Martensitic Transformation of NiTi and NiTi-TiC Composites
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.
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 (Ms, Mf) and martensite-austenite transformation (As, Af) are lower when measured by internal friction than when measured by calorimetry. In composites, TiC particles lower Mf and Asbut do not affect Msand Af. It is concluded that dissipative work due to twinning takes place to accommodate internal stresses.
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