固溶处理对Ni-Co基高温合金反常动态应变时效的影响

EFFECT OF SOLUTION TREATMENT ON THE INVERSE DYNAMIC STRAIN AGING OF A Ni-Co BASE SUPERALLOY

研究了亚固溶和过固溶处理对Ni-Co基高温合金在400和450℃和不同应变速率下拉伸时的锯齿状塑性失稳现象的影响.实验结果表明,过固溶合金的晶粒尺寸和二次γ′相间距大于亚固溶合金.2种固溶处理后的合金都表现为反常动态应变时效,其锯齿状流变现象都是由置换固溶原子和可动位错的相互作用引起的.2种固溶处理后锯齿状流变的临界应变量的差别与合金内二次γ′相的间距和塑性变形时合金内位错密度有关;其应力差值的区别与塑性变形时合金内位错密度及由晶界控制的扩散有关.

Serrated flow in a Ni-Co base superalloy was investigated after subsolvus and super- solvus solution treatments at the temperatures of 400 and 450 ℃ by tensile loading at different strain rates. The results suggested that the sizes of the grain and secondary γ^1 phase of the alloy after super- solvus solution were larger than that of the alloy after subsolvus solution. The serrated flow exhibited inverse DSA behavior after two solution treatments, which was caused by the interaction between sub- stitutional solutes and mobile dislocations. The variation of critical strain of serrated flow after two solution treatments may be related to different spacing between secondary γ^1 and different densities of mobile dislocations during plastic deformation. The different densities of mobile dislocations and the diffusion controlled by grain boundary were responsible for the variation of stress drop of serrated flow after two solution treatments.