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

Uncoated and copper electroless coated fine NiTi superelastic particles hav e been incorporated into a liquid SnPbAg matrix. The wettability of the Cu coating by the molten alloy was determined with a wetting balance. The comp osite interfaces have been investigated by Auger electron spectroscopy (AES ). Uncoated NiTi reacted with the matrix to form Ni-Sn intermetallics, wher eas the Cu layer of coated particles behaved as a sacrificial layer, leadin g to a small interfacial zone containing neither Cu-Sn nor Ni-Sn intermetal lics. The mechanical characterisation of Cu-coated NiTi/SnPbAg composites s hows a reinforcement of the composite material compared to the monolithic m atrix. and also an unusual increase of the elongation at rupture. These res ults can be interpreted with the superelastic properties of the NiTi shape memory alloy (SMA) particles. (C) 1999 Elsevier Science S.A. All rights res erved.