中文摘要：

研究了不同试验温度下铸态Ti40合金的高温拉伸力学性能变化规律，并采用光学显微镜和扫描电子显微镜对拉伸样断口形貌进行观测，确定其断裂机制。结果表明：合金的抗拉强度随着试验温度的升高而显著下降，而塑性则分别表现出两个塑性较优区和脆性区，即400℃以下低温和900-1000℃高温的较好塑性区以及500-800℃的热脆区和1000℃以上的高温脆性区。脆性区试样断口形貌均呈现为沿晶脆性断裂，这一断裂机制与合金粗大晶粒以及严重的氧化相关。高温塑性区断口形貌为穿晶韧性断裂，则合金具有较高的塑性和较低的变形抗力，可作为较好的热加工温度区间。

英文摘要：

High temperature tensile mechanical properties and fracture behavior of as-cast Ti40 burn resistant titanium alloy were conducted at different experimental temperatures. Macro-morphology and micro-morphology of fracture surface were observed and investigated systematically by optical microscope （OM） and scanning electron microscope （SEM）. The results show that the ultimate tensile strength decreased drastically with increasing experimental temperature. However, the percentage reduction of area exhibited excellent plasticity at both below 400 ℃ and in the temperature range of 900--1000℃ and poor plasticity above 1000 ℃ and in the temperature range of 500--800 ℃. The fracture mechanism of the alloy with very low percentage reduction of area was intergranular brittle fracture, which was attributed to the coarse grain and severe oxidation at high temperature. Meanwhile, the fracture mechanism of the alloy with very high percentage reduction of area was transgranular ductile fracture. Thus the alloy exhibited an excellent plasticity and a low deformation resistanee in the temperature range of 900--1000℃. This temperature range could be chosen as an optimal processing condition.