2A97/5A06异种铝合金搅拌摩擦对焊板不均匀组织及高温协调变形行为研究

Non-uniform Microstructure and High Temperature Coordinated Deformation Behavior of Friction Stir Butt-Welded 2A97/5A06 Dissimilar Aluminum Alloy Plate

摘要:

本工作围绕2A97/5A06异种铝合金搅拌摩擦对焊板不均匀组织及高温协调变形行为开展研究。对焊后接头各区域进行微观组织观察，并对接头各区域及整体高温性能开展研究。发现焊后2A97与5A06的焊核区晶粒细小，2A97侧各区域晶粒尺寸较小且基本接近，5A06侧各区域晶粒尺寸略大且差别较明显。2A97与5A06母材在430 ℃、10^–3 s^–1条件下高温性能较好，延伸率分别达到278.8%和120.6%。接头焊核区强度和延伸率分别为18.4 MPa和176.1%，均介于2A97与5A06之间，强度约为2A97母材的2倍，延伸率约为5A06母材的1.5倍，整体性能呈现出明显的叠加原理。各区域变形抗力不同，垂直焊缝拉伸时在2A97热力影响区集中变形后发生断裂，修正后流动应力略高于母材而延伸率基本接近母材。焊后各区域晶粒尺寸与流动应力符合蠕变方程规律，晶粒尺寸越细小，流动应力也会相应降低。

Abstract:

The non-uniform microstructure and high temperature coordinated deformation behavior of friction stir butt-welded 2A97/5A06 dissimilar aluminum alloy plate were studied. The microstructure of each zone in the welded joint was observed, and the high temperature mechanical properties of both individual zones and the whole joint were studied. Results show that grains in the weld nugget zone of 2A97 and 5A06 are fine. The grain sizes of various zones on the 2A97 side are small and uniform, whereas those on the 5A06 side are slightly larger and exhibits a more significant variation. Under the condition of 430 °C and 10^–3 s^–1, the 2A97 and 5A06 base metals exhibit good high temperature properties, with elongations reaching 278.8% and 120.6%, respectively. The strength and elongation of the nugget zone in the joint are 18.4 MPa and 176.1%, respectively, which are between those of 2A97 and 5A06 base metals. The strength is about 2 times higher than that of the 2A97 base metal, and the elongation is about 1.5 times higher than that of the 5A06 base metal. The overall performance follows superposition principle. Due to the varying deformation resistance of each region, fracture occurs in the thermo-mechanically affected zone on the 2A97 side after concentrated deformation during transverse tensile testing. After correction, the flow stress is slightly higher than that of the base metal and the elongation is close to that of the base metal. The grain size and flow stress of each region after welding follow the creep equation. The smaller the grain size, the lower the flow stress.