采用扫描电镜(SEM)原位拉伸法观察TC4钛合金激光焊接接头各微区孔洞形核与成长、损伤与断裂行为,研究接头微观组织对其损伤和断裂行为的影响.结果表明:焊缝区裂纹形核于晶内孪晶、滑移线与晶界交汇处,主裂纹形成直至最终断裂；热影响区多裂纹起裂,单一裂纹扩展至最终断裂；母材区孔洞优先形核于相界面及晶界区域,缺口前端孔洞群相互贯穿直至最终断裂.当应变超过0.023时,母材区及热影响区靠近母材一侧从协调变形向以界面微孔洞的行核与聚合为主转化；焊缝区粗大晶粒内部网篮状马氏体存在且晶界面积较小,导致变形机制未发生改变,促使其力学性能低于焊缝的.%In order to investigate the effects of microstructures on damage evolution and fracture behavior in laser welded joint for Ti-6A1-4V alloy, the microvoids nucleation, growth, coalescence and crack were observed by in-situ tensile test. The results show that the crack in the weld metal grows rapidly when it nucleates at the twin boundary of the inner grain , and the intersection of slip line and grain boundary. The multi-cracks in the heat-affected zone (HAZ) occur in front of the notch, one crack propagation leads to the final fracture. When the strain exceeds 0.023, the deformation mechanism in the base metal and HAZ near the base metal changes from compatible deformation to bluntness and expansion alternately when the microvoid is nucleated firstly along the grain boundary. The deformation mechanism in the welded metal does not change due to its coarse martensite and small grain boundary. Therefore, the tensile stress in the welded metal is higher than that in the other areas.
展开▼
