材料期刊网

目的：研究超声冲击处理对7 A52铝合金焊接接头表层组织及性能的影响。方法用双丝MIG焊接方法对7 A52铝合金进行焊接,采用UIT-125型超声冲击机对其焊接接头进行全覆盖处理；通过金相显微镜,对超声冲击处理后的焊接接头组织变化规律进行观察分析；利用显微硬度计和磨擦磨损试验机测试研究其接头力学性能。结果超声冲击处理后,焊趾处形成相对连续、均匀、光滑的过渡圆弧,可以有效地缓解焊接接头的应力集中,7 A52铝合金焊接接头表面得到了明显强化,形成一层致密的塑性变形层,接头表面晶粒细化,母材的表层塑性变形厚度可达15μm左右,热影响区的表层塑性变形厚度可达25μm左右,显微硬度和耐磨性显著提高。结论经超声冲击处理后,7 A52铝合金焊接接头表面的塑性变形层最厚处可达20μm左右,形成了具有大致平行于焊接接头表面择优取向的形变织构。沿厚度方向1.5 mm内,热影响区的硬度最高可达162HV,焊缝区的最高硬度为113HV,相比之前提高了21.5%,表层的耐磨性得到较为明显的提高。

ABSTRACT:Objective To study the influence of ultrasonic impact treatment on microstructure and properties of surface layer of 7A52 alumium alloy welded joint. Methods 7A52 aluminum alloy was welded by double wire MIG welding method. The welded joint was full impacted by UIT-125 ultrasonic impact treatment equipment. Microstructure of the welded joint was observed and ana-lyzed by metalloscope. The mechanical properties of welded joint were tested and studied by microhardness tester and wear testing machine. Results After ultrasonic impact treatment, continuous, uniform and smooth transition arc was formed in weld toe. The stress concentration of welded joints was alleviated. The thickness of surface deformation could reach 25 μm in heat affected zone and 15 μm in base metal. The surface 7A52 aluminum alloy welded joint by ultrasonic impact treatment equipment was obviously strengthened. Denser plastic deformation layer was induced. Surficial grains were refined. The microhardness and wear resistance were significantly increased. Conclusion After UIT, the maximum thickness of surface layer of 7A52 aluminum alloy welded Joint was about 20 μm, and the deformation texture with preferred oriention was formed and parallel to surface of welded joint. Along the thickness direction within 1. 5 mm, the maximum microhardness was 162HV in heat affected zone of the weld zone, 113HV in the weld zone, which were improved by 21. 5% comparing to these without treatment. Moreover, the wear resistance of the surface lay-er were obviously improved.