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首页> 外文期刊>Journal of Materials Engineering and Performance >Microstructure Evolution and Mechanical Properties of Keyhole Repair Welds in AA 2219-T851 Using Refill Friction Stir Spot Welding
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Microstructure Evolution and Mechanical Properties of Keyhole Repair Welds in AA 2219-T851 Using Refill Friction Stir Spot Welding

机译：AA 2219-T851中锁孔修复焊缝的微观结构演化与机械性能

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摘要

The search for a suitable friction-based keyhole repair technique that fulfills the requirements for high-quality repair welds has become an important research topic, especially for aerospace applications. In order to provide and analyze an universal keyhole repair method for lightweight metals, refill friction stir spot welding is applied to through-hole repairs in 3- and 6-mm-thick sheets of precipitate hardening AA?2219-T851. Keyholes with a diameter of 7.5?mm were repair welded achieving a defect-free microstructure. The correlation between the microstructural evolution imposed by the repair process and the resulting mechanical properties is shown. A comprehensive analysis of the precipitate evolution in peak-aged AA?2219 during RFSSW is presented. Thermal cycle measurements revealed high heating rates and peak temperatures of up to 520?°C in the weld center. The thermal cycle caused mainly dissolution and minor equilibrium phase formation in the stirred zone. In the HAZ, overaging of the strengthening precipitates dominates with minor dissolution and equilibrium phase formation only in the direct proximity of the SZ. Microstructural analysis revealed typical weld zone formation with inhomogeneous grain size distribution in the SZ. The resulting mechanical properties are dominated by an inhomogeneous hardness distribution with lowest hardness in the TMAZ at 5?mm from the center of the weld. During tensile loading main yielding and the final fracture occur in the area of lowest strength. Tensile testing showed yield strength of 40 to 46% and UTS of 28 to 25% below BM values in 3- and 6-mm-thick sheets, respectively. The sheet thickness and post-weld natural aging were found to influence the mechanical properties of the weld significantly.
机译：寻找合适的基于摩擦的钥匙孔修复技术，满足高质量修复焊缝的要求已成为一个重要的研究主题，特别是对于航空航天应用。为了提供和分析轻质金属的通用钥匙孔修复方法，将摩擦搅拌点焊接施加到3-和6mm厚的沉淀物硬化AAαα219-T851中的通孔维修。直径为7.5Ωmm的钥匙孔是修复焊接，实现无缺陷的微观结构。示出了修复过程施加的微观结构演化与所得的机械性能之间的相关性。介绍了RFSSW期间峰值AAα的沉淀液进化综合分析。热循环测量显示焊接中心中的高加热速率和高达520Ω°C的高热速率和峰值温度。热循环主要引起搅拌区中的溶解和轻微平衡相形成。在HAZ中，强化沉淀物的过度统计占SZ的直接邻近的轻微溶解和平衡相形成。微观结构分析揭示了SZ中具有不均匀晶粒尺寸分布的典型焊接区。由此得到的机械性能通过在焊缝中心5Ωmm的TMAZ中具有最低硬度的不均匀硬度分布。在拉伸载荷期间，在最低强度的面积中发生最终骨折。拉伸试验分别显示出屈服强度为40至46％，28％至25％以下，低于3毫米厚的薄片。发现薄板厚度和焊接后天然老化显着影响焊缝的机械性能。

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