中文摘要：

采用高能球磨-放电等离子烧结技术制备具有双尺度显微组织的Ti-6Al-4V合金，并研究烧结温度和加入未球磨粉末的比例对烧结试样显微组织及力学性能的影响。实验结果表明：当球磨时间为6h时，由于球磨粉末内部的应变量不均匀，球磨粉末烧结试样的显微组织均由粗晶网篮组织和细晶等轴组织组成。随烧结温度升高，烧结试样的密度逐渐提高，细晶区的晶粒尺寸逐渐增大，材料强度呈先上升后下降的趋势。在球磨粉末中加入一定比例的未球磨粉末可显著提高烧结材料的塑性，并且保持较高的强度。当球磨粉末与未球磨粉末按质量比4：1混合、SPS烧结温度为850℃、保温时间为4 min时，烧结材料相对密度达到99.0%，细晶区晶粒尺寸为1~2μm，烧结试样获得最佳强度-塑性组合，其拉伸屈服强度为1012 MPa，断裂强度为1056 MPa，伸长率为10%。

英文摘要：

Bimodal-structured Ti-6Al-4V alloys were prepared by high-energy ball-milling and subsequent spark plasma sintering （SPS）. The effects of sintering temperature and volume fraction of unmilled powders on the microstructure and mechanical properties of SPSed titanium alloys were investigated. Experimental results show that the sintered samples exhibit bimodal microstructures consisting of coarse-grained basketweave regions and fine-grained equiaxed regions as a result of strain inhomogeneity within the milled powders （6 h）. Increasing sintering temperature, the relative densities of sintered samples increase, the equiaxed fine grains tend to grow up gradually, and the tensile strengths increase first and then decrease. Moderate addition of unmilled powders into ball milled powders can cause an increase of the volume fraction of coarse grain regions, which leads to an enhanced ductility without much decrease in strength. When the blended powders （20%unmilled） are sintered at 850℃for 4 mins, the sintered sample with a relative density of 99.0%and the grain sizes of 1~2μm in fine-grained regions can be obtained, whose tensile yield strength, fracture strength and ductility are 1 012 MPa, 1 056 MPa and 10%, respectively.