TiSn-NiTi Syntactic Foams with Extremely High Specific Strength and Damping Capacity Fabricated by Pressure Melt Infiltration.

NiTi shape-memory alloy foams have attracted much attention due to their unique superelasticity, excellent mechanical properties, and damping capacities, but their high-temperature damping capacity and compressive strength remain to be a challenge. Herein, we demonstrate the preparation of TiSn-NiTi syntactic foams using TiNiSn alloy and alumina microspheres by novel pressure melt infiltration and air-cooling strategies. The syntactic foams with 45% porosity contain spherical and well-distributed pores of average size 500-600 μm. A fine lamellar TiSn/NiTi eutectic with an interspacing distance of 600-900 nm and a TiNi interfacial layer of 10 μm thickness were formed between the alumina microspheres and the matrix. The syntactic foams achieved a high specific compressive strength (110.2-110.8 MPa cm/g) at a wide temperature range because of the large interfacial area and good lattice strain matching in the lamellar TiSn/NiTi. They also exhibited 2% recoverable strain and high specific energy absorption capacity (31.5 kJ/kg). Moreover, the foams showed ultrahigh damping capacity (0.066) at a temperature range of -150 to 200 °C. Most interestingly, the TiSn-NiTi syntactic foams showed the highest comprehensive coefficient, (σ/ρ)·tan δ, of 5.07 to date. Because of these impressive features, TiSn-NiTi syntactic foams become a promising material for energy absorption and damping applications.