Enhanced internal friction and specific strength of porous TiNi shape memory alloy composite by the synergistic effect of pore and Ti2Ni

Abstract

The contradictory relationship between the damping capacity and specific strength remains a challenge for developing metallic damping materials with high strength and stability for energy-absorbing and energy-saving applications. Porous TiNi shape memory alloy composite (SMAC) seems to be a valid strategy to solve this problem. The deformation and damping behaviors of porous SMAC (composed on a particle-like brittle Ti2Ni embedded in ductile TiNi shape memory alloy matrices) were studied and precisely determined using dynamic mechanical analyzer (DMA) and compressive testing in this study. The porous B2–TiNi and Ti2Ni composites exhibit a three-stage deformation character while only one-yielding phenomenon in the compressive stress-strain curves, which is ascribed to the synergistic effect of pore together with the interaction of TiNi and Ti2Ni phases which is different from dense SMAC. This is because porous SMAC with 37% porosity demonstrates exceptional damping property of at least 0.025 at relatively low strain amplitude in −100 to 200 °C temperature range, which resulted from modulus mismatch and the massive interfaces between pore/matrix and TiNi/Ti2Ni. Moreover, the high 113 MPa∙cm3/g compressive specific strength and 27% fracture strain in RT to 130 °C temperature range further dominate on dense SMAC.