Two typical microstructures of Ti–6.6Al–1.7Mo–2.3V–1.9Zr (TA15) titanium alloy were successfully fabricated by vacuum hot pressing using TA15 metallic powders of two different sizes with the spherical shape of particles. The size of prior β grains was consistent with the size of the as-received TA15 alloy powder. The microstructure of TA15 alloys differed depending on the size of the initial powder, forming Widmanstätten patterns for the sample from coarse powder or equiaxed microstructure for fine powder. The microstructure evolution during the vacuum hot pressing included solid-state phase transition and powder compact. In the temperature-rise period, the solid-state phase transition occurred (α → β). The anterior β-grain only grew to the original powder interface, which means that it would not coarsen causing its size to exceed that of the original powder. The solid-state phase transition occurred (β → α) when the temperature decreased during the subsequent cooling process. The nuclei of grain boundaries α appeared at the grain boundary of the anterior β-grain. Then the nuclei of grain boundaries α grew together enclosing the anterior β-grain. The grain boundaries α belonged to a certain anterior β-grain and could provide nucleation sites for the α-colonies of the two adjacent anterior β-grains. Finally, the α colonies grew into the anterior β-grain forming the Widmanstätten structure. The two typical microstructures will likely affect the mechanical properties of the TA15 alloys. An improvement in tensile properties was evident in the TA15 alloys (equiaxed microstructure) fabricated from a fine powder compared to their predecessors, consisting of colonies α microstructure fabricated from the coarse powder. To be specific, the tensile strength increased from 849 to 898 MPa and the ductility growth was from 5.5 to 6.5%.

采用两种不同尺寸、颗粒形状为球形的TA15金属粉末，通过真空热压成功制备了Ti-6.6Al-1.7Mo-2.3V-1.9Zr（TA15）钛合金的两种典型微观结构。原始β晶粒的尺寸与原始TA15合金粉末的尺寸一致。TA15合金的显微组织根据初始粉末的尺寸而不同，粗粉末形成魏德曼组织，细粉末形成等轴组织。真空热压过程中的微观结构演变包括固态相变和粉末压坯。在升温阶段，发生固态相变（α→β）。前面的β晶粒仅生长到原始粉末界面，这意味着它不会粗化而导致其尺寸超过原始粉末的尺寸。当随后的冷却过程中温度降低时，发生固态相变（β→α）。晶界α核出现在前β晶粒的晶界处。然后晶界α的核一起生长，包围前面的β晶粒。晶界α属于某个前β晶粒，可以为相邻的两个前β晶粒的α集落提供成核位点。最后，α集落生长成前部β晶粒，形成魏德曼斯塔滕结构。这两种典型的微观结构可能会影响TA15合金的机械性能。与由粗粉末制造的α团簇组成的前身相比，由细粉末制造的TA15合金（等轴微观结构）的拉伸性能明显改善。具体来说，抗拉强度从849 MPa增加到898 MPa，延展性从5.5%增加到6.5%。