熱エンジン用形状記憶合金素子の形状記憶・機械的特性に及ぼす加熱冷却サイクルの影響

抄録

Since Ti-Ni shape memory alloys(SMAs) work well at temperature less than 373K ,SMAs are expect to apply the heat-engine which recovers low temperature thermal energy .The pulley-type SMA heat-engine, which is one of the SMA heat-engine, is driven by heating and cooling of the liner or coil shape SMA element. We fabricated tape-shaped SMA elements for the purpose of improving the product's life span. However, shape memory and mechanical characteristics of tape-shaped SMA are deteriorated with increasing number of heating/cooling cycle. In this study, the effects of heating/cooling cycle on the shape memory and mechanical characteristics of tape-shaped SMA element are investigated. The chemical composition of the specimen is Ti-45.0Ni-5.0Cu(at%), heat treatment condition is 673K for 3.6ks and the specimen is memorized two kinds of curvature shape φ10 and φ15. The thermal cycles vary from 0 to 105 times. Recovery bending force of each specimens tend to decrease with increase in the number of thermal cycles. This tendency is caused by increase of the volume fraction of residual martensite with increase in the number of thermal cycles. However, recovery bending force of φ10 curvature-shaped specimen decrease faster than that of φ15 curvature-shaped specimen because φ10 curvature-shaped specimen is applied more bending deformation.