本文關(guān)鍵詞：TC4-DT鈦合金分步超塑性成形技術(shù)研究　出處：《南昌航空大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： TC4-DT鈦合金 分步超塑性 等溫鍛造 顯微組織 力學(xué)性能

【摘要】：TC4-DT鈦合金是我國自主研發(fā)的新型中強(qiáng)度、高損傷容限型α+β兩相鈦合金,作為重要的結(jié)構(gòu)材料應(yīng)用在航空航天領(lǐng)域。本文以未經(jīng)特殊細(xì)化的TC4-DT鈦合金為研究對(duì)象,通過對(duì)該合金進(jìn)行分步超塑性拉伸實(shí)驗(yàn)和分步超塑性等溫鍛造實(shí)驗(yàn),研究了不同實(shí)驗(yàn)參數(shù)下的熱變形行為和顯微組織演變規(guī)律,并對(duì)超塑性等溫鍛件在兩相區(qū)進(jìn)行三重?zé)崽幚?對(duì)熱處理后鍛件進(jìn)行室溫力學(xué)性能測(cè)試,以期為大型復(fù)雜航空結(jié)構(gòu)承力件的等溫鍛造成形提供相關(guān)技術(shù)參數(shù)及實(shí)驗(yàn)依據(jù)。對(duì)TC4-DT鈦合金提出的分步超塑性拉伸成形法,即將不同溫度條件下的常規(guī)恒應(yīng)變速率超塑性成形分為兩步,待第一步超塑性拉伸到達(dá)設(shè)定的預(yù)應(yīng)變量并保溫一段時(shí)間后,再進(jìn)行第二步超塑性拉伸。實(shí)驗(yàn)表明:在溫度為860~950℃,應(yīng)變速率為3.3×10-4~1.0×10-2 s~(-1),預(yù)應(yīng)變量為20%~80%,間隙保溫時(shí)間為5~30 min條件下,TC4-DT鈦合金均表現(xiàn)出良好的超塑性(305.93%~506.67%)。當(dāng)實(shí)驗(yàn)條件是變形溫度為890℃,預(yù)應(yīng)變量為50%,間隙保溫時(shí)間為10 min,第一步和第二步應(yīng)變速率均為3.3×10-4 s~(-1)時(shí),TC4-DT鈦合金表現(xiàn)出最佳的超塑性(506.67%)。真實(shí)應(yīng)力-應(yīng)變曲線顯示,第二步的應(yīng)力明顯小于第一步結(jié)束時(shí)的應(yīng)力,第一步變形對(duì)該合金產(chǎn)生一定的軟化作用。顯微組織顯示,動(dòng)態(tài)再結(jié)晶一直伴隨著分步超塑性成形過程,靜態(tài)再結(jié)晶發(fā)生在間隙保溫時(shí)間。再結(jié)晶行為的發(fā)生為超塑性成形提供了細(xì)小等軸組織,有利于該合金超塑性的提高。對(duì)TC4-DT鈦合金在兩相區(qū)進(jìn)行超塑性等溫鍛造實(shí)驗(yàn),并對(duì)鍛件在兩相區(qū)進(jìn)行三重?zé)崽幚?通過對(duì)其組織與性能的研究,提出了分步超塑性等溫鍛造成形工藝,即將不同溫度條件下的超塑性等溫鍛造成形分為兩步,待第一步達(dá)到設(shè)定的壓縮量并保溫一段時(shí)間后,再進(jìn)行第二步超塑性等溫鍛造成形。實(shí)驗(yàn)表明:溫度相同時(shí),分步超塑性等溫鍛造各步結(jié)束時(shí)的鍛造壓力均小于一步超塑性等溫鍛造結(jié)束時(shí)的鍛造壓力,說明分步超塑性等溫鍛造可以有效地降低一步等溫鍛造壓力。在相同變形溫度條件下,分步超塑性等溫鍛件的α相含量比一步超塑性等溫鍛件的α相含量低,條狀α相含量增多,且溫度越高,這種趨勢(shì)越明顯;不同超塑性等溫鍛造工藝下的鍛件經(jīng)過960℃/1h WQ+920℃/1h WQ+820℃/1.5h AC三重?zé)崽幚砗?均可以得到不同編織程度的網(wǎng)籃組織,編織程度越好,強(qiáng)度越高;890℃時(shí)的分步超塑性等溫鍛件和920℃時(shí)的一步超塑性等溫鍛件,經(jīng)過960℃/1h WQ+920℃/1h WQ+820℃/1.5h AC三重?zé)崽幚砗?可以獲得比較好的強(qiáng)度-塑性-沖擊韌性綜合性能匹配。
[Abstract]:TC4-DT titanium alloy is a new type of medium strength, high damage tolerance 偽 尾 two-phase titanium alloy developed independently in China. As an important structural material applied in the field of aerospace. In this paper, TC4-DT titanium alloy without special refinement as the research object. The thermal deformation behavior and microstructure evolution of the alloy under different experimental parameters were studied by means of stepwise superplastic tensile test and stepwise superplastic isothermal forging experiment. The superplastic isothermal forgings were triple-heat treated in the two-phase region, and the mechanical properties were tested at room temperature. In order to provide relevant technical parameters and experimental basis for isothermal forging of bearing parts of large complex aeronautical structure, a stepwise superplastic tensile forming method for TC4-DT titanium alloy was proposed. The conventional constant strain rate superplastic forming under different temperature conditions is divided into two steps. After the first step of superplastic stretching reaches the preset strain variable and holds for a period of time. The experimental results show that the strain rate is 3.3 脳 10 ~ (-4) 渭 m ~ (-1) and the strain rate is 3.3 脳 10 ~ (-4) (1.0 脳 10 ~ (-2) sm ~ (-1)) at the temperature of 860 ~ (-950) 鈩，

本文編號(hào)：1421877