Effect of annealing temperature on martensitic transformation of Ti49.2Ni50.8 alloy processed by equal channel angular pressing
(1. Key Laboratory of Superlight Material and Surface Technology, Ministry of Education,
Harbin Engineering University, Harbin 150001, China;
2. Center for Biomedical Materials and Engineering, College of Materials Science and Chemical Engineering,
Harbin Engineering University, Harbin 150001, China;
3. Department of Materials Science and Engineering, College of Engineering,
Peking University, Beijing 100871, China;
4. Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000, Russia)
Harbin Engineering University, Harbin 150001, China;
2. Center for Biomedical Materials and Engineering, College of Materials Science and Chemical Engineering,
Harbin Engineering University, Harbin 150001, China;
3. Department of Materials Science and Engineering, College of Engineering,
Peking University, Beijing 100871, China;
4. Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, Ufa 450000, Russia)
Abstract: The effect of annealing temperature on the martensitic transformation of a Ti49.2Ni50.8 alloy processed by equal channel angular pressing (ECAP) was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The as-ECAP processed and subsequently annealed Ti49.2Ni50.8 alloys consist of B2 parent phase, Ti4Ni2O phase and B19′ martensite at room temperature. Upon cooling, all samples show B2→R→B19′ two-stage transformation. Upon heating, when the annealing temperature is less than 400 °C, the samples show B19′→R→B2 two-stage transformation; when the annealing temperature is higher than 500 °C, the samples show B19′→B2 single-stage transformation. The B2-R transformation is characterized by wide interval due to the dislocations introduced during ECAP.
Key words: TiNi alloy; equal channel angular pressing; martensitic transformation; annealing temperature