Heterogeneous-structured Cu samples composed of coarse-grained (CG) and ultrafine-grained (UFG) domains with a transitional interface were fabricated by friction stir processing, in order to investigate the effect of interface constraint on the yielding and fracture behaviors. Tensile test revealed that the synergetic strengthening induced by elastic/plastic interaction between incompatible domains increases with increasing the area of constraint interface. The strain distribution near interface and the fracture morphology were characterized using digital image correlation technique and scanning electron microscopy, respectively. Fracture dimples preferentially formed at the interface, possibly due to extremely high triaxial stress and strain accumulation near the interface. Surprisingly, the CG domain was fractured by pure shear instead of the expected voids growth caused by tensile stress.%为了研究界面约束对异质结构材料屈服和断裂力学性能的影响,采用搅拌摩擦加工方法制备具有过渡型界面的粗晶/超细晶纯铜式样.拉伸测试结果表明:由粗晶和超细晶力学不协调单元弹?塑性交互作用所产生的协同强化效应随约束面积的增加而增加.使用数字散斑相关方法揭示异质结构材料颈缩过程中界面区域的应变集中分布.使用扫描电子显微镜系统分析断口形貌特征.结果发现,界面区域分布有大量大尺寸韧窝,这可能是因为粗晶与超细晶的交互约束作用在界面处产生高三轴内应力和塑性应变累积.此外,还发现粗晶区域通过剪切方式断裂,而不是拉伸应力所引起的韧窝生长机制.
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