烧结温度对TC4合金的微观结构和力学性能的影响

将TiH₂、Al-V粉末压制成型后进行真空烧结，制备出Ti6Al4V(TC4)合金，使用XRD、金相和SEM断口形貌观测以及力学性能测试等手段对其表征，研究了烧结温度对合金力学性能的影响。结果表明：烧结样品由密排六方α-Ti和体心立方β-Ti双相组成，其形貌呈等轴、网篮或板条(片状、针状)状，随着烧结温度的提高和保温时间的延长等轴组织减少，片状组织和针状组织增加且其组织粗化，在1150℃烧结的样品具有较好网篮结构组织；用该方法可制备相对密度为96.9%~99.6%、抗拉强度为719.3~914.1 MPa、延伸率为6.2%~9.4%、硬度为313.2~364.8HV的TC4合金试样；在1150℃保温1.5 h的样品性能较好，其抗拉强度最高(914.1 MPa)，对应的延伸率和硬度分别为7.6%和355.5HV；用纯TiH₂粉末烧结样品的断口呈韧性断裂；加入合金元素的样品其断口逐渐由韧性断口变为韧性和脆性混合的断口，其强度提高、延伸率下降。

Effect of Sintering Temperature on Microstructure and Mechanical Properties of TC4 Alloy

Ti6Al4V (TC4) alloy was prepared by vacuum sintering of the pressed powder mixture of TiH₂, Ti and Al-V alloy. The effect of sintering temperature on the phase constituents, microstructure , density and mechanical properties of the alloy was characterised by XRD, metallography, mechanical tests and SEM fracture morphology. The result shows that the prepared alloy composed of hexagonal α-Ti phase and body-centered cubic β-Ti phase. The alloy presents a microstructure with equiaxed grains, as well as mesh basket or lath (lamellar and acicular) like structures. With the increase of sintering temperature and holding time, the equiaxed grains gradually disappeared, while the amount of lamellar- and acicular-like structures increase and which then were coarsened . The alloy sintered at 1150℃ presents a microstructure with better mesh basket like structures. TC4 Ti-alloyswith relative density of 96.9%~99.6%, tensile strength of 719.3~914.1 MPa, elongation at break of 6.2%~-9.4% and hardness of 313.2~364.8 HV can be obtained by the method. Among others, the alloy with the best mechanical property could be acquired by sintering at 1150℃, which shows tensile strength of 914.1MPa, elongation at break of 7.6% and hardness of 355.5 HV respectively. The fracture morphology was mainly ductile for the alloy prepared by sintering of powder mixture of Ti and pure TiH₂ , and it gradually turns into brittle-tough mixed fracture with the increasing amount of Al-V alloy powder was added, correspondingly, the tensile strength of the prepared alloys increased but the elongation at break decreased.