發(fā)布時(shí)間：2018-04-11 03:22

  本文選題：7075鋁合金 + 時(shí)效成形��； 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：在航空工業(yè)迅猛發(fā)展的當(dāng)前,對(duì)飛機(jī)整體壁板的成形提出越來越高的要求,而時(shí)效成形是飛機(jī)整體壁板類工件成形的有效方法。研究材料預(yù)變形后對(duì)時(shí)效成形件性能的影響,是對(duì)傳統(tǒng)時(shí)效成形工藝的發(fā)展和創(chuàng)新,具有重要的理論意義和工程實(shí)用價(jià)值。本文以T6態(tài)的7075鋁合金薄板為研究對(duì)象,研究了在預(yù)變形、預(yù)變形加固溶處理以及最終形變熱處理?xiàng)l件下,材料未時(shí)效態(tài)、時(shí)效態(tài)及時(shí)效成形態(tài)的力學(xué)性能及微觀組織。研究結(jié)果表明:T6態(tài)的7075鋁合金時(shí)效成形回彈率會(huì)隨預(yù)變形量的增加而減小。當(dāng)預(yù)變形量為7%時(shí)試樣回彈率達(dá)到最小,為21.02%,比預(yù)變形量為0時(shí)回彈率下降了64.88%,此時(shí)的7075鋁合金擁有良好的成形性能,但是其強(qiáng)度相比未時(shí)效態(tài)的試樣會(huì)大幅度下降。通過透射電鏡可以發(fā)現(xiàn),未時(shí)效態(tài)試樣晶內(nèi)析出相主要是由強(qiáng)化相GP區(qū)和η'相構(gòu)成,晶界析出相細(xì)小連續(xù),晶界無析出帶不明顯,經(jīng)過時(shí)效成形后,強(qiáng)化相GP區(qū)和η'大部分消失了,出現(xiàn)了粗大的η相,晶界變?yōu)閿嗬m(xù)分布,晶界析出相尺寸變大,使合金強(qiáng)度低于未時(shí)效態(tài)試樣。對(duì)T6態(tài)的7075鋁合金進(jìn)行固溶處理,其固溶處理后力學(xué)性能得到了提升,未時(shí)效態(tài)預(yù)變形量為2%的時(shí)試樣延伸率高達(dá)22.33%,比T6態(tài)母材延伸率提高了31.35%。在固溶處理的基礎(chǔ)上對(duì)合金施加預(yù)變形,最后時(shí)效成形,發(fā)現(xiàn)其回彈率也會(huì)隨預(yù)變形量的增加而減小。預(yù)變形量在7%時(shí)回彈率達(dá)到最小,為38.30%,此時(shí)試樣的成形性能也很好,且其強(qiáng)度比時(shí)效態(tài)預(yù)變形量為7%時(shí)提高了20.89%。在固溶處理→預(yù)變形→人工時(shí)效的基礎(chǔ)上,通過在預(yù)變形前加預(yù)時(shí)效,發(fā)現(xiàn)終時(shí)效、時(shí)效成形態(tài)后合金的強(qiáng)度得到了大幅度的提高。通過透射電鏡可以發(fā)現(xiàn)預(yù)時(shí)效可以為基體提供均勻分布的細(xì)小彌散相GP區(qū)和少量的η'相,而GP區(qū)會(huì)為終時(shí)效時(shí)強(qiáng)化相η'相的均勻形核提供條件,同時(shí)時(shí)效、時(shí)效成形后η'相會(huì)被球化,球化的均勻分布的η'相會(huì)使合金的力學(xué)性能得到改善。最終形變熱處理工藝下7075鋁合金時(shí)效成形回彈率也會(huì)隨試樣預(yù)變形量的增加而減小,但是最小回彈率只有62.66%,成形性能相比其他兩個(gè)工藝發(fā)生了下降,總的說來,預(yù)變形對(duì)時(shí)效成形回彈率的減小是有益的。
[Abstract]:With the rapid development of aviation industry, higher and higher requirements are put forward for the forming of aircraft integral wall plates, and aging forming is an effective method for forming aircraft integral wall panels.It is of great theoretical significance and practical value to study the effect of pre-deformation of materials on the properties of aging forming parts, which is important to the development and innovation of traditional aging forming process.In this paper, the mechanical properties and microstructure of 7075 aluminum alloy sheet in T6 state were studied under the conditions of pre-deformation, pre-deformation strengthening solution treatment and final thermomechanical treatment.The results show that the springback rate decreases with the increase of pre-deformation of 7075 aluminum alloy.When the pre-deformation is 7, the springback rate of the sample reaches the minimum (21.02), which is 64.88% lower than that of the pre-deformation 0. The 7075 aluminum alloy has good formability, but its strength will be greatly reduced compared with the unaged specimen.It can be found by TEM that the precipitated phase is mainly composed of strengthening phase GP region and 畏 'phase. The precipitated phase at grain boundary is fine and continuous, and there is no obvious precipitation band at grain boundary.Most of the GP region and 畏'of the strengthened phase disappeared, and the coarse 畏 phase appeared, the grain boundary became discontinuous distribution, and the size of precipitated phase at the grain boundary became larger, which made the strength of the alloy lower than that of the unaged sample.The mechanical properties of 7075 aluminum alloy in T6 state were improved after the solution treatment. The elongation of 7075 aluminum alloy was 22.33 when the pre-deformation of aging state was 2%, which was 31.35% higher than that of T6 base metal.On the basis of solution treatment, the alloy was pre-deformed and the springback decreased with the increase of pre-deformation.The springback rate of the sample reaches the minimum at 7 and is 38.30. The formability of the sample is also very good, and its strength is 20.89% higher than that of the aging predeformation of 7.On the basis of the artificial aging of solution treatment and pre-deformation, it is found that the strength of the alloy has been greatly improved after the final aging and aging into shape by adding pre-aging before pre-deformation.It is found by TEM that preaging can provide uniform distribution of small dispersed phase GP region and a small amount of 畏 'phase for the matrix, while GP region can provide conditions for homogeneous nucleation of the strengthened phase 畏' phase at the end of aging, and aging at the same time.After aging forming, 畏 'phase will be spheroidized, and the mechanical properties of the alloy will be improved by the uniformly distributed 畏' phase of spheroidization.Under the final thermomechanical treatment process, the springback rate of aging forming of 7075 aluminum alloy will also decrease with the increase of sample pre-deformation, but the minimum springback rate is only 62.66, and the formability of 7075 aluminum alloy decreases compared with the other two processes.Pre-deformation is beneficial to the reduction of springback.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG146.21;TG166.3

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本文編號(hào)：1734206