Ti₃Sn–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 Ti3Sn–NiTi syntactic foams using Ti58Ni34Sn8 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 Ti3Sn/NiTi eutectic with an interspacing distance of 600–900 nm and a Ti2Ni 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 cm3/g) at a wide temperature range because of the large interfacial area and good lattice strain matching in the lamellar Ti3Sn/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 Ti3Sn–NiTi syntactic foams showed the highest comprehensive coefficient, (σ/ρ)·tan δ, of 5.07 to date. Because of these impressive features, Ti3Sn–NiTi syntactic foams become a promising material for energy absorption and damping applications.