CAJ | 학술논문

对不同温度下退火处理后的细晶TC4合金板材进行超塑性拉伸变形，研究该合金在750~850℃，应变速率为3×10-4~1×10-3 s-1条件下的超塑性拉伸变形行为，分析晶粒尺寸、变形温度和β相含量对合金性能的影响。结果表明：退火后的(α+β)型细晶Ti-6Al-4V合金表现出良好的超塑性，并且晶粒越细，最佳超塑性变形温度越低。晶粒直径为2.5μm、β相含量(体积分数)为9.6%的TC4合金在温度为800℃、应变速率为1×10-3 s-1的变形条件下，伸长率最大，达到862%。不同晶粒度合金的应变速率敏感系数m均随变形温度升高先上升后下降，最高达0.61。β晶粒处于α晶粒三叉晶界处，升温或拉伸变形时聚集并沿α晶界长大，形成细长的β晶粒并逐渐变粗大，因此在900℃以上高温下合金的超塑性变形能力降低。
대불동온도하퇴화처리후적세정TC4합금판재진행초소성랍신변형，연구해합금재750~850℃，응변속솔위3×10-4~1×10-3 s-1조건하적초소성랍신변형행위，분석정립척촌、변형온도화β상함량대합금성능적영향。결과표명：퇴화후적(α+β)형세정Ti-6Al-4V합금표현출량호적초소성，병차정립월세，최가초소성변형온도월저。정립직경위2.5μm、β상함량(체적분수)위9.6%적TC4합금재온도위800℃、응변속솔위1×10-3 s-1적변형조건하，신장솔최대，체도862%。불동정립도합금적응변속솔민감계수m균수변형온도승고선상승후하강，최고체0.61。β정립처우α정립삼차정계처，승온혹랍신변형시취집병연α정계장대，형성세장적β정립병축점변조대，인차재900℃이상고온하합금적초소성변형능력강저。
Superplastic tensile deformation behavior was studied on fine-grained Ti-6Al-4V alloy sheets which are achieved from annealing treatment at temperature of 750~850℃and strain rate range of 3×10-4~1×10-3 s-1. And the effect of the grain size, deformation temperature andβphase volume fraction on the properties of the alloy were analyzed on superplastic deformation capacity. Result shows that fine-grained Ti-6Al-4V alloys has excellent superplasticity. When the Ti-6Al-4V alloy with the average grain size of 2.5 μm and beta volume fraction of 9.6% was deformed at the temperature of 800 ℃ and strain rate of 1×10-3 s-1, the highest elongation of 862% can be obtained. The sensitivity value (m) of the Ti-6Al-4V alloy with different grain size increase first and then decrease as the deformation temperature increases. The largest number of m value reaches 0.61. The beta grains locate at the triple junctions of alpha grains and they will agglomerate and grow along the triple junctions to form slender beta grains and grow coarsen. The optimum superplastic deformation temperature is largely decreased compared to traditional Ti-6Al-4V alloy for commercial use.