa for the Re40B35Co25 alloy, which is close to that reported for some hard covalent crystals. Thus, the present Alloys with a combination of large ΔTx and high hardness are expected to be used as a new type of structural materials. Furthermore, the relationships of hardness with glass transition temperature and Young's modulus were also discussed.

  • the micro formability of zr based Amorphous Alloys in the supercooled liquid state and their application to micro dies
    Journal of Materials Processing Technology, 2001
    Co-Authors: Yasunori Saotome, Tao Zhang, Seiji Miwa, Akihisa Inoue
    Abstract:

    Abstract Zr-based Amorphous Alloys exhibit an obvious glass transition phenomenon and supercooled liquid state over a wide temperature range. In the present paper, the authors study the macroscopic and microscopic deformation behavior of Zr–Al–Cu and Zr–Al–Cu–Ni Amorphous Alloys. On a macroscopic scale, the materials exhibit a Newtonian viscous flow in the supercooled liquid state. To evaluate the micro-formability of the materials, the authors developed an evaluation system using a micro-V-grooved die made of (1 0 0) silicon that has been processed by electron beam lithography and anisotropic etching and employed this system to quantitatively evaluate the microscopic formability of the materials. The V-groove is from 1 to 20 μm wide and has a base angle of 70.6°. The material was subjected to the newly developed micro-forging apparatus and was die forged with micro-V-grooved dies. After the deformation, the shape of the specimen was measured using a three-dimensional shape measurement system with a highly sensitive detector in a scanning electron microscope. These geometrical analyses of deformed specimens confirmed the superior formability on a micrometer scale and indicated the possibility of fabricating very fine micro-parts such as those for micro-electro-mechanical systems (MEMS). Furthermore, the material is stable under the glass transition temperature Tg, and can thus be used as a fine micro-forging die for some plastic materials or other Amorphous Alloys with a glass transition temperature below Tg. In the present paper, it was confirmed that Zr–Al–Cu Amorphous alloy could be used as a micro-die for forming La–Al–Ni Amorphous alloy. As a result, it was demonstrated that Amorphous Alloys are potential micro-materials for fabricating various micro-parts or micro-dies because of their superior mechanical characteristics and homogeneity on a microscopic scale.

  • ti based Amorphous Alloys with a large supercooled liquid region
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2001
    Co-Authors: Tao Zhang, Akihisa Inoue
    Abstract:

    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 Ti50Cu20Ni24B1Si2Sn3 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.

  • formation of icosahedral quasicrystal by crystallization of zr70 ni cu pd 30 Amorphous Alloys
    Journal of Materials Research, 2001
    Co-Authors: Tao Zhang, Akihisa Inoue, Mitsuhide Matsushita, Junji Saida
    Abstract:

    An icosahedral phase was found to be formed as a primary precipitation phase in the crystallization process of binary Zr70Pd30, ternary Zr70Ni30−xPdx, and Zr70Cu30−xPdx (x = 10 and 20 at.%) and quaternary Zr70Ni10Cu10Pd10 Amorphous Alloys. The maximum volume fraction of the icosahedral phase was nearly 100% for the 20% Pd Alloys and the grain size tended to decrease in the range from 40 to 70 nm with increasing Pd content. No icosahedral phase was formed in the Zr–Ni–Cu Alloys without Pd, and hence, the addition of Pd was concluded to be essential for the formation of the icosahedral phase in the Zr-based Amorphous Alloys. It also was noticed that the icosahedral phase was formed even in the binary Zr70Pd30 Amorphous alloy. The icosahedral phase was in a metastable state and changes to equilibrium crystalline phases by annealing in the higher temperature range. The finding of the formation of the icosahedral phase in the binary alloy system allowed us to predict the future appearance of a number of icosahedral base Alloys in other alloy systems.

Akihiro Makino - One of the best experts on this subject based on the ideXlab platform.

