Synthesis of new bulk metallic glassy Ti 60 Al 15 Cu 10 W 10 Ni 5 alloy by hot-pressing the mechanically alloyed powders
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TALLIC glassy alloys are solid, consisting of metallic atoms arranged in random manner with no obvious long-range order. Due to their unusual superior chemical, physical, and mechanical properties,[1,2,3] metallic glasses have received great attention as promising high-tech materials. Although rapid solidification and casting techniques are successfully used for preparing this class of advanced materials, they are not capable of fabricating those systems that have high melting points or poor glass-forming ability. The mechanical alloying (MA) method has introduced a practical technique for preparing large amounts of the glassy alloy powders that cannot be obtained by traditional methods of fabrication.[4,5] However, Ti-base bulk metallic glasses (BMGs) reveal a very high fracture strength of about 2.2 GPa; it shows a low modulus of elasticity, being in the range of 80 GPa.[6] He et al.[7] have shown that the Young’s modulus of metallic matrix of cast Ti-base glassy alloy can be improved to show higher values when reinforced with crystalline Mo. In the present work, MA technique using a low-energy ball mill was employed to fabricate new multicomponent Ti60Al15Cu10W10Ni5 glassy alloy powders that were expected to M. SHERIF El-ESKANDARANY, Permanent Professor of Materials Science and Metallurgy, Faculty of Engineering, Al-Azhar University, Cairo, Egypt, used to work at Inoue Superliquid Glass Project, Exploratory Research for Advanced Technology, Japan Science and Technology Corporation, Yagiyama-minami, 2-1-1, Sendai 982-0807, Japan, and is now the Vice-President of Academy of Scientific Research & Technology for Technology Development & Scientific Services Sector, Ministry of Scientific Research, Cairo 11516, Egypt. Contact e-mail: msherif99@yahoo. com or [email protected] A. INOUE, Professor and Dean, is with the Institute for Materials Research, Tohoku University, Katahira 2-11, Sendai 980-8577, Japan. Manuscript received July 3, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
have excellent mechanical properties. The existence of the supercooled liquid region in the fabricated glassy alloy powders adds an important dimension to get a successful consolidation step, using a proper consolidation method.[8] The effects of the hot-pressing temperature on the density and microhardness of the consolidated powders are discussed. Finally, we propose a combination process of MA plus hot-pressing for forming large amounts of fully dense BMG alloy that shows superior mechanical properties. II.
EXPERIMENTAL PROCEDURE
Pure elemental powders (99.9 pct or better) of Ti (70 mm), Al (10 mm), Cu (10 mm), Ni (25 mm), and W (50 mm) were balanced to give the desired nominal composition (at. pct) of Ti60Al15Cu10W10Ni5 and mixed in a glove box under an argon (99.999 pct) atmosphere. The mixed powders of the starting reactant materials were then sealed into a tempered chromium steel vial (1,000 mL in volume), together with 50 tempered chromium steel balls (14 mm in diameter) in the glove box. A ball-to-powder weight ratio of 30:1 w
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