β型Ti40阻燃钛合金高温长期作用的第二相及其对性能的影响

The Second Phases and Their Effects on Properties in Ti40 Burn Resistant Titanium Alloy Thermally Exposed for Long Time

研究了β型 Ti4 0阻燃钛合金高温长期作用的第二相及其对性能影响。 Ti4 0合金高温长期作用后 ,从β相中析出 Ti5Si3相和α相 ;采用常规锻造工艺不高于 5 4 0℃热暴露 10 0 h,Ti5Si3相沿晶界不连续分布 ,降低合金热稳定性能 ;70 0℃热暴露 10 0 h,Ti5Si3相明显 ,大大降低合金热稳定性能 ,合金呈脆性沿晶界断裂 ;采用等温锻造工艺5 4 0℃热暴露 10 0 h,晶内析出粗大的 Ti5Si3相和α相 ,热稳定性能严重降低 ,呈宏观脆性断裂。采用常规锻造工艺合适的热处理制度 ,5 4 0℃ ,10 0 h,2 5 0 MPa蠕变作用后 Ti5Si3相沿晶界不连续分布 ,合金有较好的蠕变性能 ;若热处理工艺不当 ,合金中有大量粗大的棒状 Ti5Si3相和α相析出 ,Ti5Si3相沿晶界连续分布 ,合金的蠕变抗力明显降低 ;采用等温锻造工艺蠕变作用后 ,合金中析出大量粗大的α相 ,合金蠕变抗力也明显降低。

The second phases in Ti40 alloy after thermal exposure for a long time were found to be Ti5Si3 and a phases and their effects on the creeping properties of alloy were studied. It is found that the Ti5Si3 precipitates along grain boundary are not continuous, which lead to the decrease of thermal stability after exposure below 540degreesC for conventional forging. The Ti5Si3 precipitates grow greatly after exposure at 700degreesC for 100 h, which results in great decrease of the thermal stability and its tensile fractograph seems to be brittle intergranular fracture. The coarse Ti5Si3 and a phases appear after exposure at 540degreesC for 100 h for isothermal forging, reducing the thermal stability greatly. The Ti5Si3 precipitates along grain boundary are not continuous after creep exposure at 540degreesC, 250 MPa for 100 h so that the alloy has good creeping property for conventional forging; however, there are many coarse rod-like Ti5Si3 and a phase if the heat treatment is unsuitable which reduce the creeping property greatly. Many coarse a phases emerge after creeping for isothermal forging, which lead to the great reduction of creeping resistance.