  • fe rich soft magnetic fesibpcu hetero Amorphous Alloys with high saturation magnetization
    Materials Transactions, 2009
    Co-Authors: Liying Cui, Takeshi Kubota, Kunio Yubuta, Akihiro Makino
    Abstract:

    Magnetic properties are perhaps the most remarkable and unique properties of Fe-based Amorphous Alloys. To obtain high saturation magnetization, high Fe content is preferred. However, there is a strict upper limit of Fe content for the formation of a single Amorphous structure with good magnetic softness. Fe-based Amorphous Alloys with high Fe content over the limit have an as-quenched structure consisting of coarse � -Fe grains in an Amorphous matrix, which inevitably results in inferior magnetic softness. We have studied the effect of P and/or Cu additions on the microstructure of Fe-based Amorphous Alloys with high Fe content. The � -Fe grain size and the coercivity (Hc) decrease by the simultaneously adding P and Cu. The Fe-rich FeSiBPCu Alloys with the optimized composition have an extremely small � -Fe-like phase of about 3 nm or smaller in a diameter, exhibits the higher Js of about 1.67 T than that of the typical Fe-based Amorphous alloy and show the low coercivity (Hc) of about 4 Am � 1 in an as-quenched state. [doi:10.2320/matertrans.ME200831]

  • fe based soft magnetic Amorphous Alloys with a wide supercooled liquid region
    Journal of Applied Physics, 1999
    Co-Authors: Hisato Koshiba, Akihisa Inoue, Akihiro Makino
    Abstract:

    Amorphous Alloys with a wide supercooled liquid region (ΔTx) before crystallization were formed in the Fe56Co7Ni7Hf8M2B20 (M=Nb, Ta) Alloys by melt spinning. The ΔTx which is a critical factor of glass-forming ability, increases to large values exceeding 90 from 82 K by the addition of 2 at. % M, and the largest ΔTx value is larger by about 10 K than the largest value for recently reported (Fe,Co,Ni)–Zr–M–B Alloys. By the addition of the M metals, magnetic properties also changed. Good soft magnetic properties were obtained for the Alloys annealed for 300 s at 800 K. The saturation magnetization (Is), coercive force (Hc), and effective permeability (μe) at 1 kHz are, respectively, 0.71 T, 1.0 A/m, and 16 700 for the M=Nb alloy and 0.76 T, 1.0 A/m, and 15 600 for the M=Ta alloy. The finding of the Fe-based Amorphous Alloys exhibiting simultaneously the wide supercooled liquid region before crystallization and the good soft magnetic properties seem to enable the future development of a new ferromagnetic bul...

  • ferromagnetic co fe zr b Amorphous Alloys with glass transition and good high frequency permeability
    Applied Physics Letters, 1998
    Co-Authors: Akihisa Inoue, Takaomi Itoi, Hisato Koshiba, Akihiro Makino
    Abstract:

    A Co-based Amorphous phase with glass transition and supercooled liquid region before crystallization was formed in Co70−xFexZr10B20 and Co72−xFexZr8B20 Alloys containing more than 14 at % Fe. The crystallization temperature (Tx) is 899 K for the Co–Zr–B Alloys and remains unchanged in the Fe concentration range up to 20%. The glass transition temperature (Tg) decreases with increasing Fe content, and the ΔTx(=Tx−Tg) increases from 25 K at 14% Fe to 34 K at 21% Fe. The Amorphous Alloys with glass transition crystallize with a single stage precipitation of bcc Fe(Co) and Co3ZrB2 phases. The Co-rich Amorphous Alloys exhibit good soft magnetic properties, i.e., saturation magnetization of 0.58–0.83 T, low coercivity of 4.7–8.3 A/m, and high permeability of 5500–18 300 in the frequency range of 1–103 kHz and low magnetostriction between −1.5×10−6 and +10×10−6 including zero. The success in synthesizing the soft magnetic Amorphous Alloys with high stability of supercooled liquid is promising for the future dev...

