REVERSIBLE SHAPE MEMORY EFFECT IN A BETA-1 CU-ZN ALLOY CONTAINING ALPHA-PRECIPITATES

The beta //1 phase of Cu-Zn alloys containing alpha precipitates of 20-40% in the volume fraction exhibits a remarkable reversible shape memory effect (RSM) on cooling and heating between room temperature and minus 196 degree C after deformation at minus 196 degree C below the Ms temperature. The role of the alpha precipitates in the RSM was examined by optical and electron microscopy, electrical resistance measurements and tensile tests between room temperature and minus 196 degree C. It is concluded that the stress concentration by the dislocation pile-ups induces particular variants of martensite in the beta //1 crystals at low temperature, and that these martensite crystals cause a spontaneous shape change of the material upon cooling.