Martensitic Transformation of NiTi and NiTi-TiC Composites

¹ Advanced Composite Materials Engineering, PSE-EPFL, 1015 Lausanne, Switzerland
² Institut de Génie Atomique, EPFL, 1015 Lausanne, Switzerland
³ Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge MA 02139, U.S.A.

Abstract

Calorimetry and internal friction were used to study the martensitic phase transformation of shape-memory metal matrix composites consisting of nearly equiatomic NiTi with up to 20 vol.% TiC particles. The start and final temperatures for the austenite-martensite transformation (M_s, M_f) and martensite-austenite transformation (A_s, A_f) are lower when measured by internal friction than when measured by calorimetry. In composites, TiC particles lower M_f and A_sbut do not affect M_sand A_f. It is concluded that dissipative work due to twinning takes place to accommodate internal stresses.