摘要
SP700钛合金(Ti-4.5Al-3V-2Fe-2Mo)具有非常优异的低温超塑性和较宽的低温热加工窗口。本文分别采用最大m值法和恒应变速率法,针对SP700钛合金搅拌摩擦焊接头超塑性变形行为进行了研究。研究结果表明:采用最大m值法在795℃获得了最大超塑延伸率为989.9%;采用恒应变速率法,在795℃、应变速率为5×10-4s-1条件下获得最大超塑延伸率为687%。两种方法较母材的最佳超塑温度(765℃)均有所提高。对比搅拌摩擦焊焊核区的细晶组织,经超塑拉伸变形后,微观组织晶粒粗化严重,且β相含量减少。引起晶粒显著粗化的原因可能是经搅拌摩擦焊剧烈的塑性变形后导致的晶粒内部畸变能增加,在后续的超塑变形过程中晶粒长大势能增加所致。较高应变速率条件下的变形机制为晶粒拉长、长大、断裂和再结晶球化。搅拌摩擦焊焊接接头焊核区及热机械影响区存在较为明显的组织不均匀,经超塑变形可有效改善搅拌摩擦焊焊接接头的组织不均匀性。
SP700 titanium alloy(Ti-4.5 Al-3 V-2 Fe-2 Mo)has excellent superplasticity and relatively wider hot working map at low temperature.This paper used two method to study superplastic deformation behavior of the joint of FSW(friction stir welding)SP700 titanium,as maximum m value method and constant strain rate method.The results showed that a elongation of 989.9%was obtained at795 with maximum m value method;and a elongation of 687%was obtained at 795℃and 5×10-4 s-1 with constant strain rate method.The optimum superplastic deformation temperatures were all higher than that of base materials by two methods.Compared with the finer microstmcture at nugget zone of FSW,the grains grew seriously after superplastic deformation,and the volume of beta phase comparably decreased.The reason for the coarse grains after SPF was because the finer grains had higher distortion energy,and during SPF process the potential energy for the grain growing comparably highly increased.The deformation mechanism at higher strain rate was that grains were elongated,grown,fractured and equixed recrystallization.Microstructure in NZ(nugget zone)and TMAZ(thermo-mechanically affected zone)of FSW joint was obviously non-uniform,however,it could be effectively improved after superplastic deformation.
作者
付明杰
李继忠
曾元松
Fu Mingjie;Li Jizhong;Zeng Yuansong(AVIC Manufacturing Technology Institute,Beijing 100024,China;Aeronautical Key Laboratory for Plastic Forming Technology,Beijing 100024,China;Beijing Key Laboratory of Digital Plasticity Forming Technology and Equipment,Beijing 100024,China;China FSW Center,Beijing 100024,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2020年第1期1-8,共8页
Chinese Journal of Rare Metals
基金
国家科技部万人计划项目(2069999)资助.
作者简介
付明杰(1981-),男,内蒙古赤峰人,博士,高级工程师,研究方向:钛合金超塑成形技术,电话:010-85701254,E-mail:fumjl981@126.com
