【摘要】：追求更高的強(qiáng)度級(jí)別及更佳的綜合性能是7xxx系鋁合金永恒的發(fā)展主題,提高其合金化程度已成為7xxx系鋁合金成分設(shè)計(jì)的主要方向。然而,高合金化會(huì)直接增加7xxx系鋁合金的淬火敏感性,影響新型高合金化7xxx系鋁合金在航空航天等領(lǐng)域厚截面整體式構(gòu)件制造中的應(yīng)用。本文結(jié)合直接淬火試驗(yàn)、末端淬火試驗(yàn)和分級(jí)淬火試驗(yàn),對(duì)比分析了新型高合金化7xxx系鋁合金過飽和固溶體的穩(wěn)定性和脫溶析出行為,系統(tǒng)研究了主合金化元素Mg、Cu、Zn以及微合金化元素Zr的含量對(duì)合金淬火敏感性的影響規(guī)律,為新型高合金化7xxx系鋁合金的生產(chǎn)與應(yīng)用提供技術(shù)支撐。通過對(duì)殘留相回溶及組織過燒情況的分析,確定了合金適宜的固溶制度為470～472℃/6h。采用直接淬火試驗(yàn)結(jié)合XRD精確測定合金晶格常數(shù)研究了合金過飽和固溶體的穩(wěn)定性,研究發(fā)現(xiàn),升高M(jìn)g、Zn、Zr含量會(huì)使合金固溶體晶格常數(shù)增大,升高Cu含量會(huì)使合金固溶體晶格常數(shù)減小,其中Cu元素對(duì)合金晶格畸變的影響程度最大;Mg、Cu、Zn、Zr含量升高均會(huì)導(dǎo)致合金過飽和固溶體的穩(wěn)定性下降,在同等原子量添加時(shí),Cu元素的影響作用更明顯。研究了末端淬火試驗(yàn)過程中合金的電導(dǎo)率和硬度變化、淬透深度及脫溶析出行為。隨著淬火冷卻速率降低,合金的淬火態(tài)電導(dǎo)率增大,時(shí)效態(tài)硬度減小;本試驗(yàn)合金的淬透深度約為40～75mm,臨界冷卻速率為2.12～4.78K/s。升高M(jìn)g、Cu、Zn、Zr含量均會(huì)使合金的電導(dǎo)率及硬度變化總幅度增大、淬透深度減小,會(huì)加劇末端淬火過程中固溶體脫溶析出的趨勢,在晶界上優(yōu)先脫溶出長條狀的η相,并隨著淬火冷卻速率的降低而粗化;當(dāng)淬火冷卻速率降至臨界冷卻速率以下時(shí),晶內(nèi)也會(huì)發(fā)生脫溶析出,η相主要依附于Al3Zr粒子析出。研究了分級(jí)淬火試驗(yàn)過程中合金的電導(dǎo)率和硬度變化、TTP曲線及脫溶析出行為。分級(jí)淬火溫度310℃和340℃合金性能對(duì)保溫時(shí)間的響應(yīng)速度最快,延長保溫時(shí)間,合金的淬火態(tài)電導(dǎo)率呈上升趨勢,時(shí)效態(tài)硬度呈下降趨勢。本試驗(yàn)合金的鼻溫范圍為300～320℃,鼻溫孕育期范圍為0.867～3.358s。升高M(jìn)g、Cu、Zn、Zr含量均會(huì)縮短合金TTP曲線的鼻溫孕育期,會(huì)加劇分級(jí)淬火過程中固溶體脫溶析出的趨勢,在晶界上優(yōu)先脫溶出棒狀的η相,隨保溫時(shí)間的延長而粗化,并在晶內(nèi)依附于部分Al3Zr粒子脫溶析出η相;合金經(jīng)時(shí)效后,在這些粗大的η相周圍形成了一定尺寸的無沉淀析出區(qū)。綜合直接淬火試驗(yàn)、末端淬火試驗(yàn)和分級(jí)淬火試驗(yàn)結(jié)果表明,本文試驗(yàn)范圍內(nèi),升高M(jìn)g、Cu、Zn、Zr含量均會(huì)導(dǎo)致新型高合金化7xxx系鋁合金過飽和固溶體的穩(wěn)定性下降,淬火敏感性增加,其中Cu、Mg含量的影響更為顯著。
[Abstract]:It is the eternal development theme of 7xxx series aluminum alloy to pursue higher strength level and better comprehensive properties. It has become the main direction of composition design of 7xxxx aluminum alloy to improve its alloying degree. However, high alloying will directly increase the quenching sensitivity of 7xxxx aluminum alloy, which will affect the application of the new high alloyed 7xxxx aluminum alloy in the manufacture of thick section monolithic components in aerospace and other fields. In this paper, the stability and precipitation behavior of supersaturated solid solution of a new type of high alloyed 7xxxx aluminum alloy have been compared and analyzed by means of direct quenching test, end quenching test and step quenching test. The main alloying element Mg,Cu, has been systematically studied. The influence of the content of Zn and microalloying element Zr on the quenching sensitivity of the alloy provides technical support for the production and application of a new type of high alloyed 7xxx aluminum alloy. Through the analysis of the residual phase remelting and microstructure overburning, the suitable solid solution system was determined to be 470 鈩，

本文編號(hào)：2431399