Gas atomization으로 제조된 Ti_50Ni_30Cu_20 합금 분말의 상변태 거동

Abstract

For the fabrication of bulk near-net-shape Ti-Ni-Cu shape memory alloys, consolidation of Ti-Ni-Cu alloy powders are useful because of their brittle property. In the present study, Ti_50Ni_30Cu_20 shape memory alloy powders were prepared by gas atomization and martensitic transformation temperatures and microstructures of those powders were investigated as a function of powder size. The size distribution of the powders was measured by conventional sieving, and sieved powders with the specific size range of 25 to 150 μm were chosen for this examination. XRD analysis showed that the B2-B19 martensitic transformation occurred in the powders. In DSC curves of the as-atomized Ti_50Ni_30Cu_20 powders as a function of powder size, only one clear peak was found on each cooling and heating curve. The martensitic transformation start temperature(M_s) of the 25-50 μm powders was 31.5℃. The M_s increased with increasing powder size and the difference of M_s between 25-50 μm powders and 100-150 μm powders is only 1℃. The typical microstructure of the rapidly solidified powders showed cellular morphology and very small pores were observed in intercellular regions.