本文選題：鈦合金激光焊/超塑成形 + 淬火處理��； 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：焊接/超塑性成形組合技術(shù)在鈦合金多層空心輕量化結(jié)構(gòu)方面有著極大的優(yōu)勢。目前在焊接/超塑性成形運用較為成熟的焊接方法為擴(kuò)散連接/超塑性成形(SPF/DB),但擴(kuò)散連接/超塑性成形(SPF/DB)還存在一定的缺陷,如零件生產(chǎn)效率低、零件結(jié)構(gòu)設(shè)計和制造的靈活性差等問題。激光焊可以有效克服鈦合金擴(kuò)散連接困難,形成性能良好的接頭,但激光焊/超塑成形技術(shù)在變形后出現(xiàn)頸縮和組織不均勻現(xiàn)象,這將嚴(yán)重影響零件的性能。所以改善激光焊超塑性變形接頭變形均勻性和組織均勻性是激光焊/超塑成形技術(shù)突破的關(guān)鍵,本文以TC4鈦合金激光焊接接頭為研究對象,研究淬火處理對TC4鈦合金激光焊超塑變形的組織均勻性和拉伸均勻性進(jìn)行了研究,得出以下結(jié)論:在1000℃溫度下淬火時,接頭各區(qū)域為β相,母材與焊縫β相尺寸之比為1.2,顯微硬度差值為10HV,淬火處理可以改善TC4鈦合金激光焊接接頭組織狀態(tài),提高焊接接頭均勻性,隨著淬火溫度的升高,接頭整體組織均勻性增強(qiáng):當(dāng)淬火處理960℃~1000℃,焊接接頭在超塑性變形過程中,接頭峰值流變應(yīng)力15MPa~60MPa之間,延伸率在178.362%~581.733%之間。在相同變形條件下,隨著淬火溫度的升高,接頭應(yīng)力應(yīng)變曲線上移;焊接接頭峰值流變應(yīng)力隨著淬火溫度的升高而增大,隨著變形溫度的升高而降低,隨著應(yīng)變速率的升高而增加;焊接接頭的延伸率隨含淬火溫度的增大而減小,隨變形溫度的升高而增大,隨應(yīng)變速率的增大而減小。通過金相顯微組織觀察發(fā)現(xiàn),淬火處理可以提高焊接接頭各區(qū)域變形協(xié)調(diào)性,緩解焊接接頭超塑性變形后接頭出現(xiàn)頸縮與組織不均勻的問題。焊接接頭超塑性變形初期,焊縫與母材組織由細(xì)小的針狀組織轉(zhuǎn)變?yōu)槠瑢咏M織,超塑性變形機(jī)制以軟化作用和動態(tài)再結(jié)晶為主;接頭超塑性變形后期,片層組織持續(xù)長大,相互擠壓斷裂形成不規(guī)則組織與等軸狀組織,變形協(xié)調(diào)機(jī)制以動態(tài)再結(jié)晶與球化作用為主。焊接接頭超塑性變形后,接頭整體組織為不規(guī)則組織與等軸狀組織,焊接接頭組織均勻化程度增強(qiáng)。本文引入組織均勻性系數(shù)M和變形均勻性系數(shù)K來表征焊接接頭均勻化程度,隨著淬火溫度的升高,組織均勻性系數(shù)M與變形均勻性系數(shù)K增大,接頭均勻化程度升高;在相同的淬火溫度下,變形溫度的升高或應(yīng)變速率的降低均會使接頭均勻化程度升高,在淬火溫度1000℃,變形溫度940℃,應(yīng)變速率10-4s-1的條件下,接頭拉伸均勻性系數(shù)值為0.9269和組織均勻性系數(shù)值為0.66134。
[Abstract]:Welding / superplastic forming technology has great advantages in titanium alloy multilayer hollow lightweight structure. At present, the more mature welding method used in welding / superplastic forming is diffusion bonding / superplastic forming (SPF / DBN), but there are still some defects in diffusion bonding / superplastic forming (SPF / DBB), such as low production efficiency of parts. The flexibility of structural design and manufacture of parts is poor. Laser welding can effectively overcome the difficulty of diffusion bonding of titanium alloy and form the joints with good properties. However, the necking and uneven microstructure of laser welding / superplastic forming technology after deformation will seriously affect the performance of the parts. Therefore, improving the deformation uniformity and microstructure uniformity of laser welded superplastic deformation joint is the key to breakthrough of laser welding / superplastic forming technology. In this paper, the TC4 titanium alloy laser welded joint is taken as the research object. The microstructure homogeneity and tensile uniformity of superplastic deformation of TC4 titanium alloy laser welding were studied by quenching treatment. The following conclusions were obtained: when quenched at 1000 鈩，

本文編號：1789588