Prediction of precipitate evolution and martensite transformation in Ti-Ni-Cu shape memory alloys by computational thermodynamics

3rd International Conference on Competitive Materials and Technology Processes

Povoden-Karadeniz, A.^1 ; Cirstea, D.C.^2 ; Kozeschnik, E.^1

Vienna University of Technology, Institute of Materials Science and Technology, Vienna, Austria^1

National Institute for Research and Development in Electrical Engineering, INCDIE ICPE-CA, Advanced Materials Department, Bucharest, Romania^2

关键词: Computational thermodynamics;    Intermetallic precipitates;    Martensite start temperature;    Martensite transformations;    Shape memory alloys(SMA);    Solid state transformations;    Ti-ni-cu shape memory alloys;    Time-temperature-precipitation;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/123/1/012038/pdf
DOI  :  10.1088/1757-899X/123/1/012038

来源: IOP

【 摘 要 】

Ti-50Ni to Ti-55Ni (at.%) can be termed as the pioneer of shape memory alloys (SMA). Intermetallic precipitates play an important role for strengthening. Their influence on the start temperature of the martensitic transformation is a crucial property for the shape memory effect. Efforts for increasing the martensite start temperature include replacement of a part of Ni atoms by Cu. The influence of Cu-addition to Ti-Ni SMA on T0- temperatures and the character of the austenite-martensite transformation is evaluated using a new thermodynamic database for the Ti-Ni-system extended by Cu. Trends of precipitation of intermetallic phases are simulated by combining the assessed thermodynamics of the Ti-Ni-Cu system with assessed diffusion mobility data and kinetic models, as implemented in the solid-state transformation software MatCalc and are presented in the form of time-temperature-precipitation diagrams. Thermodynamic equilibrium considerations, complemented by predictive thermo-kinetic precipitation simulation, facilitates SMA alloy design and definition of optimized aging conditions.