为了考察粉末不同批次间的粒度差异对成形钛合金产品的性能和尺寸影响，本工作选取了3种粒度(平均粒度D₅₀ = 125、94和73 μm)的Ti-5Al-2.5Sn ELI预合金粉末，采用粉末冶金热等静压工艺在940 ℃、120 MPa、3 h的制度下制备了闭式叶轮，对各叶轮进行了815 ℃、1.5 h的退火热处理，通过X射线检测等技术探测了叶轮中可能存在的孔隙缺陷，利用SEM和TEM对显微组织进行观察，并结合低温拉伸实验分析了粉末粒度对闭式叶轮本体力学性能的影响。结果表明，采用不同粒度粉末制备出的叶轮各部位显微组织均匀，本体取样力学性能均达到变形态合金水平，77 K下试棒的抗拉强度约1300 MPa，延伸率可达20%，在拉伸断口附近的组织中观察到{\mathrm{10}\overline{\mathrm{1}}\mathrm{2}}、{\mathrm{10}\overline{\mathrm{1}}\mathrm{1}}、{\mathrm{11}\overline{\mathrm{2}}\mathrm{2}}孪晶。对成形的闭式叶轮尺寸的测绘结果表明，叶轮的尺寸收缩特点与粉末粒度相关，粉末的平均粒度(D₅₀：70~130 μm)越小，体积收缩越大。采用有限元方法对粉末冶金热等静压成形后叶轮尺寸进行预测，并与制备的叶轮实测尺寸进行对比。结果表明，模拟预测的收缩规律与实际尺寸收缩一致，其中内部流道区域预测偏差值小于0.3 mm。

A shrouded impeller is an essential component of a liquid rocket, mainly responsible for transporting and pressurizing liquid fuel or oxidant. Owing to the low temperature and high-rotation speed of the working environment, materials with high performance are required for fabricating the impeller. With its excellent low temperature mechanical properties and high specific strength, Ti-5Al-2.5Sn extra-low interstitial (ELI) alloy has been widely applied in fabricating liquid rocket components, including the shrouded impeller. Considering the geometric complexity of the impeller, the powder metallurgy-hot isostatic pressing (PM-HIP) route is a suitable method for impeller formation. PM-HIP technology has a similar forming capability as precision casting but avoids casting defects, realizing the parts with reliable service performance. However, the mechanical properties and dimensional accuracy of the impeller may be influenced by the variation of powder particle sizes. Herein, three kinds of Ti-5Al-2.5Sn ELI prealloyed powders with different particle size distributions (average particle size D₅₀ = 125, 94, and 73 μm) were prepared by adjusting the process parameters of gas atomization and screen meshes. Then, their corresponding shrouded impellers were manufactured via the PM-HIP route at 940 ^oC, 120 MPa for 3 h. Subsequently, the impellers were annealed at 815 ^oC for 1.5 h, followed by air cooling. The effect of powder particle sizes on the mechanical properties of shrouded impellers was analyzed using cryogenic-temperature tensile tests. The porosity defect of impeller slices was detected using industrial computed tomography. The microstructure of the impellers was characterized using SEM and TEM. Meanwhile, the mechanism of low temperature deformation was also discussed. All three impellers exhibited homogeneous microstructure with fine grains, and their mechanical properties were comparable to the level of wrought alloys; specifically, the tensile strength was about 1300 MPa, and the elongation was 20% at 77 K. In addition, many twins were found in the deformation zones, including the types of {\mathrm{10}\overline{\mathrm{1}}\mathrm{2}}, {\mathrm{10}\overline{\mathrm{1}}\mathrm{1}}, and {\mathrm{11}\overline{\mathrm{2}}\mathrm{2}}. PM-HIP impeller size was calculated using the finite element method in the modified Gurson model and compared with the size of the actual impeller. Dimensional shrinkage was consistent between the finite element simulation result and the actual part, and the deviation in the flow channel was < 0.3 mm.