本文選題：阻燃鈦合金 + 大晶粒�。� 參考：《長安大學(xué)》2017年碩士論文

【摘要】：鈦合金因具有良好的耐熱性和高的比強度而廣泛應(yīng)用于航空航天領(lǐng)域,但常規(guī)的鈦合金部件在高溫高壓等苛刻的工作環(huán)境下,會發(fā)生嚴重的燃燒事故。針對于“鈦火”現(xiàn)象,我國在Alloy C合金的基礎(chǔ)上研發(fā)了WSTi3515S阻燃鈦合金,該合金具有良好的阻燃和綜合性能,但因其晶粒粗大,高溫變形易開裂,采用常規(guī)加工手段難以滿足產(chǎn)品性能的要求。超塑性成形技術(shù)是加工難變形材料的有效方法之一,但對于具有粗大晶粒的阻燃鈦合金超塑性的力學(xué)行為及組織演變規(guī)律尚缺乏系統(tǒng)地研究。因此,本文以熱軋退火態(tài)WSTi3515S阻燃鈦合金為研究對象,通過等溫恒應(yīng)變速率超塑拉伸試驗,對該合金在不同變形條件下的超塑性力學(xué)行為及粗大晶粒的組織演變規(guī)律進行了深入地研究。主要研究內(nèi)容和結(jié)果如下:研究了WSTi3515S阻燃鈦合金的超塑性力學(xué)行為及熱力學(xué)參數(shù)對超塑性特征的影響規(guī)律。發(fā)現(xiàn)在選定實驗范圍(溫度為800℃~920℃、應(yīng)變速率為5×10-4s-1~1×10-2s-1)內(nèi),延伸率均接近于或大于200%,具有良好的超塑性能,最大延伸率556%出現(xiàn)在920℃,5×10-4s-1條件下;揭示了大晶粒WSTi3515S阻燃鈦合金應(yīng)力-應(yīng)變曲線變化規(guī)律,且流變應(yīng)力曲線變化的實質(zhì)是加工硬化與動態(tài)軟化相互作用的結(jié)果;采用等應(yīng)變速率拉伸法測定了WSTi3515S鈦合金應(yīng)變速率敏感指數(shù)m值,在所選定應(yīng)變速率范圍內(nèi),試樣m值的平均值均大于0.3,表明合金具有良好的超塑性;基于應(yīng)力-應(yīng)變曲線,分別利用雙曲正弦型Arrhenius模型與多項式法建立WSTi3515S鈦合金本構(gòu)方程,通過誤差分析表明多項式方程精度較高;分析了WSTi3515S阻燃鈦合金在超塑性拉伸變形時的動態(tài)再結(jié)晶機制及組織演變規(guī)律。發(fā)現(xiàn)原始大晶粒被拉長壓扁,在晶界處發(fā)生動態(tài)再結(jié)晶,原始組織得到細化,隨著溫度的升高或者應(yīng)變速率的降低,再結(jié)晶晶粒不斷長大,顯微組織呈等軸狀且均勻分布;在高應(yīng)變速率(≥5×10-3s-1)及低溫(≤840℃)時發(fā)生動態(tài)再結(jié)晶,主要機制為不連續(xù)再結(jié)晶(DDRX)。在低應(yīng)變速率(≤1×10-3s-1)及高溫(≥880℃)時發(fā)生動態(tài)再結(jié)晶,主要機制為連續(xù)動態(tài)再結(jié)晶(CDRX)。但在不同條件下發(fā)生動態(tài)再結(jié)晶過程均伴隨粒子刺激形核(PSN)。揭示了不同變形條件對動態(tài)再結(jié)晶平均晶粒大小及體積分數(shù)的影響規(guī)律。結(jié)果表明,隨著變形溫度的升高或者應(yīng)變速率的降低,動態(tài)再結(jié)晶平均晶粒大小和體積分數(shù)均增大;基于Avrami模型,分別建立了動態(tài)再結(jié)晶臨界應(yīng)變模型和動態(tài)再結(jié)晶體積分數(shù)模型,動態(tài)再結(jié)晶臨界應(yīng)變模型為,動態(tài)再結(jié)晶體積分數(shù)模型為。
[Abstract]:Titanium alloy is widely used in aerospace field because of its good heat resistance and high specific strength. However, the conventional titanium alloy parts will occur serious combustion accidents under harsh working conditions such as high temperature and high pressure. In view of the phenomenon of "titanium fire", the flame retardant titanium alloy WSTi3515S was developed in China on the basis of Alloy C alloy. The alloy has good flame retardancy and comprehensive properties, but because of its coarse grain size, it is easy to crack during high temperature deformation. It is difficult to meet the requirements of product performance by conventional processing methods. Superplastic forming technology is one of the effective methods for processing refractory materials, but the mechanical behavior and microstructure evolution of flame retardant titanium alloys with coarse grain are not studied systematically. Therefore, the hot rolled annealed WSTi3515S flame retardant titanium alloy was studied by isothermal constant strain rate superplastic tensile test. The superplastic mechanical behavior and microstructure evolution of the alloy under different deformation conditions were studied. The main contents and results are as follows: the superplastic mechanical behavior of WSTi3515S flame-retardant titanium alloy and the influence of thermodynamic parameters on superplasticity were studied. It is found that in the selected experimental range (temperature 800 鈩，

本文編號：1983101