本文選題：7A56鋁合金 + 固溶　； 參考：《北京有色金屬研究總院》2017年碩士論文

【摘要】：7A56合金是一種新型的具有高強(qiáng)高韌耐蝕特征的高合金化7xxx系鋁合金,在航空航天等領(lǐng)域有著很大的應(yīng)用潛力。本文以7A56鋁合金為研究對(duì)象,采用金相顯微鏡(OM)、掃描電鏡(SEM)、透射電鏡(TEM)等組織分析手段,并結(jié)合硬度、電導(dǎo)率、室溫拉伸、斷裂韌性、剝落腐蝕及應(yīng)力腐蝕性能測(cè)試,通過(guò)系統(tǒng)研究7A56鋁合金在固溶時(shí)效過(guò)程中組織與性能的演變規(guī)律,確定合金時(shí)效析出相與典型時(shí)效狀態(tài)強(qiáng)韌性及耐蝕性的相關(guān)性,以為新型7A56鋁合金的工業(yè)化生產(chǎn)與應(yīng)用提供實(shí)驗(yàn)基礎(chǔ)和技術(shù)支持。確定了 40mm和60mm兩種厚度規(guī)格7A56鋁合金熱軋態(tài)板材中的殘留相為AlZnMgCu相和富Fe相,其中低熔點(diǎn)AlZnMgCu相的熔化起始溫度約為474℃:與60mm厚合金板材相比,40mm厚合金板材的晶粒尺寸較小,經(jīng)470℃/4h固溶處理后,合金板材中AlZnMgCu相完全回溶,晶粒發(fā)生有一定程度的長(zhǎng)大,合金淬火態(tài)電導(dǎo)率為15.6～15.7 MS/m,峰時(shí)效態(tài)硬度為204～206 HV。研究了 40mm厚7A56鋁合金板材單級(jí)、雙級(jí)與三級(jí)時(shí)效過(guò)程中的析出行為,經(jīng)單級(jí)時(shí)效處理后,合金晶內(nèi)析出相主要以η'相和GPⅡ區(qū)為主,尺寸分布范圍為1～9nm,晶界析出相多呈連續(xù)分布狀態(tài);經(jīng)雙級(jí)時(shí)效處理后,晶內(nèi)析出相尺寸明顯增大至20nm,并出現(xiàn)部分η相,晶界析出相多呈斷續(xù)分布狀態(tài),存在明顯的晶界無(wú)析出帶;經(jīng)三級(jí)時(shí)效處理后,晶內(nèi)析出相主要以η'相和GPⅡ區(qū)為主,尺寸為2～15nm,與T6峰時(shí)效態(tài)組織相似,晶界析出相多呈斷續(xù)分布,具有明顯的晶界無(wú)析出帶,與雙級(jí)時(shí)效態(tài)組織相似。隨著時(shí)效程度的增加,即時(shí)效溫度的提高和時(shí)效時(shí)間的延長(zhǎng),合金的硬度和強(qiáng)度均呈先增加后減小的趨勢(shì),電導(dǎo)率呈增加的趨勢(shì)。分析了典型時(shí)效狀態(tài)下析出相與合金強(qiáng)度性能、斷裂韌性及耐腐蝕性能的相關(guān)性。早期時(shí)效后合金中以η'相和GPⅡ區(qū)為主的晶內(nèi)析出相尺寸較小且體積分?jǐn)?shù)較大,有利于提高合金的強(qiáng)度,過(guò)時(shí)效階段晶內(nèi)析出相發(fā)生粗化,使合金強(qiáng)度降低。連續(xù)分布的晶界析出相易成為裂紋擴(kuò)展的有利途徑、以及連續(xù)的陽(yáng)極腐蝕通道,降低合金的斷裂韌性及耐腐蝕性能,而粗化并呈斷續(xù)分布的晶界析出相有利于提高合金的斷裂韌性及耐腐蝕性能。經(jīng)120℃/8h+175℃/140min+120℃/24h時(shí)效處理后,7A56合金中晶內(nèi)析出相以η'相和GPⅡ區(qū)為主,尺寸約為2～11nm,晶界析出相呈斷續(xù)分布且明顯粗化,合金板材表現(xiàn)出較好的綜合性能,其抗拉強(qiáng)度、屈服強(qiáng)度、延伸率和電導(dǎo)率分別達(dá)到637MPa、617MPa、11.6%和 22.5MS/m,平面應(yīng)變斷裂韌性(Kic)為 40.1MPa·m1/2,剝落腐蝕等級(jí)為EB,應(yīng)力腐蝕臨界強(qiáng)度因子(KISCC)為44.2MPa·m1/2。
[Abstract]:7A56 alloy is a new kind of high alloyed 7xxx alloy with high strength and high toughness and corrosion resistance. It has great application potential in aerospace and other fields. In this paper, the microstructure of 7A56 aluminum alloy was studied by means of metallographic microscope, scanning electron microscope (SEM) and transmission electron microscopy (TEM). Hardness, electrical conductivity, room temperature tensile strength, fracture toughness, exfoliation corrosion and stress corrosion resistance were measured. The evolution law of microstructure and properties of 7A56 aluminum alloy during solution aging was studied systematically, and the correlation between aging precipitation phase and strength, toughness and corrosion resistance of aging alloy was determined. It provides experimental basis and technical support for industrial production and application of new 7A56 aluminum alloy. The residual phases in hot-rolled 7A56 aluminum alloy sheet with 40mm and 60mm thickness specifications are AlZnMgCu phase and Fe-rich phase. The initial melting temperature of low melting point AlZnMgCu phase is about 474 鈩，

本文編號(hào)：1989522