本文選題：超高強(qiáng)鋁合金 + 變形特性��； 參考：《中北大學(xué)》2016年博士論文

【摘要】：超高強(qiáng)鋁合金具有高的比強(qiáng)度和硬度、耐久且經(jīng)濟(jì)、易于加工、較好的耐腐蝕性能和較高的韌性等優(yōu)點(diǎn),已成為航空和航天、兵器、交通運(yùn)輸?shù)刃袠I(yè)首選結(jié)構(gòu)材料之一。以自主研發(fā)的超高強(qiáng)鋁合金(Al-12Zn-2.4Mg-1.2Cu-0.3Zr-0.05 Ni)為研究對(duì)象,通過(guò)熱模擬試驗(yàn)展開(kāi)合金的熱變形特性研究;在開(kāi)展不同工藝參數(shù)對(duì)合金力學(xué)性能影響的基礎(chǔ)上,以某型號(hào)用心部雙凸盤(pán)形零件作為應(yīng)用目標(biāo)構(gòu)件,針對(duì)其高服役性能和性能均一性要求,結(jié)合合金自身應(yīng)力敏感性特點(diǎn),提出了狀態(tài)參量(?'和?)和過(guò)程參量(W??)作為均勻性評(píng)價(jià)指標(biāo),開(kāi)展成形方案設(shè)計(jì)及成形均勻性研究;采用灰色關(guān)聯(lián)理論與正交試驗(yàn)法相結(jié)合的優(yōu)化設(shè)計(jì)方法,借助于數(shù)值仿真技術(shù),開(kāi)展了目標(biāo)構(gòu)件均勻成形工藝參數(shù)優(yōu)化設(shè)計(jì)研究;最后,進(jìn)行了成形試驗(yàn)和構(gòu)件性能均一性研究。通過(guò)熱模擬試驗(yàn),開(kāi)展了合金熱變形特性研究;通過(guò)構(gòu)建熱加工圖,獲得了不同真應(yīng)變下的最佳變形工藝參數(shù)窗口;在經(jīng)典Arrhenius模型的基礎(chǔ)上,采用應(yīng)變補(bǔ)償和應(yīng)變速率敏感指數(shù)修正相結(jié)合的方法,構(gòu)建了綜合考慮應(yīng)變補(bǔ)償和應(yīng)變速率指數(shù)修正的模型。與經(jīng)典模型相比,預(yù)測(cè)精度提高了24.88%�；诹髯兦�和加工硬化率理論,開(kāi)展了合金動(dòng)態(tài)再結(jié)晶臨界條件研究,構(gòu)建了合金發(fā)生動(dòng)態(tài)再結(jié)晶臨界應(yīng)力和應(yīng)變條件模型。借助于金相檢測(cè)技術(shù),開(kāi)展了不同變形條件下的動(dòng)態(tài)再結(jié)晶微觀組織觀察與表征研究,結(jié)果表明:合金的再結(jié)晶晶粒平均尺寸隨溫度的升高、應(yīng)變速率的降低而增大;隨溫度的降低、應(yīng)變速率的增加而減小。在此基礎(chǔ)上,借助于定量金相分析技術(shù)和形態(tài)學(xué)圖像處理技術(shù),建立了合金的微觀組織模型,為后續(xù)數(shù)值仿真研究提供材料模型。通過(guò)擠壓比試驗(yàn),開(kāi)展了不同工藝參數(shù)下合金力學(xué)性能響應(yīng)研究,結(jié)果表明:變形溫度和擠壓比對(duì)合金力學(xué)性能具有較顯著的影響。與初始擠壓棒材室溫力學(xué)性能(抗拉強(qiáng)度700-720MPa)相比,經(jīng)二次變形后的抗拉強(qiáng)度提高了7.9%-15.6%。針對(duì)目標(biāo)構(gòu)件高服役性能及均一性要求,結(jié)合合金自身應(yīng)力敏感性特點(diǎn),從微觀結(jié)構(gòu)和能量狀態(tài)角度,提出了狀態(tài)參量(等效應(yīng)變面密度均勻因子,?)、(等效應(yīng)力面密度均勻因子,?')和過(guò)程參量(等效耗散功增量面密度均勻因子,?W?)作為成形均勻性評(píng)價(jià)指標(biāo)。并依據(jù)狀態(tài)參量,進(jìn)行了目標(biāo)構(gòu)件成形方案設(shè)計(jì),制定出多道次等溫成形方案。首次采用了灰色關(guān)聯(lián)度與正交試驗(yàn)法相結(jié)合的工藝參數(shù)優(yōu)化設(shè)計(jì)方法,通過(guò)連續(xù)工序下多個(gè)變形參數(shù)、應(yīng)力和應(yīng)變狀態(tài)結(jié)果以及能量分布狀態(tài)結(jié)果的灰色關(guān)聯(lián)度分析,實(shí)現(xiàn)了多評(píng)價(jià)指標(biāo)的關(guān)聯(lián)集成,解決了正交試驗(yàn)法無(wú)法開(kāi)展多評(píng)價(jià)指標(biāo)下成形工藝參數(shù)優(yōu)化設(shè)計(jì)難題。在此基礎(chǔ)上,獲得多道次等溫成形工藝參數(shù)組合和連續(xù)工序下不同因素對(duì)成形均勻性影響的顯著關(guān)系。最后,進(jìn)行了目標(biāo)構(gòu)件的成形試驗(yàn)和微觀組織與性能測(cè)試表征研究。結(jié)果表明:所制定的多道次等溫成形(case2)工藝方案合理可行。case2方案成形構(gòu)件的室溫抗拉強(qiáng)度均值大于730MPa,伸長(zhǎng)率均值大于5%;較單道次成形(case1)方案分別提高了5.3%和2.3%。case2方案成形構(gòu)件的力學(xué)性能在要求取樣的方向上無(wú)顯著差異(P-value=0.168806),有效保障了成形構(gòu)件力學(xué)性能一致性;且微觀組織中再結(jié)晶體積分?jǐn)?shù)更高,平均晶粒尺寸更加細(xì)小,有效保障了成形構(gòu)件微觀組織的均勻性。case1方案成形構(gòu)件的抗拉強(qiáng)度在要求取樣的方向存在顯著差異(P-value=0.780749)。采用case2方案和優(yōu)化設(shè)計(jì)后的工藝參數(shù)制備出了力學(xué)性能一致性較好的構(gòu)件,為該合金在目標(biāo)構(gòu)件均勻成形及工程化應(yīng)用奠定了基礎(chǔ)。
