發(fā)布時間：2018-11-02 19:52

【摘要】：鋁/鎂、鋁/銅復(fù)合構(gòu)件因其性能互補(bǔ)優(yōu)勢在諸多工業(yè)領(lǐng)域具有廣泛的應(yīng)用前景,然而由于異種金屬物理、化學(xué)和物理冶金性能的差異,難以獲得力學(xué)性能可靠和耐腐蝕性良好的焊接接頭,異種金屬焊接工藝制約了這類結(jié)構(gòu)件的發(fā)展。本文首先在50～100A電流條件下對5052鋁合金/AZ31B鎂合金進(jìn)行交流TIG焊接,在優(yōu)化焊接電流參數(shù)的基礎(chǔ)上,研究焊絲材料對接頭組織和力學(xué)性能的影響;其次采用固相擴(kuò)散焊和瞬間液相擴(kuò)散焊對5052鋁合金/銅進(jìn)行連接,研究焊接溫度和保溫時間對接頭界面擴(kuò)散層厚度、顯微組織和力學(xué)性能的影響;最后對這兩種異種金屬焊接接頭在3.5%NaCl溶液中進(jìn)行浸泡腐蝕和極化曲線測試,研究接頭的耐蝕性。對于鋁合金/鎂合金交流TIG焊,在焊接電流為75～80A、焊接速度為350mm/min的條件下,可獲得焊縫成形良好的焊接接頭。焊絲材料顯著影響焊縫的組織組成和接頭的抗拉強(qiáng)度。與不填充焊絲的焊縫相比,填充AZ31B鎂合金焊絲的焊縫中析出大量細(xì)小的顆粒狀α-Mg初生相,(α-Mg+Mg_(17)Al_(12))共晶體量減少,接頭強(qiáng)度為20MPa,提高了25%;填充5052鋁合金焊絲后,Mg_(17)Al_(12)初生相由胞狀晶轉(zhuǎn)變?yōu)闃渲?且(α-Mg+Mg_(17)Al_(12))共晶體量顯著減少,接頭強(qiáng)度為5MPa,降低了 69%。固相擴(kuò)散焊和瞬間液相擴(kuò)散焊均可實(shí)現(xiàn)鋁合金/銅的有效連接,得到完整的焊接接頭。在480℃、120min條件下得到的固相擴(kuò)散焊接頭組織呈層狀分布,從鋁側(cè)至側(cè)銅依次為Al2Cu、Cu_(12)Al_9和Cu9A14,硬度值依次為264HV、170HV和138HV。隨著溫度升高和保溫時間延長,Cu9A14和Al2Cu化合物層厚度顯著增加。在570℃、20min條件下得到的瞬間液相擴(kuò)散焊接頭組織致密,接頭界面反應(yīng)區(qū)包括寬大的(α-Al+Al2Cu)共晶體區(qū)和由Cu_9Al_4、Cu_(12)Al_9和Al2Cu組成的化合物區(qū)。隨著保溫時間的延長,共晶體區(qū)的寬度顯著增加,且共晶組織的形貌由層片狀轉(zhuǎn)變?yōu)榘魻詈途栈�。浸泡腐蝕實(shí)驗(yàn)表明,鋁合金/鎂合金TIG焊接頭的焊縫區(qū)和母材區(qū)呈現(xiàn)不同的耐蝕性,焊縫區(qū)的耐蝕性最好,鋁母材的次之,鄰近焊縫的鎂母材的最差。極化曲線分析表明,填充不同焊絲焊縫區(qū)的耐蝕性也有差異,鎂焊絲焊縫的耐蝕性最好,無焊絲的次之,鋁焊絲的最差。鋁合金/銅的固相擴(kuò)散焊接頭的耐蝕性優(yōu)于瞬間液相擴(kuò)散焊接頭,瞬間液相擴(kuò)散焊接頭界面結(jié)合區(qū)的中間區(qū)域的耐蝕性明顯優(yōu)于靠近兩側(cè)母材區(qū)域的耐蝕性。
[Abstract]:Aluminum / magnesium, aluminum / copper composite components have a wide application prospect in many industrial fields because of their complementary advantages. However, due to the differences in physical, chemical and physical metallurgical properties of dissimilar metals, It is difficult to obtain welded joints with reliable mechanical properties and good corrosion resistance. Dissimilar metal welding technology restricts the development of this kind of structural parts. In this paper, the AC TIG welding of 5052 aluminum alloy / AZ31B magnesium alloy was carried out at 50 ~ 100A current. Based on the optimization of welding current parameters, the effect of welding wire material on the microstructure and mechanical properties of the joint was studied. Secondly, 5052 aluminum alloy / copper was joined by solid phase diffusion welding and transient liquid phase diffusion welding, and the effects of welding temperature and holding time on the thickness, microstructure and mechanical properties of the interface diffusion layer were studied. Finally, the corrosion and polarization curves of the two dissimilar metal welded joints were tested in 3.5%NaCl solution to study the corrosion resistance of the joints. For the AC TIG welding of aluminum alloy / magnesium alloy, the well-formed welding joint can be obtained when the welding current is 75 ~ 80A and the welding speed is 350mm/min. The wire material significantly affects the microstructure of the weld and the tensile strength of the joint. Compared with the weld without filler wire, a large number of fine grained 偽-Mg primary phases were precipitated in the weld of AZ31B magnesium alloy filler wire, the eutectic amount of (偽-Mg Mg_ (17) Al_ (12) was reduced, and the joint strength was 20 MPA, which increased 25%. After filling 5052 aluminum alloy wire, the primary phase of Mg_ (17) Al_ (12) changed from cellular crystal to dendrite, and (偽 Mg Mg_ (17) Al_ (12) eutectic volume decreased significantly, and the joint strength was 5 MPA, which decreased 69%. Solid phase diffusion welding and transient liquid phase diffusion welding can realize the effective connection of aluminum alloy / copper and obtain the complete welding joint. The microstructure of the solids diffusion welded joints was layered at 480 鈩，

本文編號：2306793