INTERFACIAL STUDIES OF UNCOATED AND COATED NITI PARTICLES IN SNPBAG MATRIX

Uncoated and copper electroless coated fine NiTi superelastic particle s have been incorporated into liquid SnPbAg matrix. The wettability of the Cu coating by the molten alloy was determined with a wetting bala nce. The composite interfaces have been investigated by Auger Spectros copy. Uncoated NiTi reacted with the matrix to form Ni-Sn intermetalli cs, whereas the Cu layer of coated particles behaved as a sacrificial layer, leading to a small interfacial zone containing neither Cu-Sn no r Ni-Sn intermetallics. The mechanical characterisation of Cu-coated N iTi/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 in terms of t he superelastic properties of the NiTi SMA particles.