AZ31B和7075搅拌摩擦焊接头组织与力学性能研究

发布时间：2018-01-15 19:07

本文关键词：AZ31B和7075搅拌摩擦焊接头组织与力学性能研究　出处：《湖南大学》2015年硕士论文　论文类型：学位论文

【摘要】：镁合金、铝合金具有密度小、比强度高、切削加工性能优良等优点,目前广泛应用于航空航天、电器电子、高速列车、汽车、船舶等行业。搅拌摩擦焊主要用于低熔点金属及其合金的固态连接,在焊接的过程中不需要气体保护、填充焊丝、无弧光辐射、烟尘和飞溅,且焊接头内不易产生气孔、疏松和热裂纹等缺陷,焊接接头头的力学性能较好,在实际生产中其设备易于操作,便于实现自动化。本文主要研究了10mm厚AZ31B镁合金和7075铝合金板材同种合金FSW对焊,分析了在一定焊接工艺参数下焊接接头的金相显微组织、显微硬度和力学性能,并通过改变轴肩下压量分析其对焊缝质量、组织结构及接头力学性能的影响,探索其内在规律,得出以下结论：(1)分别实现了10mm厚AZ31B镁合金板材搅拌摩擦焊接对焊和10mm厚7075铝合金板材的搅拌摩擦焊接对焊,形成了外观成型良好,微观组织形态、力学性能优良的焊接接头。(2)增加轴肩下压量至1.5mm时,AZ31B镁合金FSW焊缝表面更加细密、光滑、波纹状组织更加连续,且旋转速度与焊接速度比值在28左右时增加轴肩下压量会使这种趋势更加明显。(3)AZ31B镁合金搅拌摩擦焊接头的横截面显微硬度值总体呈现出“W”字形状,沿中心线大致呈对称分布,母材区硬度约为70HV,焊缝区硬度最高值达到67HV,出现在偏离焊缝中心的后退侧焊核区。(4)轴肩下压量从0.5mm增加到1mm时,下压量大小变化对接头的抗拉强度和延伸率影响不大。而在轴肩下压量从1mm增加到1.5mm时,抗拉强度与延伸率都获得了显著的提升,在轴肩下压量d=1.5mm时达到最大,此时抗拉强度和延伸率分别为213MPa及6.87%,分别比d=0.5mm时搅拌摩擦焊接头提高了17.7%和29.4%。(5)在7075铝合金对接接头中,焊核区组织发生了完全动态再结晶,其晶粒为细小的等轴晶粒。热机械影响区前进侧的晶粒比后退侧的晶粒长,而且晶粒不规整也不均匀。热影响区的晶粒变化和热机械影响区一致。(6)对7075铝合金第二相粒子的分析结果表明：随着轴肩下压量的增加,焊核区的第二相粒子分布比母材区细小、均匀；而热机械影响区的第二相粒子将会被拉长和粗化；热影响区第二相粒子逐渐变多。
[Abstract]:Magnesium alloy, Aluminum Alloy has low density, high specific strength, good cutting performance, is widely used in aerospace, electrical and electronic, high-speed train, automobile, shipbuilding and other industries. The friction stir welding is mainly used for solid connection with low melting point metal and alloy, the welding process does not require gas protection, filling no wire, arc radiation, dust and splash, and the welding head is not easy to produce pores, porosity and hot crack defects, mechanical properties of the welding joint head is good, in the actual production of the equipment is easy to operate, easy to realize automation. This paper mainly studies the 10mm thick AZ31B magnesium alloy and Al alloy 7075 Aluminum Alloy plate FSW analysis of the butt welding, microstructure of welded joints under certain welding parameters, microhardness and mechanical properties, and by changing the shoulder press amount on the weld quality, organization structure and joint Effect of mechanical properties, explore its inherent laws, draw the following conclusions: (1) were achieved by 10mm thick AZ31B magnesium alloy friction stir welding friction stir butt welding and butt welding of 10mm thick 7075 Aluminum Alloy plate, formed the appearance of good shape, microstructure and mechanical properties of welded joint with good (2). Increase the shoulder press amount to 1.5mm, the surface of AZ31B magnesium alloy FSW weld is more dense, smooth, corrugated tissue more continuous and rotational speed and welding speed ratio increases about 28 when the shoulder press amount will make this trend more obvious. (3) the friction welding head cross section microhardness values the whole show "W" shape mixing AZ31B magnesium alloy, along the center line roughly symmetrical distribution, hardness of base metal is about 70HV, the hardness of Weld Zone reached the highest value of 67HV, appeared in the deviation from the weld center back side nuclear welding. (4) under pressure from the shoulder 0.5mm increased to 1mm, under the pressure of the size changes of tensile strength and elongation of the joint is not affected. But in the shoulder press amount increased from 1mm to 1.5mm, the tensile strength and elongation have been significantly improved, the shoulder pressure volume reached the maximum at d=1.5mm, the tensile strength and elongation rates were 213MPa and 6.87%, respectively than d=0.5mm when the friction stir welding increased by 17.7% and 29.4%. (5) in the 7075 Aluminum Alloy butt joint, organization of the nugget zone has completely dynamic recrystallization, the grain is fine equiaxed grains. The grain grain TMAZ of advancing side than the back side long and irregular grain is not uniform. The grain size change and thermal mechanical affected zone favorable heat affected. (6) the results of the second phase particles of 7075 Aluminum Alloy showed: with the increase of shoulder pressure volume, second phase particles distribution in the nugget zone than the base metal thin The second phase particles in the thermo mechanical affected zone will be elongated and coarsened, and the second phase particles in the heat affected zone gradually become more and more.

【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG453.9

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