(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長沙 410083；
2. 中南大學(xué) 有色金屬材料科學(xué)與工程教育部重點(diǎn)實(shí)驗(yàn)室，長沙 410083)
摘 要: 通過熱壓縮模擬實(shí)驗(yàn)研究熱軋態(tài)2050鋁鋰合金在340~500 ℃、0.001~10 s-1下的高溫塑性變形行為，分析了熱壓縮過程中的外摩擦和溫度變化對合金流變應(yīng)力的影響，并且對測量得到的流變應(yīng)力進(jìn)行了修正。基于修正流變應(yīng)力構(gòu)建了熱軋態(tài)2050鋁鋰合金的流變應(yīng)力統(tǒng)一本構(gòu)方程，包括應(yīng)變修正Arrhenius模型和Hensel-Spittel模型，同時(shí)還繪制了合金在不同應(yīng)變量下的熱加工圖，并通過金相顯微鏡觀察了不同變形條件熱壓縮試樣的晶粒形貌。結(jié)果表明：外摩擦?xí)?dǎo)致流變應(yīng)力測量值高于理想值，而絕熱溫升造成的溫度變化會(huì)導(dǎo)致流變硬化或軟化，使得流變應(yīng)力改變。統(tǒng)一本構(gòu)方程模型在擬合區(qū)間內(nèi)都具有較高的擬合性，應(yīng)變修正Arrhenius模型在穩(wěn)態(tài)流變階段的擬合程度較高，Hensel-Spittel模型能描述合金在整個(gè)熱變形過程的流變應(yīng)力變化。通過熱加工圖可以發(fā)現(xiàn)熱軋態(tài)2050鋁鋰合金最佳的加工范圍是溫度420~500 ℃、應(yīng)變速率0.001~0.003 s-1區(qū)域。流變失穩(wěn)區(qū)為溫度350~480 ℃、應(yīng)變速率3.16~10 s-1和溫度340~360 ℃、應(yīng)變速率0.1~3.16 s-1兩個(gè)區(qū)域。合金在穩(wěn)定區(qū)主要發(fā)生動(dòng)態(tài)回復(fù)和動(dòng)態(tài)再結(jié)晶，而在失穩(wěn)區(qū)主要發(fā)生局部流變。
關(guān)鍵字: 2050鋁鋰合金；Arrhenius模型；Hensel-Spittel模型；流變應(yīng)力本構(gòu)方程；熱加工圖
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China）
Abstract:The hot deformation behavior of hot-rolled 2050 Al-Li alloy at 340-500 ℃ and 0.001-10 s-1 was studied by hot compression simulation experiment. The effects of friction and temperature variation on the flow stress of the alloy during the hot compression process were analyzed, and the true stress-strain curves were corrected. Based on the corrected curves, the constitutive equation of the hot-rolled 2050 Al-Li alloy was constructed, including the strain modified Arrhenius model and Hensel-Spittel model. At the same time, the processing maps of the alloy under different true strains were established. The microstructure of the hot compressed samples was observed by the optical microscope. The results show that the friction will cause the measured value of true stress to be higher than the actual stress value, and the temperature change caused by adiabatic heat will cause flow softening and decrease the true stress. The two types of constitutive equation models both fit well in the fitting interval. The strain-compensated Arrhenius model has a higher degree of mathematical fitting in the steady-state. The Hensel-Spittel model can describe the entire hot deformation process of the alloy. It can be found from the processing maps that the best processing range for the hot-rolled 2050 Al-Li alloy is within the region that the temperature ranges from 420 ℃ to 500 ℃ and the strain rate ranges from 0.001 s-1 to 0.003 s-1. The instability areas locate on two regions, there are region of temperature 350-480 ℃, strain rate 3.16-10 s-1 and region of temperature 340-360 ℃, strain rate 0.1-3.16 s-1. The alloy mainly undergoes dynamic recovery and dynamic recrystallization in the stable area, while the flow localization mainly occurs in the instability area.
Key words: 2050 Al-Li alloy; Arrhenius model; Hensel-Spittel model; flow stress constitutive equation; processing map
