电子束增材制造技术用Ti-Ni预合金粉末性能研究

The investigation of Ti-Ni Pre-alloyed Powder Used for Electron Beam Melting

摘要:

采用DSC、SEM 和XRD等测试手段研究和分析了电子束增材制造（EBM）技术用53~106 μm Ti-Ni预合金粉末的性能及其随热处理温度和热循环次数的变化规律。结果表明：预合金粉末粒度呈正态分布，粉末内部填充及球形度良好，适于EBM打印使用；随热处理温度的升高预合金粉末相组成不发生变化但组织和成分变得均匀，内应力和位错被消除，晶粒尺寸长大，使得其550 oC热处理后加热和冷却过程由多步相变转变为单步相变，650 oC热处理后相变点开始保持稳定，而750 oC热处理后达到最佳微烧结状态；预合金粉末在750 oC烧结热循环和保温过程中相组成、单步相变行为和相变点均不发生变化，具有良好的热循环稳定性；底板及粉末层采用750 oC预热温度成功制备出表面状态良好的Ti-Ni合金实体样品。

Abstract:

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 53~106μm Ti-Ni pre-alloyed powder used for electron beam melting (EBM) were studied using the differential scanning calorimeter, X-ray diffraction, scanning electron microscope. The results showed that the powder had good particle size distribution, internal filling and spherical topography, and suitable for EBM process. The structure and composition became uniform, internal stress and dislocation were eliminated and crystal grain size grown with the increase of heat treatment temperature, which caused the original multi-step phase transformation to one-step phase transformation during the heating and cooling process after 550 °C and the phase transformation points maintains a stable state after 650 °C. The phase composition not changed during the heat treatment process and the powder had best sintered state under 750 °C. The phase composition, one-step phase transformation behavior and phase transformation points were all not changed for the powder during 750 °C thermal cycles test, showed good thermal cycling stability. Ti-Ni solid samples with good surface condition were successfully prepared using EBM under 750 °C preheating temperature for bottom plate and powder layer.