Cu-Zn-Al形状記憶合金の結晶粒微細化による機械的性質および形状記憶熱エンジンの性能に及ぼす結晶粒径の影響

概要

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The effect of grain size on the mechanical properties of the grain-refined Cu-Zn-Al shape-memory alloys was investigated by DSC, tensile testing and shape-memory heat engine drive testing. It was found that the β-grain size of the alloys at a constant heat-treatment time of 5 minutes varies from 37μm to 800μm depending on the alloying elements: Ni, Fe, V and Co. In addition, the β-grain size of each alloy depends on the solution treatment time itself. The transformation heat obtained by DSC measurements increased with an increase in grain size. The influence of the grain size on the mechanical properties was investigated by tensile testing. It was found that the 0.2 % proof stress of both the β-phase and M-phase state alloys changes in accordance with the Hall-Petch relation. The ultimate tensile stress and fracture strain of the specimens solution-treated up to 20 minutes change slightly. While those of the specimens solution-treated for 40 minutes decrease considerably. In order to test the effect of grain sizes on the heat engine, an off-set-crank-type heat engine is equipped with shape-memory-alloy springs for durable cycle testing. Using a similar lot sample but different solution treatment times, the durable cycles of the heat engine increase with smaller grain size. Using a similar solution treatment time but different grain sizes, the durable cycles of the heat engine increase with smaller grain size.
1990-12-25