摘要
针对6 mm厚P92钢等离子弧焊接接头,利用带动态拉伸台的高分辨扫描电镜对接头的不同区域进行原位拉伸实验,通过试样动态断裂过程观察并结合断口分析研究了P92钢等离子弧焊接接头各区的微观断裂机理。结果表明:接头焊缝区在拉伸过程中经历了前期的钝化伸张区之后,裂纹起裂于中间相M_(23)C_(6)处,而焊缝区的裂纹扩展路径沿着中间相M_(23)C_(6)前进,并在断面上形成了撕裂脊,属于穿层断裂;热影响区是P92焊接接头的最薄弱环节,裂纹起裂于中间相M_(23)C_(6)处,其断口起裂的孕育阶段基本没有前期的钝化,即前期的塑性裂纹的扩展长度X_(f)=0,裂纹以沿层断裂模式进行扩展,在断口处有分层现象,最终断面呈现出裂纹以解理断裂模式进行扩展;母材区的拉伸试样在经历了钝化伸张区之后,前期的裂纹以塑性断裂模式进行扩展,裂纹在扩展过程中遇到较多的中间相M_(23)C_(6)时形成应力集中,同时在其附近出现空洞,此时裂纹以解理断裂模式进行扩展,属于沿层断裂。
The P92 steel plate of 6 mm thickness was welded by plasma welding process.High-resolution scanning electron microscope with dynamic stretching table was used to examine the micro-cracking behavior of the welded joint.Fracture processes of welding joints were observed by in-situ tensile tests,and fracture mechanism was also analyzed.The results show that the microcracks initiated at the intermediate phase M_(23)C_(6)after the earlier passivation zone,and the entire crack expansion path of the weld area was along the intermediate phase M_(23)C_(6),forming a tea-ring ridge on the section.The fracture behavior of the welded zone was a translayer fracture morphologies.The heat-affected zone was the weakest area of the P92 welding joint,and microcracks initiated at the middle phase M_(23)C_(6)without previous passivation,that is the extended length of the plastic crack in the early stage X_(f)=0.With loading increasing,the microcracks extended in the layer fracture mode and there was a layering phenomenon at the fault.The fracture behavior of the heat-affected zone was cleavage mode.After the in-situ tensile specimen in the base metal zone undergoed passivation stretch zone,the cracks propagated in a plastic fracture mode.As the expansion of the crack,there were many microvoid nucleated when the formation of stress concentration and the cracks propagating in the base metal changed from dimple fracture mode to shear fracture mode.The fracture behavior of the base metal zone was the layer fracture mode.
作者
张忠科
刘旭峰
李昭
雄健强
ZHANG Zhongke;LIU Xufeng;LI Zhao;XIONG Jianqiang(School of Materials Science and Engineering,Lanzhou University of Technology,Lanzhou 730050,China)
出处
《材料导报》
EI
CAS
CSCD
北大核心
2021年第24期24128-24133,共6页
Materials Reports
基金
甘肃省科技重大专项(18ZD2GC013)
航空科学基金(201611U2001)。
