• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.304-308
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• 2002

The new Cu-Zr-Ti-Ni-Pd amorphous alloy system has been introduced and manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties of the alloys were examined. The reduced glass transition temperature(Trg = Tg/Tm) and the supercooled liquid region(${\Delta}$Tx = Tx-Tg) of $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ alloy were 0.620 and 57 K respectively. $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ amorphous alloy was produced in the rod shape with 2mm diameter using the Cu-mold die casting. The hardness value of the amorphous bulk alloy was 432 DPN.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.288-292
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• 2002

Ni-base amorphous alloys were manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties were examined. The reduced glass transition temperature and the supercooled liquid region of $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$alloy were 0.621 and 46 K respectively. $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$ alloy was produced in the rod shape 3mm diameter using the Cu-mold die casting. Hardness, compression strength, elongation and elastic modulus of the alloy were 850 DPN, 2.75 GPa, 1.8% and 150 GPa respectively. Moreover, compression strength of 2.75 GPa was the highest value in the amorphous bulk alloy produced up to now.

• Journal of Korea Foundry Society
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• v.26 no.5
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• pp.227-231
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• 2006

Liquid formability of bulk amorphous alloys is known to be very poor due to their high viscosity comparing with conventional metallic materials. It is important to have the fabricating technology of bulk amorphous alloys in order to make the components with complicated shape. Liquid formability includes the mold cavity filling ability and the hot tear(crack) resistance during solidification. A mold made of a commercial tool steel for the formability test was designed. Melting was performed by the arc melting furnace with melting capacity of 200 g in an argon atmosphere. Liquid formability and glass forming ability of Cu base and Ni base bulk amorphous alloys were measured and evaluated. Mold filling ability of Ni-Zr-Ti-Si-Sn alloy was better than that of Cu-Ni-Zr-Ti alloy, however the reverse is the hot tear resistance. Bulk amorphous alloy is very susceptible to crack if partial crystallization occurs during solidification. Crack resistance was thought to be closely related with the glass forming ability.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.215-217
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• 2008

Crystallization behavior of the bulk metallic glass (BMG) during compression and tension was studied in the supercooled liquid region (SLR). Rod samples of the BMG alloy were produced by consolidating gas atomized powders of $Cu_{54}Zr_{22}Ti_{18}Ni_6$ using spark plasma sintering. The crystallization behavior in these samples was examined by tackling changes in thermal property during heating the samples in DSC. The present BMG alloy was firstly decomposed and then crystallized during annealing in the SLR. The phase decomposition from the original amorphous phase was retarded by the compressive stress, while it was accelerated by the tensile stress.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.281-284
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• 2005

Room and high temperature deformation behaviors of Cu-Zr-Ti-Pd bulk metallic glasses produced by copper mold casting were investigated. The addition of Pd was shown to enhance the glass forming ability and thermal stability of Cu-Zr-Ti base bulk metallic glass. The compressive strength of $Cu_{55}Zr_{30}Ti_{10}Pd_5$ bulk metallic glass was 2230 MPa with 1.8 plastic strain. The stress overshoot and yield drop phenomenon were observed below $487^{\circ}C$ and a drastic decrease in the flow stress was observed at $487^{\circ}C$. The stress overshoot is thought to be associated with stress-induced structural relaxation.