【作者】 胡文金；

【导师】 董红刚；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 本着经济、节能的宗旨,铝合金/钢异种金属连接结构在工业生产中受到重视。并且,应用焊接的方法实现两种金属的连接更能满足实际生产的要求。然而,常温下铝与铁极低的固溶度和物理化学性质的巨大差异,给两种金属之间的焊接带来了困难。本文通过两种途径实现了铝合金和钢的异种钨极氩弧熔钎焊连接,研究了合金元素的加入对异质接头组织和性能的影响。在碳钢表面镀锌,通过填充Al-5%Si、 Al-12%、 Al-6%Cu、 Al-10%Si-4%Cu和Zn-15%A1实芯焊丝得到铝/镀锌钢异种接头,研究Si、 Cu、 Zn等合金元素的加入对接头组织与性能的影响。通过填充Zn-15%A1和Al-12%Si药芯焊丝,进行铝合金与碳钢的直接弧焊连接。研究了Zn和Si元素对接头组织性能的影响。研究发现,随着焊缝中Si元素含量的增加,接头中金属间化合物层的厚度减小。当填充Al-12%Si焊丝时,接头抗拉强度可达136MPa,并且金属间化合物层的厚度仅约2μm。 Al-Si-Cu焊丝的加入,得到的接头化合物层的厚度要小于填充Al-Cu焊丝的接头。说明Cu元素对化合物层生长的抑制作用不如Si元素。并且,拉伸试验后,填充Al-Cu焊丝的试样断裂在金属间化合物层,而其它试样断裂在焊缝内。填充Zn-15%A1焊丝的接头金属间化合物层较厚,但是试样拉伸后却断裂在焊缝处。说明在此类接头中,焊缝内粗大的枝晶组织是最薄弱的部位。另外,在靠近界面层处,发现了较多的富锌相。填充Zn-15%A1药芯焊丝所得铝合金/碳钢接头中,金属间化合物层的厚度超过了15μm,且在焊接的过程中有一部分脱落,与焊缝金属相互扩散形成高硬度的富铁区域。而填充Al-12%Si药芯焊丝所得接头的化合物层厚度低于5μm,其中并无界面层脱落现象。然而前者的强度却要高于后者,说明Zn元素的加入,在抑制化合物层生长方面不及Si元素,却可以参加化合物层反应,改善其脆性,优化焊缝性能。另外,对两种接头分别进行了焊后热处理,由于焊接残余应力的消除,其强度均有大幅提高。更多还原

【Abstract】 The connection of aluminum alloy and steel was paid more attention in industry for the low cost and energy reducing. And, only the joining of these two metals can satisfied the requirement of the manufacture application. But it is hard to realize due to the low solution ability at normal temperature and the great difference of thermal-physical properties between aluminum and iron. This paper lap joined aluminum alloy to carbon steel successfully through two methods, coating carbon steel with zinc and using solid filler wires, arc joining aluminum alloy to carbon steel directly with flux cored filler wire. More important, the effect of alloying elements on the microstructure and mechanical properties was researched.Aluminum alloy sheets were lap joined to galvanized steel sheets by gas tungsten arc welding (GTAW) with Al-5%Si, Al-12%Si, A1-6%Cu, Al-10%Si-4%Cu and Zn-15%A1filler wires. Different amounts of Si, Cu and Zn were introduced into the weld through different filler wires. The effects of alloying elements on the microstructure in the weld and tensile strength of the resultant joint were investigated. It was found that the thickness of the intermetallic compound (IMC) layer decreased and the tensile strength of the joint increased with the increase of Si content in the weld. The thickness of the IMC layer could be controlled as thin as about2μm and the tensile strength of the dissimilar metal joint reached136MPa with Al-12%Si filler wire. Al-Si-Cu filler wire could result in thinner interfacial layer than Al-Cu filler wire, and fracture during tensile testing occurred in the weld for the former but through the intermetallic compound layer for the latter filler wire. A Zn-rich phase formed in the weld made with Zn-15%A1filler wire. Moreover, the Zn-Al filler wire also generated thick interfacial layer containing a great amount of intermetallic compounds and coarse dendrites in the weld, which led to a weak joint.The intermetallic layer of aluminum alloy/carbon steel joint with Zn-15%A1flux cored filler wire was above15μm and detached into weld during welding. An iron rich zone formed due to the diffusion between detached layer and the molten weld metal. Meanwhile, the intermetallic layer of joint with Al-12%Si flux cored filler wire was less than5μm and with no detachment. However, the tensile strength of former joint was much higher than the later. The Zn element was weaker in inhibiting the growth of intermetallic compound than Si element. But the Zn element joined the reaction of aluminum and iron, decreased the brittleness of the intermetallic layer and improved the tensile strength. Post welded heat treated was taken for both joints. Because of the releasing of stress, the tensile strength of both joints increased.更多还原