直接激光沉积Ti6Al4V合金疲劳裂纹萌生原位研究  

In⁃situ study on fatigue crack initiation of direct laser deposition Ti6Al4V alloy

作　　者：谢强[1] 吕俊霞[1] 周建力 程晓鹏 王晋 张跃飞 张泽[2] XIE Qiang;LÜJun-xia;ZHOU Jian-li;CHENG Xiao-peng;WANG Jin;ZHANG Yue-fei;ZHANG Ze(Faculty of Materials and Manufacturing,Beijing University of Technology,Beijing 100124;School of Materials Science and Engineering,Zhejiang University,Hangzhou Zhejiang 310027,China)

机构地区：[1]北京工业大学材料与制造学部,北京100124 [2]浙江大学材料科学与工程学院,浙江杭州310027

出　　处：《电子显微学报》2022年第5期542-549,共8页Journal of Chinese Electron Microscopy Society

基　　金：国家自然科学基金基础科学中心项目(No.51988101);北京市自然科学基金重点项目(No.KZ20211000506).

摘　　要：本文运用自主研发的扫描电镜(SEM)原位疲劳测试台,对直接激光沉积(DLD)制备的Ti6Al4V合金开展疲劳实验,研究了其裂纹萌生行为。实验结果表明,在疲劳测试过程中,Ti6Al4V合金微塑性应变累积会导致颈缩,其中滑移是主要的塑性变形方式。通过对变形行为的研究发现,网篮组织和α集束具有不同的织构特征,进而具有不同的变形方式。α集束内晶粒取向一致,滑移带会在集束边界形成,但集束内表现为均匀变形;网篮组织内具有高占比(96%)的高角度晶界,容易导致位错在晶界处塞积并形成滑移带,随着塑性应变累积,微孔及微裂纹沿滑移带边界萌生。同时研究发现小尺寸的表面缺陷(尺寸约为2~3μm)对Ti6Al4V合金疲劳性能影响较小,基本不会引起疲劳裂纹扩展。In this paper,the fatigue test of Ti6Al4V alloy prepared by direct laser deposition(DLD)was carried out by using the self⁃developed scanning electron microscopy(SEM)in⁃situ fatigue test stage,and the crack initiation behavior was studied.The experimental result show that the micro plastic strain accumulation of Ti6Al4V alloy leads to necking during fatigue test,and slip is the main plastic deformation mode.Through the study of deformation behavior,it is found that basket weave andαcolony have different texture characteristics,and thus have different deformation modes.The grain orientation in theαcolony is consistent,and the slip band will form at the colony boundary,but the deformation in the colony is uniform.There is a high angle grain boundary(96%)in basket weave microstructure,which is easy to cause dislocation to accumulate at grain boundary and form slip band.With the accumulation of plastic strain,micro pores and micro cracks initiate along the boundary of slip band.At the same time,it is found that the small size of surface defects(about 2-3μm)has little effect on the fatigue properties of Ti6Al4V alloy,and basically will not cause fatigue crack propagation.

关 键 词：直接激光沉积 TI6AL4V合金 扫描电镜 原位疲劳 裂纹萌生 

分 类 号：TB31[一般工业技术—材料科学与工程] TG146.23[金属学及工艺—金属材料] V25[金属学及工艺—金属学] TG115.215.3[航空宇航科学与技术—航空宇航制造工程] TG113.255