Shape memory characteristics of highly porous Ti-rich TiNi alloys

• Transformation temperatures of TiNi fibers were increased by rapid solidification.
• Porous TiNi bulks with 75% porosity could be prepared by solid state sintering.
• Residual strain of porous TiNi bulks was recovered more than 80%.
• Small elastic modulus of 3.03 GPa could be obtained because of high porosity.

AbstactTi50.5Ni49.5 alloy fibers were fabricated using a melt overflow process. The effects of rapid solidification on the microstructure, transformation temperatures, and shape memory characteristics of Ti-rich TiNi alloys were investigated. The addition of 0.5 at% Ni in Ti50Ni50 alloy increased the transformation temperatures. Highly porous billets were produced using a vacuum sintering technology with the fibers. While compression mechanical testing carried out on porous specimens revealed the residual strain of 6.7%, this strain recovered up to 5.4% due to the shape memory effect. The permanent plastic strain resulting from 10% compressive deformation was only 1.3% in the TiNi shape memory alloy with 75% porosity. Because of the high porosity of sintered specimens, an elastic modulus of about 3.03 GPa could also be obtained.

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