本文選題：攪拌摩擦加工　切入點(diǎn)：超細(xì)晶鎂合金　出處：《西安建筑科技大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：AZ31鎂合金是目前使用最廣泛的變形鎂合金,研究超細(xì)晶鎂合金的塑性變形行為對(duì)鎂合金的推廣應(yīng)用具有重要的意義。本文以攪拌摩擦加工(Friction Stir Processing,FSP)制備的AZ31超細(xì)晶鎂合金為研究對(duì)象,采用納米壓痕技術(shù)探索FSP AZ31鎂合金的塑性變形行為;對(duì)FSP AZ31鎂合金進(jìn)行高溫拉伸,探索其高溫塑性變形行為。主要研究結(jié)果如下:FSP加工后的區(qū)域,不同載荷下加載過程中曲線的重復(fù)性較好,而BM區(qū)域有所波動(dòng),這與材料的組織均勻性有關(guān)。BM的最大壓入深度大于FSP各個(gè)區(qū)域。其中,母材(Basal Metal,BM)攪拌區(qū)(Stir Zone,SZ)和前進(jìn)側(cè)的熱機(jī)械影響區(qū)域(Thermo-Mechanical Affected Zone-Advancing Side,TMAZ-AS)、后退側(cè)的熱機(jī)械影響區(qū)域(Thermo-Mechanical Affected Zone-Retreating Side,TMAZ-RS)的最大深度分別為1244.9 nm,1156.6 nm、1148.3 nm和1142.8 nm。在載荷為5 mN時(shí)表現(xiàn)出較高的納米硬度,其中TMAZ-AS側(cè)的硬度值最高為1.435 GPa。隨著載荷增加,鎂合金的納米硬度值下降,表現(xiàn)出明顯的尺度效應(yīng)。在不同載荷下,FSP加工區(qū)域的楊氏模量保持不變,而BM的楊氏模量隨著載荷的增加而減少。FSP區(qū)域的壓頭下的總位錯(cuò)密度、幾何必需位錯(cuò)密度和統(tǒng)計(jì)存儲(chǔ)位錯(cuò)密度高于BM區(qū)域。納米壓痕加載過程中,BM和SZ初始屈服強(qiáng)度分別為0.595 GPa和0.551 GPa,應(yīng)變硬化指數(shù)為0.168和0.169。BM和SZ的宏觀抗壓屈服分別為0.340 GPa和0.406 GPa,符合Tabor’s壓痕理論。FSP AZ31超細(xì)晶鎂合金有較好的組織穩(wěn)定性。在不同的變形參數(shù)下AZ31超細(xì)晶鎂合金均表現(xiàn)出了超塑性。其中,在不同溫度下,應(yīng)變速率為3×10-3 s-1,1×10-3 s-1時(shí),材料的延伸率高于應(yīng)變速率為1×10-2 s-1和3×10-4 s-1時(shí)的延伸率;材料在400℃時(shí)的超塑性較好。在溫度為450℃,應(yīng)變速率為3×10-3 s-1時(shí),超細(xì)晶鎂合金的超塑性最好,延伸率為1090.8%。在高溫拉伸過程中,鎂合金的主要變形機(jī)制為晶界滑移,晶界滑移后晶界處產(chǎn)生孔洞,孔洞的匯集使得高溫拉伸試樣發(fā)生斷裂。
[Abstract]:AZ31 magnesium alloy is the most widely used wrought magnesium alloy. The study of plastic deformation behavior of ultrafine grained magnesium alloy is of great significance to the popularization and application of magnesium alloy. In this paper, AZ31 ultrafine grained magnesium alloy prepared by friction stir processing Stir processing has been studied as an object of study. The plastic deformation behavior of FSP AZ31 magnesium alloy was investigated by nano-indentation technique, and the plastic deformation behavior of FSP AZ31 magnesium alloy was studied at high temperature. Under different loading conditions, the curves are reproducible and the BM region fluctuates, which is related to the microstructure homogeneity of the material. The maximum indentation depth of. BM is greater than that of FSP. The maximum depth of Thermo-Mechanical Affected Zone-Advancing (TMAZ-ASG) and Thermo-Mechanical Affected Zone-Retreating (TMAZ-RS) of the base metal base Affected Zone-Retreating Side-SZ are 1244.9 nm, 1156.6 nm and 1142.8 nm, respectively. The maximum hardness of thermo-mechanical Affected Zone-Advancing is 1142.8 nm when the load is 5 mn, and the maximum depth of TMAZ-RS is 1244.9 nm, 1156.6 nm and 1142.8 nm, respectively, when the load is 5 mn, the maximum depth of thermo-mechanical Affected Zone-Retreating TMAZ-RSZ is 1244.9 nm, 1156.6 nm and 1142.8 nm respectively, and the maximum depth is 1244.9 nm, 1156.6 nm and 1142.8 nm, respectively. The hardness of TMAZ-AS side is the highest 1.435GPa. with the increase of load, the nano-hardness value of magnesium alloy decreases, showing obvious scale effect. The Young's modulus in the processing area of TMAZ-AS remains unchanged under different loads. The Young's modulus of BM decreases with the increase of load. The geometric required dislocation density and statistical storage dislocation density were higher than those in BM region. The initial yield strength of BM and SZ were 0.595 GPa and 0.551 GParespectively, and the strain hardening exponents of 0.168 and 0.169. BM and SZ were 0.168 and 0.169. BM and SZ, respectively, during the loading of nano-indentation, the initial yield strength of BM and SZ were 0.595 GPa and 0.551 GPA, respectively. It is 0.340 GPa and 0.406GPa. it accords with Tabor's indentation theory. FSP AZ31 ultrafine grained magnesium alloy has good microstructure stability. The superplasticity of AZ31 ultrafine grained magnesium alloy is shown under different deformation parameters. At different temperature, the elongation of the material is higher than that of the strain rate of 1 脳 10 -2 s ~ (-1) and 3 脳 10 ~ (-4) s ~ (-1) when the strain rate is 3 脳 10 ~ (-3) s ~ (-1), and the superplasticity of the material is better at 400 鈩，

本文編號(hào)：1566701