In this study,the effect of triple-cycling heat treatment on the microstructure,phase,and compression behaviour of directed energy deposited(DED)Ti-7Mo alloy was investigated with a focus on a non-equilibrium to equil...In this study,the effect of triple-cycling heat treatment on the microstructure,phase,and compression behaviour of directed energy deposited(DED)Ti-7Mo alloy was investigated with a focus on a non-equilibrium to equilibrium microstructure transition.As a result of thermal accumulation,in situ cycling,and rapid solidification,the as-deposited sample presents a continuous gradient microstructure withα-Ti in the top region andα+βin the bottom region.After the triple-cycling heat treatment,theα+βTi at the bottom region,which is non-equilibrium,changes to a state of equilibrium nearα-Ti.Meanwhile,the microstructure becomes more uniform throughout the entire sample.The morphology of theα-Ti phase changes from acicular to a short rode-like shape with increases in the number of dimensions.In terms of the mechanical properties,both the microhardness and compression properties were improved,particularly with respect to the fracture characteristics.The heat-treated sample possesses a much higher ductility than the brittle fractural behaviour.This work provides new insights into the microstructure and property optimisation and homogenisation of DED-processed Ti-based components with cycling heat treatment.展开更多
基金This work was supported by the National Key R&D Program of China(Grant No.2016YFB1100100)Fundamental Research Funds for the Central Universities(Grant No.31020180QD130)Production-Education-Research program of Aero Engine Corporation of China(Grant No.HFZL2019CXY019).
文摘In this study,the effect of triple-cycling heat treatment on the microstructure,phase,and compression behaviour of directed energy deposited(DED)Ti-7Mo alloy was investigated with a focus on a non-equilibrium to equilibrium microstructure transition.As a result of thermal accumulation,in situ cycling,and rapid solidification,the as-deposited sample presents a continuous gradient microstructure withα-Ti in the top region andα+βin the bottom region.After the triple-cycling heat treatment,theα+βTi at the bottom region,which is non-equilibrium,changes to a state of equilibrium nearα-Ti.Meanwhile,the microstructure becomes more uniform throughout the entire sample.The morphology of theα-Ti phase changes from acicular to a short rode-like shape with increases in the number of dimensions.In terms of the mechanical properties,both the microhardness and compression properties were improved,particularly with respect to the fracture characteristics.The heat-treated sample possesses a much higher ductility than the brittle fractural behaviour.This work provides new insights into the microstructure and property optimisation and homogenisation of DED-processed Ti-based components with cycling heat treatment.
