粉末冶金TA7 ELI合金的制备及其界面反应层

Preparation of powder metallurgy TA7 ELI alloy and its interface reaction layer

采用Ti-5A1-2.5Sn ELI(TA7 ELI)洁净预合金粉末通过热等静压(HIP)致密化工艺制备TA7 ELI合金。利用粒度仪和扫描电镜等对粉末的粒径分布、形貌和化学成分进行表征。利用金相显微镜分析热等静压后TA7 ELI合金的显微组织,利用电子探针分析包套和粉末反应层的元素分布。结果表明:粉末的平均粒度约为80μm,形貌呈球形;经1000℃、130 MPa、3 h热等静压后,材料的相对密度达到理论密度的99.5%,获得平均晶粒直径约为40μm的细小等轴晶组织;包套与TA7 ELI粉末界面反应层厚度为3～8μm,反应层富集Al和Sn元素,Fe元素沿TA7 ELI晶界快速扩散,在界面附近呈网状分布。

The TA7 ELI alloy was prepared by hot isostatic pressing （HIP） of high purity pre-alloyed powders using powder metallurgy Ti-5Al-2.5Sn ELI alloy. The grain size distribution, morphology and chemical component of the powders were investigated by particle analyzer and scanning electron microscopy （SEM）. The microstructures of TA7 ELI sample after HIP were observed by optical microscopy （OP）, and the diffusion layer between container and powders was analyzed by electron probe micro-analyzer （EPMA）. The results indicate that the medium diameter of powder is about 80 μm, and the powders are nearly spherical. The relative density of powder material is over 99.5% after HIP at 1 000 ℃ and 130 MPa for 3 h.The fine equiaxed grain microstructure is obtained with average grain size of 40μm. The diffusion layer with thickness of 3-8μm enriches AI and Sn atoms. Due to the high diffusion rate of Fe element along titanium alloy grain boundaries, Fe element distributes in a network structure near the interface layer.