Distribution and evolution of low-energy twin boundary density in time-space domain during isothermal compression for Ni80A superalloy
(1. Chongqing Key Laboratory of Advanced Mold Intelligent Manufacturing, College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China;
3. Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China)
2. State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China;
3. Collaborative Innovation Center of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China)
Abstract: Adjusting the density of low-energy boundary, i.e., Σ3n twin boundary, in a thermal-plastic deformation process is a significant approach to enhance grain boundary-related properties for an alloy. In order to uncover the distribution and evolution of twin boundary density in a current-heating forming process, and their inner mechanisms dependent on grain size and stored-energy, an electrical-thermal-mechanical multi-field coupling and macro-micro multi-scale coupling finite element model was established. Simulation results of isothermal compression processes for Ni80A superalloy show that twin-boundary density keeps constant in the heating and holding stages, while it increases quickly and then intends to decrease in the compressing stage. Its distribution gets more homogeneous under high temperature and medium strain rate. The processing parameter domains corresponding to finer grain size and higher stored-energy, as well as higher dynamic recrystallization degree, contribute to promoting the twin boundary density.
Key words: Σ3n twin boundary; multi-scale coupling simulation; current-heating forming; nickel-based superalloy