厚板铝合金搅拌摩擦焊接头沿板厚方向低周疲劳性能不均匀性研究  

STUDY ON NONHOMOGENEITY OF LOW-CYCLE FATIGUE PROPERTIES ALONG THICKNESS DIRECTION OF PLATE FOR FRICTION STIR WELDED ALUMINUM ALLOY JOINT

作　　者：徐韦锋[1,2] 刘金合[1,2] CHEN Daolun 

机构地区：[1]西北工业大学凝固技术国家重点实验室,西安710072 [2]西北工业大学材料学院陕西省摩擦焊接工程技术重点实验室,西安710072 [3]Department of Mechanical and Industrial Engineering, Ryerson University

出　　处：《金属学报》2015年第5期587-596,共10页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目51405392;教育部博士点新教师基金项目20136102120022;陕西省自然科学基金项目2013JQ6001;中央高校基本科研业务费专项资金项目3102015ZY023资助~~

摘　　要：对2219-T62铝合金母材和搅拌摩擦焊(FSW)接头沿板厚方向分层切片分别进行了低周疲劳实验研究,探讨了热力耦合作用不均匀性和焊接工艺参数对接头低周疲劳变形行为的影响.结果表明:在低外加总应变幅0.1%和0.2%时,低周疲劳循环应力幅和塑性应变幅曲线呈水平分布,疲劳裂纹萌生于试样表面且具有单一性,裂纹扩展区有明显的疲劳辉纹;在高应变幅0.4%,0.6%和0.8%时,应力幅升高,塑性应变幅降低,发生循环硬化,且随着应变幅的增加,疲劳循环应变硬化程度逐渐升高,裂纹萌生具有多源性,以韧窝断裂特征为主.母材疲劳寿命高于FSW接头;与接头中部和底部切片相比,上部疲劳寿命较低.随转速的升高,疲劳寿命降低,焊速对其影响较小.The low- cycle fatigue tests have been conducted for the base material and friction stir welded（FSW） joints along the thickness direction of 20 mm 2219-T62 aluminum alloy thick plate. The influence of coupled thermal-mechanical and welding parameters on the fatigue deformation behavior of the joint has also been systematically investigated. The results show that stress amplitudes and plastic strain amplitudes present horizontal distribution during cyclic deformation at low strain amplitudes of 0.1% and 0.2%. Moreover, single fatigue crack initiates from the surface or near-surface defects and propagation zone is basically characterized by fatigue striations.While at higher strain amplitudes of 0.4%, 0.6% and 0.8%, the stress amplitude increases and the plastic strain amplitude decreases as cyclic deformation proceeded, indicating that cyclic hardening occurred, and the degree of hardening increases. The fracture surface presents a multi-source initiation and dimple-like features. Based metal（BM） exhibits higher stress amplitude and low hysteresis energy at mid- life which causes less fatigue damage at the same strain amplitude, resulted in a longer fatigue lifetime. Compared to middle and bottom slices, the top has higher stress amplitude and lower plastic strain amplitude corresponding to a lower fatigue life. Moreover, both the propagation zone area in the top and bottom slice are basically the same, fatigue striation in the bottom increases.The higher the rotational rate, the higher the stress amplitude, the lower the plastic strain amplitude and fatigue life,but no strong effect of the welding speed on the fatigue life can be seen.

关 键 词：搅拌摩擦焊接 厚板铝合金 低周疲劳性能 循环变形 断裂机理 

分 类 号：TG146.4[一般工业技术—材料科学与工程]