  • thermal and magnetic properties of fe56co7ni7zr10 xnbxb20 Amorphous Alloys with wide supercooled liquid range
    Materials Transactions Jim, 1997
    Co-Authors: Akihisa Inoue, Tao Zhang, Hisato Koshiba, Akihiro Makino
    Abstract:

    Amorphous Alloys with a wide supercooled liquid region of 45 to 85 K were found to be formed in Fe 56 Co 7 Ni 7 Zr 10-x Nb x B 20 (x= 0 to 10 at%) Alloys by melt spinning. The glass transition temperature (T g ) and the crystallization temperature (T x ) increase by the dissolution of 2 to 4%Nb. The degree of increase is larger for T x than T g , leading to the maximum ΔT,(= T x - T s ) of 85 K for the 2%Nb alloy. The ΔT x value is about 20 K larger than the largest value for the newly developed Fe-(AI, Ga)-(P, C, B, Si) Amorphous Alloys. The crystallization occurs through a single stage, Amorphous→α-Fe+y-Fe+Fe 2 Zr+Fe 16 Nb 6 +B 18 , for the Alloys containing less than about 6%Nb and through two stages, Amorphous→Amorphous+y-Fe→γ-Fe+Co 3 Nb 2 B 5 +Ni g Nb, for the Alloys containing more than 8%Nb. The change in the crystallization process for the Nb-rich Alloys probably reflects the disappearance of Fe 2 (Nb, Zr) precipitates because of the weaker bonding of Fe-Nb pair as compared with Fe-Zr one. As the Nb content increases, the saturation magnetization (I s ) and permeability (μ e ) of the annealed Alloys decrease while the coercive force (H c ) remains almost unchanged. The good soft magnetic properties are obtained for the Alloys containing less than 2%Nb subjected to annealing for 300 s at 800 K and the I s , H c and μ e at 1 kHz are 0.96 T, 2.0 A/m and 19100, respectively, for the 0%Nb alloy and 0.75 T, 1.1 A/m and 25000, respectively, for the 2%Nb alloy. The success of synthesizing the new Amorphous Alloys with a wide supercooled liquid region more than 80 K and with good soft magnetic properties is promising for future development as soft magnetic bulk Amorphous Alloys.

Tsuyoshi Masumoto - One of the best experts on this subject based on the ideXlab platform.

  • light metal base Amorphous Alloys containing lanthanide metal
    Journal of Alloys and Compounds, 1994
    Co-Authors: Tsuyoshi Masumoto
    Abstract:

    Abstract Light-metal base Amorphous Alloys with high specific strength and good corrosion resistance were produced in Al- and Mg-based systems containing lanthanide (Ln) as an essential solute element for glass formation. The Amorphous alloy systems were composed of Al-Ln, Al-Ln-TM, Mg-Ln, Mg-Ca-Ln and Mg-Ln-TM (TM = transition metal). The addition of TM was very effective for the extension of their glass formation ranges. The highest tensile strength (σf) reaches 1250 MPa for the Al-based Alloys and 830 MPa for the Mg-based Alloys. The Mg-based Alloys have a large glass-forming capacity which enables the production of an Amorphous phase by a metallic mold casting method. The extrusion of the Al-based Amorphous powders at temperatures above crystallization temperature caused the formation of high strength materials with finely mixed structure consisting of dispersed intermetallic compounds in an Al matrix. The highest values of σf and the fatigue limit are as high as 940 and 330 MPa, respectively, at room temperature and 520 and 165 MPa at 473 K. The extruded Al-Ni-Mm Alloys have been used as machine parts and subsequent further development as practical materials is expected.

