Gradient porosity and large pore size NiTi shape memory alloys

Porous NiTi alloys with gradient porosity and large pore size were successfully fabricated by using a temporary space-holder (NH4HCO3) and a conventional sintering method. The pore characteristics of the porous alloys can be tailored effectively by changing the amount of NH4HCO3 added, and the use of NH4HCO3 has no influence on the microstructure and phase transformation behavior of the porous alloys. The fabricated samples with radial gradient porosity exhibit excellent superelasticity (higher than 4%).