The use of shape memory alloy NiTi particles in SnPbAg matrix: interfacial chemical analysis and mechanical characterisation

Uncoated and copper electroless coated fine NiTi superelastic particles have been incorporated into a liquid SnPbAg matrix. The wettability of the Cu coating by the molten alloy was determined with a wetting balance. The composite interfaces have been investigated by Auger electron spectroscopy (AES). Uncoated NiTi reacted with the matrix to form Ni–Sn intermetallics, whereas the Cu layer of coated particles behaved as a sacrificial layer, leading to a small interfacial zone containing neither Cu–Sn nor Ni–Sn intermetallics. The mechanical characterisation of Cu-coated NiTi/SnPbAg composites shows a reinforcement of the composite material compared to the monolithic matrix, and also an unusual increase of the elongation at rupture. These results can be interpreted with the superelastic properties of the NiTi shape memory alloy (SMA) particles.