本文選題：表面活化處理 + 接觸反應(yīng)釬焊　； 參考：《哈爾濱工業(yè)大學(xué)》2017年碩士論文

【摘要】：鋁合金因具有輕質(zhì)、高比強度、優(yōu)良的導(dǎo)熱導(dǎo)電性、耐腐蝕性及良好的材料加工能力而廣泛應(yīng)用于航空航天領(lǐng)域。但鋁合金表面氧化膜會對鋁合金的釬焊過程產(chǎn)生不利的影響,導(dǎo)致釬焊效果較差。本論文結(jié)合離子轟擊去膜及表面改性和磁控濺射鍍Cu層,提出表面活化輔助鋁合金釬焊連接方法并實現(xiàn)鋁合金的釬焊連接,研究了表面活化處理對鋁合金基體表面氧化膜及表面狀態(tài)的影響,對比分析表面活化處理對釬焊接頭界面組織及剪切強度的影響,系統(tǒng)研究了釬焊溫度和鍍層厚度對接頭界面組織和力學(xué)性能的影響,綜合分析接頭界面組織、晶粒形貌尺寸與接頭力學(xué)性能三者之間的相互關(guān)系,對釬焊接頭進行固溶+T6峰時效的焊后熱處理,探究焊后熱處理對釬焊接頭界面組織、晶粒形貌尺寸和力學(xué)性能的影響。離子轟擊可有效地消除鋁合金基體表面的氧化膜,并改變基體表面組織及應(yīng)力分布狀態(tài),另外鍍Cu層與離子轟擊后的基體表面之間緊密結(jié)合,且結(jié)合界面存在著原子擴散過渡層,最終實現(xiàn)了鋁合金的基體表面活化。通過對比試驗發(fā)現(xiàn),表面活化處理有效地消除了釬焊接頭中殘余氧化膜對原子擴散及接頭組織的不利影響,促進了釬焊接頭的形成和接頭中的原子擴散,并改善釬焊接頭界面組織,提高了釬焊接頭的力學(xué)性能,最終獲得了冶金結(jié)合良好且無缺陷的釬焊接頭。當(dāng)釬焊溫度為600°C時,鍍Cu層厚度分別為20μm和5μm的表面活化輔助釬焊接頭均達到最大剪切強度42.2MPa和50.7MPa,但釬焊溫度升高到610°C時,釬焊接頭中因存在異常粗大的晶粒而導(dǎo)致接頭剪切強度急劇下降。因此認為釬焊溫度的提高一方面增大接頭成分均勻化程度,有利于接頭力學(xué)性能的提高;另一方面則會導(dǎo)致接頭晶粒逐漸長大粗化,不利于接頭的力學(xué)性能。在釬焊過程中,AlCu共晶液相的晶界滲透現(xiàn)象導(dǎo)致晶界的結(jié)合強度減弱,基體晶粒沿晶界剝落進入共晶液相中并逐漸溶解。焊后熱處理進一步顯著降低了釬縫中的金屬間化合物,提高了接頭成分均勻化程度,而且釬焊接頭發(fā)生晶粒的再結(jié)晶現(xiàn)象,接頭晶粒形貌尺寸發(fā)生明顯變化,由原始的條形纖維態(tài)晶粒轉(zhuǎn)變?yōu)閴K狀的等軸晶粒并長大,接頭晶粒相對細化,故使得釬焊接頭的力學(xué)性能進一步提高,接頭剪切強度的增幅最高可達47%,并且接頭的斷裂方式由脆性斷裂轉(zhuǎn)變?yōu)轫g性斷裂。
[Abstract]:Aluminum alloy is widely used in aerospace field because of its light weight, high specific strength, excellent thermal conductivity, corrosion resistance and good material processing ability. However, the oxide film on the surface of aluminum alloy will adversely affect the brazing process of aluminum alloy, resulting in poor brazing effect. Combined with ion bombardment, surface modification and magnetron sputtering of Cu layer, the brazing bonding method of surface activated aluminum alloy was proposed and the brazing connection of aluminum alloy was realized. The effect of surface activation treatment on oxide film and surface state of aluminum alloy substrate was studied. The effect of surface activation treatment on the interface structure and shear strength of brazed joint was compared and analyzed. The effects of brazing temperature and coating thickness on the interfacial microstructure and mechanical properties of the joints were systematically studied. The effect of post-weld heat treatment on interface microstructure, grain morphology and mechanical properties of brazed joints was investigated. Ion bombardment can effectively eliminate the oxide film on the surface of aluminum alloy, and change the structure and stress distribution of the substrate. In addition, the Cu coating is tightly bonded to the substrate surface after ion bombardment. There is an atomic diffusion transition layer at the interface, and finally the substrate surface activation of aluminum alloy is realized. It is found that the surface activation treatment can effectively eliminate the negative effects of residual oxide film on the atomic diffusion and the microstructure of brazed joints, and promote the formation of brazed joints and the diffusion of atoms in the joints. The interface structure of brazed joints was improved and the mechanical properties of brazed joints were improved. Finally, the brazed joints with good metallurgical bonding and no defects were obtained. When the brazing temperature is 600 擄C, the surface activated brazing joints with Cu coating thickness of 20 渭 m and 5 渭 m respectively reach the maximum shear strength of 42.2 MPA and 50.7 MPA, but the brazing temperature increases to 610 擄C. The shearing strength of brazed joints decreases sharply due to the existence of coarse grains. Therefore, it is considered that the increase of brazing temperature is beneficial to the improvement of the mechanical properties of the joints by increasing the homogenization degree of the joint composition, on the other hand, it will lead to the grain growth and coarsening of the joints, which is not conducive to the mechanical properties of the joints. During the brazing process, the grain boundary permeability of AlCu eutectic liquid phase decreases and the matrix grains flake along the grain boundary into eutectic liquid phase and dissolve gradually. The intermetallic compound in brazing seam was significantly reduced by post-welding heat treatment, and the homogenization degree of joint composition was increased, and the recrystallization of brazing joint occurred, and the morphology and size of joint grain changed obviously. The mechanical properties of brazed joints are further improved because of the transformation from the original stripe fibrous grains to the block equiaxed grains and the relatively fine grain size of the joints. The maximum increase of shear strength of the joint is 47 and the fracture mode of the joint is changed from brittle fracture to ductile fracture.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG457.14

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