Ways to lower transformation temperatures of porous NiTi shape memory alloy fabricated by self-propagating high-temperature synthesis

Self-propagating high-temperature synthesis (SHS) of porous NiTi alloy for hard tissue implants shows shape memory effect and superelasticity due to the B2 ↔ B19′ transformation. In order to decrease the Af temperature to the human body temperature, 310 K, the effects of preheating temperature, thermal cycling and the third element Mo on the transformation temperatures were investigated using differential scanning calorimetry. The experimental results indicate that the preheating temperature has no obvious effect on the transformation temperatures; the transformation temperatures slightly decreased with increasing number of thermal cycles, but the Af temperature was still above 310 K within 10 times; the addition of Mo decreased transformation temperatures considerably, and the R-phase transformation was induced during cooling. Transformation temperatures of porous TiNi(Mo) shape memory alloys with appropriate Mo contents fabricated by SHS meet the demands for human-body implants.