Structure and martensitic transformation of NiTi-TiC composite
Tomasz Goryczka, Barbara Szaraniec, Józef Lelątko
Quarterly No. 1, 2010 pages 30-34
DOI:
keywords: composite NiTi-TiC, sintering, martensitic transformation, NiTi alloy
abstract Composite NiTi-TiC was produced by use of powder metallurgy, with addition of titanium carbide: 0, 3 and 5 wt. % Analysis of chemical composition revealed homogeneity of nickel and titanium element distribution in composite matrix - negligible differences in element contents was stated. Phase identification, which was carried out with use of electron back scatter diffraction, showed that TiC particles were surrounded by equilibrium Ti2Ni phase. This phase does not take part in the martensitic transformation. The rest of the composite matrix consisted of the B19’ martensite. The composite matrix transformed to the parent phase in one step. Moreover, the martensitic transformation occurred as a reversible one. Addition of titanium carbide in amount up to 5% did not influenced course of the martensitic transformation as well as its transformation temperatures. Thermal cycling of the composites leaded to decrease of the transformation temperatures and enthalpy. It might be due to the presence of local stress caused by TiC particles and/or reaction between dislocations and martensitic plates. The TiC particles can occur as an obstacle for martnesitic plates. In results of that lowering temperature is required to complete transformation. The transformation stabilizes after 20 thermal cycles.