基本信息
项目批准号：51371179
申请代码：E0103
项目名称：变形镁合金搅拌摩擦焊接头的低周疲劳行為(wèi)及失效机制研究
项目负责人：倪丁瑞
依托单位：中國(guó)科(kē)學(xué)院金属研究所
研究期限：2014-01-01 至 2017-12-31
资助经费：80.0（万元）
项目摘要
中文(wén)摘要：
搅拌摩擦焊（FSW）可(kě)实现变形镁合金的高质量连接，焊缝區(qū)织构演变是影响接头力學(xué)性能(néng)的主要因素。低周疲劳实验表明，中高应变幅下挤压态镁合金FSW接头的疲劳性能(néng)明显低于母材；FSW接头不再具有(yǒu)母材的"拉-压不对称循环变形行為(wèi)"，接头在疲劳过程中出现"材料挤出"现象，其成因还不清楚。本项目拟分(fēn)别测试挤压态与轧制态AZ31镁合金FSW接头的低周疲劳性能(néng)，研究FSW接头的低周疲劳失效特征行為(wèi)。采用(yòng)TEM、EBSD等技术对比分(fēn)析疲劳实验前后FSW接头微观组织的变化情况，分(fēn)析织构与孪晶对FSW接头循环变形行為(wèi)的影响。观察疲劳断口形貌，分(fēn)析裂纹形成与扩展模式。通过上述研究，阐明变形镁合金FSW接头的低周疲劳特征行為(wèi)的成因，揭示影响FSW接头疲劳失效的主导因素与影响机制，提出强化其疲劳性能(néng)的技术路線(xiàn)，為(wèi)镁合金FSW工艺优化提供思路，為(wèi)镁合金焊接结构件的安全设计和可(kě)靠使用(yòng)提供理(lǐ)论依据与数据积累。
英文(wén)摘要：
Wrought Mg alloys joints with high quality can be produced by friction stir welding (FSW). Texture evolution in the weld is the main factors that influence the mechanical properties of the joints. Our experiments showed that although the FSW joints of an as-extruded Mg alloy may exhibit good fatigue resistances at low strain amplitudes, the joints showed apparently lower fatigue resistances at higher strain amplitudes. Meanwhile, the FSW joints did not exhibit the phenomenon of "asymmetric cycle tension-compression deformation behavior" which is relative to the base metal; meanwhile, the phenomenon of "material-extrusion" appeared in the welds of the FSW joints. However the reason for the appearance of the unusual phenomena and their effect are not clear. In this project, AZ31 alloys under as-rolled and as-extruded conditions are to be welded by FSW, respectively, and the low cycle fatigue properties of the FSW joints are to be tested using a fatigue-testing machine. Based on the two unusual phenomena, the low cycle fatigue behavior and its effect mechanism of the FSW joints for wrought magnesium alloys are to be investigated. Microstructures of the joints before and after the fatigue testing are to be analyzed mainly using TEM and EBSD. The effect of texture and twinning on the cyclic deformation behavior of the joints is to be analyzed. The morphologies of fracture surface are to be observed under SEM, and the initiation and propagation modes of fatigue cracks in the joints are to be established. Based on the above analysis, the reason for the appearance of the unusual phenomena and their effect are expected to be elucidated. The key factors and mechanisms that influence the fatigue properties of the FSW joints are expected to be explained. The strengthening methods for the fatigue properties of the FSW joints are to be established. This project would provide an idea for optimizing the FSW process of magnesium alloys; meanwhile, it would provide essential theory and experimental data support for the safe design and reliable service of welded structural members made from magnesium alloys.
 
——来自https://kd.nsfc.gov.cn/