Guo Junqing, Sun Wanting, Xiang Nan, Chen Fuxiao
School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023, China.
Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong 100872, China.
Materials (Basel). 2023 Jul 13;16(14):4981. doi: 10.3390/ma16144981.
In order to understand the strengthening and the failure mechanism of accumulative roll bonding (ARB)-processed AZ63 Mg alloy, the interfacial bonding and fracture behavior of an ARB-processed AZ63 sheet were studied through electron microscopic analysis. The correlation between the mechanical properties, the microstructure, and the ARB processing parameters of an AZ63 sheet were presented. The experimental results have demonstrated that the average grain size of AZ63 Mg alloy processed by ARB was remarkably refined from 12.8 μm to 5.7 μm when the ARB processing temperature was set to 623 K, indicating the occurrence and development of dynamic recrystallization (DRX) nucleation. With the increase in ARB passes, the microstructure obviously became uniform. However, after five passes of the ARB process at 623 K, grains with different crystallographic orientations at the interface can be rearranged to generate the coherent eutectic plane, which inhibits the further refinement of grain size. During the ARB process of the AZ63 Mg alloy, the grain refinement was controlled by twin-induced recrystallization and dynamic recrystallization. Microcracks at the bonded interface of the ARB sample were eliminated during the following 3~5 rolling passes at 623 K. After three passes of the ARB process at 623 K, the strength and elongation of the AZ63 Mg alloy increased from 232 MPa and 18.5% to 282 MPa and 26.3%, respectively. The tensile fracture morphology of the sample processed by three passes of ARB exhibited numerous dimples, and the slip lines caused by the cooperative deformation of refined grains can produce a network-like dimple structure, indicating that excellent ductile fracture characteristics could be obtained.
为了理解累积叠轧（ARB）工艺制备的AZ63镁合金的强化及失效机制，通过电子显微镜分析研究了ARB工艺制备的AZ63板材的界面结合与断裂行为。给出了AZ63板材的力学性能、微观结构与ARB工艺参数之间的相关性。实验结果表明，当ARB工艺温度设定为623 K时，经ARB工艺处理的AZ63镁合金的平均晶粒尺寸从12.8μm显著细化至5.7μm，这表明动态再结晶（DRX）形核的发生与发展。随着ARB道次的增加，微观结构明显变得均匀。然而，在623 K下进行5道次ARB工艺后，界面处不同晶体取向的晶粒可重新排列以生成共格的共晶面，这抑制了晶粒尺寸的进一步细化。在AZ63镁合金的ARB工艺过程中，晶粒细化由孪生诱导再结晶和动态再结晶控制。在623 K下后续3至5道次轧制过程中，ARB样品结合界面处的微裂纹被消除。在623 K下进行3道次ARB工艺后，AZ63镁合金的强度和伸长率分别从232 MPa和18.5%提高到282 MPa和26.3%。经3道次ARB工艺处理的样品的拉伸断口形貌呈现出大量韧窝，由细化晶粒协同变形产生的滑移线可形成网络状韧窝结构，表明可获得优异的韧性断裂特性。
