2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas （TIG） arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zo...2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas （TIG） arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zone （PMZ）. Effects of the PMZ on the fracture behavior were systematically studied. Continuous intergranular eutectics were observed in the PMZ close to the fusion line. Away from the fusion line, the intergranular eutectics in the PMZ became discontinuous. The fracture morphology and the microhardness distribution of the joint showed that the PMZ was gradient material with different mechanical properties, which strongly affected the fracture process. It was observed that the crack initiated in the PMZ near the front weld toe, and propagated in the PMZ away from the fusion line. Then, the crack tip was blunt when it propagated into the PMZ with higher plasticity. Finally, the rest part of the joint was shear fractured.展开更多
文摘作为热结构材料,陶瓷基复合材料(ceramic matrix composites,CMC)在航空航天领域应用潜力巨大。连续纤维的引入解决了陶瓷脆性大的问题,而纤维与基体间微小区域——界面层的设计是保证CMC具有高韧性的关键。一直以来相关研究主要集中于界面层与CMC宏观力学性能之间的关系,受限于表征难以深入研究界面层微区力学行为的困难。随着微纳力学测试与聚焦离子束(focused ion beam,FIB)技术的发展,近些年来对于CMC界面层结合强度以及其失效行为的表征逐渐增多。在此基础上,本文综述CMC中界面层的作用以及界面剪切强度的影响因素与调控机制,同时汇总当下通过直接或间接手段测试界面剪切强度的方法,重点总结微纳力学手段下纤维push-out/push-in以及微柱压缩等方法的适用条件以及差异,报道这些方法在界面区失效机制研究方面的进展,并指明尚存在的一些问题。其中,纤维pushout/push-in可以反映基体应力作用对界面剪切强度的影响,但测试结果可能受到外部因素的影响;而微柱压缩测试则更多地反映界面层本征特性,无法反映基体应力对界面剪切强度的影响,也无法反映纤维拔出过程。最后展望未来的研究方向:进一步拓展界面微区力学行为的表征方法,同时确定微区力学与宏观力学性能间的影响机制并建立模型,最终实现CMC的界面层优化。
文摘2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas （TIG） arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zone （PMZ）. Effects of the PMZ on the fracture behavior were systematically studied. Continuous intergranular eutectics were observed in the PMZ close to the fusion line. Away from the fusion line, the intergranular eutectics in the PMZ became discontinuous. The fracture morphology and the microhardness distribution of the joint showed that the PMZ was gradient material with different mechanical properties, which strongly affected the fracture process. It was observed that the crack initiated in the PMZ near the front weld toe, and propagated in the PMZ away from the fusion line. Then, the crack tip was blunt when it propagated into the PMZ with higher plasticity. Finally, the rest part of the joint was shear fractured.
