Papers by Author: Mikio Fukuhara

Abstract: Large-size Ni-based bulk metallic glass (BMG) composite samples exhibiting simultaneously high strength, enhanced plasticity and improved conductivity were produced by spark plasma sintering of mixed glassy powder blended with high-conductive Cu particulates. This opens new possibilities for the applications of the BMG composites as functional and structural materials.

Abstract: We investigated consolidation behavior of gas-atomized Cu50Zr45Al5 metallic glassy alloy powders by a spark plasma sintering (SPS) process. Density of the sintered samples increased with an increase in sintering temperature. The nearly full density samples without crystallization could be attained by the SPS process at sintering temperature of 693 K under pressure of 600 MPa. The produced samples exhibited high-strength and met large-size requirement. The SPS process makes it possible to fabricate the large-size bulk metallic glasses without limitation of dimensions and alloy system.

Abstract: Although a Ti47.4Zr5.3Ni5.3Cu42 glassy alloy does not occur precipitation of crystalline in annealing of prolonged time below glass transition temperature, it shows slightly embrittlement during passing through devitrification process. The embrittlment behavior may be connected to structural relaxation. Using ultrasonic, in this study, acoustic characteristics of the glassy alloy during progressive devitrification were examined in terms of structural relaxation. The structural changes are characterized by decreases in specific volume, bulk modulus, Lamè parameter and Poisson ratio, accompanied by structural relaxation.

Abstract: Using ultrasonics, acoustic characteristics of Pd40Cu30P20, Zr55Cu30Al10Ni5, Zr65Pd12.5Ni10Al7.5 Cu5, Cu55Zr30Ti10Pd5, Cu45Zr20Hf25Ag10 and Ti41.5Cu42.5Ni7.5Hf5Zr2.5Sn1 glassy alloys were examined in terms of complex elasticity. The order of bulk modulus (K), Lamè parameter (λ ), Young (E ) and shear (G ) moduli of the glassy alloys is monopoltical character of glassy alloys, except for polymers and rubbers. For metals and alloys, ceramics, polymers and glassy alloys, Poison’s ratio correlates well to ratio G /K. Complex elasticity indicates that viscoelasticity of the glassy alloys is predominated by volumetric motion.