ELECTRIC RESISTANCE PHENOMENA IN POROUS Ni-Ti SHAPE-MEMORY ALLOYS PRODUCED BY SHS

摘要

The transformation behavior, especially the electric resistance versus temperature, of porous Ni-Ti SMAs produced by SHS is studied comprehensively for the first time. It is found that the transformation temperatures of porous Ni-Ti SMAs with different porosity are almost identical, and the latent heats of transformation increase with increasing porosity. The electric resistance-temperature curves of porous Ni-Ti SMAs produced by SHS are very novel and different from those of cast Ni-Ti SMAs prepared by conventional arc-melting method or those of dense Ni-Ti SMAs prepared by powder metallurgy. There appear two peaks in the cooling process while no peak is observed in the heating process in the electric resistance-temperature curves. Furthermore, the expansion/shrinkage of porous Ni-Ti SMAs produced by SHS during cooling/heating is relatively small.