On the effect of TiC particles on the tensile properties and on the intrinsic two way effect of NiTi shape memory alloys produced by powder metallurgy

The present study investigates the tensile properties of a nickel titanium (NiTi) shape memory alloy (SMA) produced by powder metallurgy (PM) with and without TiC-particles. It discusses the effect of the addition of particles on the mechanical behavior in tension and studies the intrinsic two way effect (epsilon(2W)) after thermomechanical training. Special emphasis is placed on the stability of epsilon(2W) after subsequent thermal cycling. The results are discussed on the basis of an analysis of the thermomechanical data and microstructural results. The present study shows that the PM route can produce NiTi SMAs with tensile properties which match those of materials produced by classical ingot metallurgy. Adding TiC particles to NiTi SMAs alters the phase transition temperatures (PTTs) and affects the SMA performance. Adding more than ten volume percent TiC particles results in early and brittle rupture during tensile loading. (C) 1999 Published by Elsevier Science S.A. All rights reserved.