热暴露和热盐暴露的交互作用对Ti811合金热盐应力腐蚀性能的影响

EFFECTS OF INTERACTION BETWEEN HOT EXPOSURE AND HOT SALT EXPOSURE ON HOT SALT STRESS CORROSION BEHAVIOR OF Ti811 ALLOY

Ｔｉ８Ａｌ１Ｍｏ１Ｖ（Ｔｉ８１１）合金对热盐应力腐蚀（ＨＳＳＣ）较敏感，单个因素对合金ＨＳＳＣ行为影响已有研究，而复合因素的影响研究很少。采用工业生产的Ｔｉ８１１合金棒材，经双重退火后，研究了热暴露和热盐暴露的交互作用对合金ＨＳＳＣ性能的影响。结果表明：４２５℃实验条件下，热暴露和热盐暴露交互作用与单热盐应力腐蚀相比使合金的ＨＳＳＣ性能明显降低。延伸率由１８％降至６％；合金中存在位错在晶界处塞积诱发的沿晶裂纹，腐蚀产物易于在裂纹尖端积聚。导致沿晶断裂，加速腐蚀。此外，在交互作用过程中，合金中α２（Ｔｉ３Ａｌ）脆性相的析出以及晶间β相发生转变，使合金的ＨＳＳＣ敏感性增大，并加速热盐应力腐蚀。

Ti811(Ti8Al1Mo1V) alloy is sensitive to hot salt stress corrosion (HSSC), effects of single factor on the alloy's HSSC behavior were studied, but the effects of compound factors on its HSSC behavior have been seldom reported. Effects of interaction between hot exposure and hot salt exposure on its HSSC behavior were studied, the results indicate that interaction between hot exposure and hot salt exposure leads to an obvious decrease of HSSC properties compared with that of hot salt exposure, for example, its elongation reduces from 18% to 6%; dislocations pileup appear on grain boundary, which induces microcracks along grain boundary and leads to intergranular cracking. In addition, α2(Ti3Al) phase precipitates and intergranular β transforms during the interaction process, its HSSC sensitivity increases and HSSC is accelerated.