High damping capacity in porous NiTi alloy with bimodal pore architecture

Abstract Porous NiTi exhibits pseudoelasticity, shape memory and low modulus, and thus shows application potential as high damping and bio-materials. Here Ni 50.5 Ti 49.5 foam with bimodal pore structure was prepared by elemental powder sintering and high damping capacity demonstrated. NaCl particles of 500–600 μm and 75–90 μm diameters were adopted as space holder to create large and small pores with porosity of 40%. Incomplete densification of NiTi alloy created even smaller pores of 10–50 μm and contributed another 21.47% porosity. This NiTi foam containing bimodal pores has a compressive modulus of 1.83 GPa, smaller than that of foam with single pores or estimation by Gibson–Ashby model. This low modulus is attributed to the stress-induced martensite transformation under compressive load. The foam exhibits high damping capacities during phase transformation and at austenite region because of deformation, dislocation motion in thin nodes/walls and stress-induced martensite formation.