本文選題：TB8鈦合金 + 超塑性��； 參考：《南昌航空大學(xué)》2017年碩士論文

【摘要】：TB8鈦合金是一種超高強(qiáng)度亞穩(wěn)態(tài)β型鈦合金,常用于制備航空、航天領(lǐng)域的結(jié)構(gòu)件。較高的β穩(wěn)定元素含量使得該合金的變形抗力較高,導(dǎo)致在塑性成形工藝的應(yīng)用中受到限制。因此,探討該合金超塑性成形技術(shù)成為解決這一問(wèn)題的有效途徑之一。本文以熱變形參數(shù)對(duì)TB8鈦合金動(dòng)態(tài)再結(jié)晶及時(shí)效析出行為的影響為切入點(diǎn),從熱變形過(guò)程中的動(dòng)態(tài)再結(jié)晶、時(shí)效析出行為等多個(gè)角度研究了TB8鈦合金超塑性行為以及超塑性變形過(guò)程中的組織演變規(guī)律。同時(shí)引入形變誘導(dǎo)超塑性拉伸法,通過(guò)形變誘導(dǎo)析出強(qiáng)化和再結(jié)晶組織優(yōu)化雙重手段有效地提高其超塑性能。通過(guò)高溫拉伸試驗(yàn)研究TB8鈦合金超塑性變形顯微組織的演變及變形條件對(duì)超塑性變形行為的影響。結(jié)果表明:在變形溫度為690℃~840℃、應(yīng)變速率為10-4s-1~10-3s-1拉伸時(shí),TB8鈦合金具有超塑性變形性能,且在750℃、10-4s-1變形條件下,延伸率最大為524.9%。變形過(guò)程中,變形軟化和加工硬化相互抵消,表現(xiàn)為傳統(tǒng)的超塑性變形穩(wěn)態(tài)流動(dòng)特征;同時(shí),變形溫度、應(yīng)變速率和變形程度對(duì)超塑性變形后的顯微組織有顯著的影響,隨著變形速率的降低,等軸β相晶粒尺寸增大;隨著變形溫度的升高,β相晶粒尺寸增大,并伴有α相到β相的轉(zhuǎn)變,但仍能保持一定的等軸度;隨著變形程度的增大,β晶界和基體彌散析出的α相越多,細(xì)小、彌散分布的α相可以抑制晶粒的過(guò)分長(zhǎng)大。采用形變誘導(dǎo)法對(duì)TB8鈦合金進(jìn)行了超塑性拉伸試驗(yàn),研究了變形溫度、預(yù)變形量和中間保溫時(shí)間對(duì)該合金超塑性性能及微觀組織演變的影響。結(jié)果表明:與恒應(yīng)變速率法拉伸相比,該方法拉伸后合金的超塑性得到大幅度地提升,變形溫度為750℃、預(yù)變形量為50%和保溫時(shí)間為20min時(shí),該合金的超塑性能最好,延伸率為796.1%。預(yù)變形階段,脫溶析出和再結(jié)晶雙重優(yōu)化作用使亞穩(wěn)態(tài)β相轉(zhuǎn)變?yōu)榧?xì)小均勻的再結(jié)晶組織,在后續(xù)變形過(guò)程中,細(xì)小彌散的α相既能抑制再結(jié)晶晶粒過(guò)分長(zhǎng)大,又能在一定程度上使再結(jié)晶組織發(fā)生應(yīng)變集中而破碎。超塑性變形后合金的微觀組織仍然保持較好的等軸狀,具有顯著的超塑性變形特征。通過(guò)對(duì)TB8鈦合金熱變形行為研究,建立了合金的動(dòng)態(tài)再結(jié)晶有關(guān)模型。分析得到隨著變形溫度的升高和應(yīng)變速率的減小,發(fā)生動(dòng)態(tài)再結(jié)晶體積分?jǐn)?shù)增加,再結(jié)晶晶粒尺寸隨之增加;而低溫和高應(yīng)變速率環(huán)境下則會(huì)延遲動(dòng)態(tài)再結(jié)晶的發(fā)生。合理控制熱變形參數(shù),可以得到均勻細(xì)小的動(dòng)態(tài)再結(jié)晶組織,提高合金的塑性變形能力,所得結(jié)論與試驗(yàn)結(jié)果相吻合。
[Abstract]:TB8 titanium alloy is a super high strength metastable 尾-titanium alloy. The high content of 尾 -stable elements makes the alloy have higher deformation resistance, which limits its application in plastic forming process. Therefore, discussing the superplastic forming technology of the alloy is one of the effective ways to solve this problem. Based on the effect of thermal deformation parameters on dynamic recrystallization and aging precipitation behavior of TB8 titanium alloy, the dynamic recrystallization during hot deformation is studied in this paper. The superplastic behavior and microstructure evolution of TB8 titanium alloy during superplastic deformation were studied from aging precipitation behavior. At the same time, the deformation induced superplastic tensile method was introduced to improve the superplasticity effectively by means of deformation induced precipitation strengthening and recrystallization microstructure optimization. The evolution of superplastic deformation microstructure of TB8 titanium alloy and the effect of deformation conditions on superplastic deformation behavior were studied by high temperature tensile test. The results show that TB8 titanium alloy has superplastic deformation property when the deformation temperature is 690 鈩，

本文編號(hào)：1988805