本文選題：TC4鈦合金　切入點：超塑性　出處：《南昌大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：TC4鈦合金一般具有α+β兩相,因具有塑性好、強度高、耐熱性和耐腐蝕性好等特點,在航空、艦船、化工等領(lǐng)域廣泛應(yīng)用。鈦合金超塑性成形和傳統(tǒng)加工相比,其少或無切削加工,變形抗力小,能夠成形尺寸精度高、組織致密的復(fù)雜零件。因而,探索鈦合金新的超塑性工藝具有重要的理論意義和應(yīng)用價值。本文以2mm厚的TC4鈦合金板材為原料對TC4鈦合金的超塑性進行了研究。首先,對TC4鈦合金板材進行熱處理,通過力學(xué)性能分析,得到最佳熱處理工藝參數(shù);接著對熱處理后的試樣進行恒應(yīng)變速率和應(yīng)變誘發(fā)高溫拉伸試驗,獲得試樣延伸率。應(yīng)變誘發(fā)試驗是以恒應(yīng)變速率將試樣拉伸到預(yù)應(yīng)變量后,卸載保溫10min,再以同一應(yīng)變速率拉伸至斷裂。該方法對提高TC4合金超塑性效果顯著,工藝較為簡單,更適合在工業(yè)生產(chǎn)中應(yīng)用。通過光學(xué)顯微鏡、掃描電子顯微鏡等設(shè)備對試樣斷口進行觀察分析,探索TC4鈦合金超塑性變形力學(xué)行為、變形過程顯微組織演變、變形機制和斷裂機制。本文主要結(jié)論有:(1).TC4鈦合金最佳熱處理參數(shù)為加熱溫度820℃、保溫時間為1h,此時超塑性最好。(2).原TC4板材晶粒尺寸為1.46μm,經(jīng)熱處理后晶粒尺寸為2.41μm。在加熱溫度850℃、應(yīng)變速率1×10-3s-1條件下恒應(yīng)變速率拉伸,超塑性最好,延伸率可達901%。(3).應(yīng)變誘發(fā)試驗在預(yù)應(yīng)變量1.5時,應(yīng)變速率5×10-4s-1、加熱溫度850℃條件下,超塑性最好,延伸率可達1270.8%。(4).從試樣拉伸前后顯微組織和真實應(yīng)力-應(yīng)變曲線得出,TC4鈦合金超塑性變形機制為晶界滑動、組織動態(tài)回復(fù)和動態(tài)再結(jié)晶。(5).斷口形貌圖呈現(xiàn)出典型的韌性斷裂特征,剪切帶、韌窩斷口、脈狀花樣,因此表明TC4鈦合金具有良好的塑性。
[Abstract]:TC4 titanium alloy is widely used in aviation, ship and chemical industry because of its good plasticity, high strength, heat resistance and corrosion resistance. It has little or no cutting, low deformation resistance, high dimensional precision and compact structure of complex parts. It is of great theoretical significance and practical value to explore the new superplastic process of titanium alloy. In this paper, the superplasticity of TC4 titanium alloy is studied by using 2mm thick TC4 titanium alloy sheet as raw material. Firstly, the heat treatment of TC4 titanium alloy sheet is carried out. Through the analysis of mechanical properties, the optimum heat treatment process parameters were obtained, and the constant strain rate and strain induced high temperature tensile tests were carried out on the samples after heat treatment. The elongation of the specimen was obtained. The strain induced test was carried out after drawing the specimen to a prestrain at a constant strain rate, then unloaded for 10 min and then stretched to fracture at the same strain rate. This method has a remarkable effect on improving the superplasticity of TC4 alloy, and the process is relatively simple. By means of optical microscope, scanning electron microscope and other equipment, the fracture surface of the specimen was observed and analyzed, and the mechanical behavior of superplastic deformation and microstructure evolution of TC4 titanium alloy were explored. Deformation mechanism and fracture mechanism. In this paper, it is concluded that the optimum heat treatment parameters of TC4 titanium alloy are heating temperature 820 鈩，

本文編號：1612669