【作者】 徐东宏；

【导师】 陈彦宾；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 高强铝合金2519A是一种新型结构材料,具有较高的比强度、比刚度以及良好的加工和高低温力学性能,且在海水及盐雾环境下的抗应力腐蚀性能大大提高,在航空航天领域应用潜力极大。但2519A铝合金焊接工艺性及其接头组织性能的影响变化趋势,还未见明确的研究成果。本文针对2519A铝合金的氩弧焊、搅拌摩擦焊工艺性及其接头组织、力学性能进行了试验研究,并对焊接接头的耐腐蚀性能进行了分析。试验发现,2519A-T87铝铜合金氩弧焊接工艺性良好,优于2A12型铝合金,但较5A06铝合金焊接工艺性差。2519A铝铜合金具有焊接热裂纹倾向,焊接材料的选择应优选Al-Cu系,通过预热可降低热裂纹倾向。焊接过程需对焊接材料、焊接工艺参数严格控制才能减少焊接气孔、裂纹等缺陷的出现。2519A-T87/5A06-O异种铝合金熔焊时,焊核区凝固组织的枝晶间形成了1～10μm厚的Mg2Si与基体形成的非平衡共晶和游离状态的Al2CuMg(S相)圆形粒子。虽然焊核区是凝固组织,但仍获得了高于5A06-0态母材的硬度值,拉伸断口在5A06-O态母材侧。2519A-T87/5A06-O铝合金熔焊焊核区腐蚀主要沿枝晶间隙扩展,腐蚀的这种扩展方式会因枝晶的交叉错排特性方式而受到抑制,焊接件整体上可获得较好的耐剥落腐蚀性能。铝合金2519A-T87板材搅拌摩擦焊时,焊核区粗大的Al2Cu相与Fich-(Fe,Mn)相被破碎,且分布更加均匀。搅拌摩擦焊充分利用了基体晶粒细晶强化第二相弥散强化来提高接头的力学性能,其中热机影响区硬度值最低,约为母材的78%。而时效和固溶—时效等焊后热处理方式由于发生了复杂的机体组织和第二相析出等微结构演变,均未取得强化焊接接头力学性能的效果。铝合金2519A-T87的搅拌摩擦焊明显降低焊接头区域的耐剥落腐蚀性能,母材耐蚀等级为EB级,焊接头区域的焊接态耐蚀等级为EC+;焊后热处理会使母材与焊接头区域的耐蚀性能整体降为ED级。更多还原

【Abstract】 High-strength aluminum alloy 2519A-T87 is a kind of new structure material. This material has high specific strength highspecific stiffness, and good processability, it also has good stress corrosion resistance in severe environments such as sea, salt atmosphere. So it has great potential in the aeronautical and astronautical field. However there are no clear cut research results about the weldability of 2519A-T87 aluminum alloy and the structure of welding joint.In this paper, the argon-arc welding processibility and friction stir welding processibility of 2519A-T87 aluminum alloy, the welding joint mechanical property were researched by experiments. The decay resistances of the welding joint were analyzed.The experiments results indicated argon-arc welding processibility of 2519A-T87 aluminum alloy was good, which is better than 2A12 aluminum alloy, but was not as good as 5A06 aluminum alloy.The 2519A-T87 aluminum alloy had the tendency of welding heating crack. The welding material ought to select Al-Cu series,By warming up,the tendency of welding heating crack could be reduced.In order to reduce welding blow hole and crack,the welding material,the welding parameters were strictly controled.When aluminum alloy 2519A-T87/5A06-O were fusion welded, the gross Al2CuMg phase (S phase) round particles and unequilibrium eutectic formed by Mg2Si and matrix 1～10μm thick were come in to being between dendrites of solidification structures.Though welding nuclear area were formed by solidification structures,its hardness was higher than 5A06-O.The stretching stracture was in 5A06-O material.Aluminum alloy 2519A-T87/5A06-O welding nuclear area corrosion diffused mainly along dendrites. This corrosion diffuse way could be restrained by dendrites across arrange.The whole welding structure could obtain good decay resistance.When aluminum alloy 2519A-T87 was FSW (Friction Stir Welding), the gross Al2Cu phase and Fich-(Fe, Mn) phase iand Fich-(Fe, Mn) phase in the welding nuclear area were broken into pieces and distributed. During FSW, mechanical properties of welded joint were improved by the fine grain strengthening and second phase dispersion strengthening. At the heat reflection area, hardness value was the minimum, order of 78% of the base mental. After the post welding heat treatment, the welded joint mechanical properties weren’t improved because of the complex base tissue and the second phase precipitation structural evolution.The break away corrosion resistant of 2519A-T87 aluminum alloy FSW welded joint was reduced. The corrosion resistant degree of base mental was EB and the degree of welded joint was EC+. After the post welding heat treatment, corrosion resistant degree of base mental and welded joint was reduced to ED.更多还原