  • ti based Amorphous Alloys with a wide supercooled liquid region
    Materials Letters, 1994
    Co-Authors: Akihisa Inoue, Tao Zhang, Nobuyuki Nishiyama, K Amiya, Tsuyoshi Masumoto
    Abstract:

    Abstract TiCuNiCo quaternary Amorphous Alloys produced by melt spinning were found to have a wide supercooled liquid region before crystallization, though no glass transition was observed in TiCu binary Amorphous Alloys. The largest temperature interval of the supercooled liquid region ( ΔT x ) is as large as 90 K for Ti 50 Cu 25 Ni 20 Co 5 . There is a tendency for ΔT x to increase with an increase in storage modulus and with a decrease in loss modulus. It is therefore presumed that the increase in ΔT x for the multicomponent Amorphous alloy is due to the suppression of crystallization for the supercooled liquid resulting from the increase in viscosity.

L Schultz - One of the best experts on this subject based on the ideXlab platform.

  • relation between short range order and crystallization behavior in zr based Amorphous Alloys
    Applied Physics Letters, 2000
    Co-Authors: L Q Xing, T C Hufnagel, J Eckert, W Loser, L Schultz
    Abstract:

    We have examined the effect of Ti and cooling rate on the crystallization of Zr62−xTixCu20Ni8Al10(0⩽x⩽10) Amorphous Alloys. Ti stabilizes an icosahedral phase in Zr62−xTixCu20Ni8Al10(0⩽x⩽10) Alloys. Without Ti (x=0), crystallization produces cubic and tetragonal intermetallic phases, and the crystallization temperature shows no dependence on the cooling rate at which the Amorphous alloy was produced. The Alloys containing Ti (3⩽x⩽10) precipitate an icosahedral quasicrystalline phase upon annealing, and show a significant reduction of crystallization temperatures with decreasing cooling rates of casting. We propose that the undercooled melts and Amorphous Alloys have icosahedral short-range order. The degree of short-range order or medium-range order in the Amorphous Alloys increases with decreasing cooling rate. Crystallization is easier when the precipitating phase resembles the short-range order of the Amorphous solid. Therefore, the crystallization temperature is reduced when the precipitates are icosa...

  • high strength materials produced by precipitation of icosahedral quasicrystals in bulk zr ti cu ni al Amorphous Alloys
    Applied Physics Letters, 1999
    Co-Authors: L Q Xing, J Eckert, W Loser, L Schultz
    Abstract:

    Zr62−xTixCu20Ni8Al10 (3⩽x⩽5) Amorphous Alloys crystallize via precipitation of icosahedral quasicrystals in the primary crystallization step, leading to nano-sized quasicrystals embedded in an Amorphous matrix. Ti is the decisive component favoring the precipitation of quasicrystals. The mechanical properties of the crystallized Alloys with different amounts of quasicrystalline phase were measured by compression and bending tests. If the volume fraction of quasicrystalline precipitates is below about 50%, the strength increases with an increasing amount of quasicrystalline precipitates, but the ductility does not decrease significantly in comparison with the Amorphous counterpart. The fracture stress reaches 1835 MPa for 50 vol % of quasicrystals. Quasicrystalline precipitates of more than 60 vol % lead to reduction of ductility and strength. This shows a way of producing bulk quasicrystalline materials of high strength by crystallization of bulk Amorphous Alloys.

  • mechanically alloyed zr ti cu ni Amorphous Alloys with significant supercooled liquid region
    Materials Letters, 1995
    Co-Authors: M Seidel, J Eckert, L Schultz
    Abstract:

    Quaternary Zr-Ti-Cu-Ni Amorphous Alloys have been prepared by mechanical alloying from crystalline elemental powders and investigated by X-ray diffraction and differential scanning calorimetry (DSC). The Amorphous Alloys were found to exhibit a wide supercooled liquid region before crystallization. This is believed to be the first evidence for the appearance of a supercooled liquid region for mechanically alloyed Zr-Ti-based Amorphous powders. The transformation to the crystalline state has been followed by isothermal and constant-rate heating DSC. The origin of the significant supercooled liquid region of these new Alloys is discussed.