AZ31镁合金疲劳变形过程中{10-12}-{10-12}二次孪晶诱发疲劳断裂的裂纹扩展机制的研究  

Crack Propagation Mechanism of{10-12}-{10-12}Secondary Twin Induced Fatigue Fracture during Fatigue Deformation of AZ31 Magnesium Alloy

作　　者：闫玉芹 李梦智 游云翔 王意志 黄星宇 谭力 周涛[1] YAN Yuqin;LI Mengzhi;YOU Yunxiang;WANG Yizhi;HUANG Xingyu;TAN Li;ZHOU Tao(College of Materials Science and Engineering,Chongqing University of Technology,Chongqing 400054,China;Chongqing Yujiang Die-casting Co.,Ltd.,Chongqing 400000,China)

机构地区：[1]重庆理工大学材料科学与工程学院,重庆400054 [2]重庆渝江压铸股份有限公司,重庆400000

出　　处：《精密成形工程》2024年第11期57-64,共8页Journal of Netshape Forming Engineering

基　　金：重庆市自然科学基金(cstc2020jcyj-msxmX0877);重庆市教育委员会科学技术研究项目(KJQN202201160);重庆理工大学科研创新团队培育计划项目(2023TDZ010);重庆人力资源和社会保障局博士后研究项目(2022CQBSHTB3110)。

摘　　要：目的为了对镁合金裂纹萌生及材料的宏观失效进行更深入的分析,对二次孪晶诱发疲劳断裂的裂纹扩展机制进行研究。方法以AZ31镁合金为实验对象,采用室温条件下沿板材轴向方向(Normaldirection,ND),1%应变幅值的全反向拉-压循环加载,通过电子背散射衍射(ElectronBackscatterDiffraction,EBSD)和扫描电镜(ScanningElectronMicroscope,SEM)等技术手段,对疲劳断口显微组织及形貌特征进行分析。结果发现在沿ND方向1%循环加载条件下材料内部发生{10-12}-{10-12}二次孪晶,并且通过疲劳断口的金相显微图发现,裂纹附近存在大量孪晶片层,并且对这些孪晶片层通过扫描电镜放大研究,从观察的结果来看,断口裂纹处附近有微小裂纹产生,也就是{10-12}-{10-12}孪晶所形成的二次微裂纹,表现为在{10-12}一次孪晶界面内部的{10-12}-{10-12}二次孪晶界面所形成的台阶状裂纹。结论{10-12}-{10-12}二次孪晶在{10-12}一次孪晶交互处产生,微裂纹起始于{10-12}一次孪晶边界与{10-12}-{10-12}二次孪晶边界的交界处,分别沿一次{10-12}孪晶界和{10-12}-{10-12}二次孪晶界进行扩展,随着循环次数的增加,{10-12}-{10-12}二次孪晶界面的微裂纹会与一次孪晶界面的裂纹相互融合,并扩展到相邻晶粒内部,形成引发疲劳失效的长程裂纹,最终导致材料内部裂纹不断扩大,进而使材料发生断裂。The work aims to study the crack propagation mechanism of fatigue fracture induced by secondary twins to fur-ther analyze the crack initiation and macroscopic failure of magnesium alloy.The microstructure and morphology of fatigue fracture of AZ31 magnesium alloy were analyzed by electron backscattering diffraction(EBSD)and scanning electron micros-copy(SEM)under full reverse tension-compression cyclic loading with 1%strain amplitude along the plate axial direction(ND)at room temperature.It was found that{10-12}-{10-12}secondary twins occurred inside the material under 1%cyclic loading along the ND direction,and it was found that a large number of twin layers existed near the crack through the metallographic microscopy of the fatigue fracture,and these twin layers were amplified by scanning electron microscopy.According to the ob-servation results,there were tiny cracks near the crack.Those were,the secondary microcracks formed by{10-12}-{10-12}twins appeared as steps caused by many{10-12}-{10-12}secondary twin interfaces formed in{10-12}primary twins.It is con-cluded that{10-12}-{10-12}secondary twins occur at the interaction interfaces with{10-12}primary twins,and microcracks start at the junction of the{10-12}primary twin boundary and the{10-12}-{10-12}secondary twin boundary.It expands along the primary{10-12}twin boundary and the secondary{10-12}-{10-12}twin boundary,respectively.With the increase of the number of cycles,the micro-cracks of the secondary{10-12}-{10-12}twin interface will merge with the cracks of the primary twin interface and expand into the adjacent grains,forming long cracks that cause fatigue failure.Eventually,the cracks inside the material will continue to expand and the material will fracture.

关 键 词：AZ31镁合金 {10-12}-{10-12}二次孪晶 裂纹萌生 疲劳 断裂 

分 类 号：TG146.2[一般工业技术—材料科学与工程]