电子束增材制造技术用Ti-Ni预合金粉末性能研究

The properties of pre-alloyed powder have an important influence on the additive manufacturing process, especially for Ti-Ni alloys with special shape memory effects. However, there are limited reports on the studies for the variation of Ti-Ni pre-alloyed powder with heat treatment temperatures and number of thermal cycles. In this work, the phase transformation behavior, microstructure and phase composition of 53~106 μm Ti-Ni pre-alloyed powder used for electron beam melting (EBM) were studied using the differential scanning calorimeter, X-ray diffraction, and scanning electron microscope. The results show that the powder has good particle size distribution, internal filling and spherical topography, and suitable for EBM process. The structure and composition become uniform, internal stress and dislocation are eliminated and crystal grain size grows with the increase of heat treatment temperature, which causes the original multi-step phase transformation to one-step phase transformation during the heating and cooling process after 550℃ and the phase transformation points maintain a stable state after 650℃ heat treatment. The phase composition is not changed during the heat treatment process and the powder has best sintering state at 750℃. The phase composition, one-step phase transformation behavior and phase transformation points are all not changed for the powder during 750℃ thermal cycles test, indicating good thermal cycling stability. Ti-Ni solid samples with good surface condition are successfully prepared under 750℃ preheating temperature for bottom plate and powder layer.