[Abstract]:Ultra high strength aluminum alloy has the advantages of high specific strength and hardness, durable and economical, easy to process, good corrosion resistance and high toughness. It has become one of the preferred structural materials in aviation and aerospace, weapons, transportation and other industries. The research object is Al-12Zn-2.4Mg-1.2Cu-0.3Zr-0.05 Ni, which is developed independently. On the basis of the influence of different technological parameters on the mechanical properties of the alloy, the double convex disc parts of a certain type of heart were used as the target component, and the state parameters (? ') were put forward on the basis of the characteristics of the high service performance and uniformity of the alloy and the stress sensitivity characteristics of the alloy. And?) and process parameters (W?) as the index of uniformity evaluation, the design of forming scheme and the study of forming uniformity are carried out. The optimization design method which combines the grey relation theory with the orthogonal test method and the numerical simulation technology is used to carry out the optimization design of the uniform forming process parameters of the target component. Finally, the forming test and the forming test are carried out. The thermal deformation characteristics of the alloy were studied by the thermal simulation test. Through the construction of the thermal processing diagram, the optimum parameters window of the deformation process under different true strain was obtained. On the basis of the classic Arrhenius model, the combination of strain compensation and strain rate sensitivity index correction was used to construct a comprehensive test. In comparison with the classical model, the prediction accuracy of the model is improved by 24.88%. based on the rheological curve and the theory of machining hardening rate. The critical conditions for dynamic recrystallization of the alloy are studied, and the critical stress and strain condition model of the alloy's dynamic recrystallization is constructed. The microstructure observation and characterization of dynamic recrystallization under different deformation conditions show that the average size of recrystallized grain increases with the increase of temperature and strain rate, and decreases with the increase of temperature and strain rate. On this basis, the quantitative metallographic analysis and morphological image processing are used. The microstructure model of the alloy was established, and the material model was provided for the subsequent numerical simulation. The mechanical properties of the alloy under the different process parameters were studied by the extrusion ratio test. The results showed that the deformation temperature and extrusion ratio had a significant influence on the mechanical properties of the alloy. Compared with the tensile strength 700-720MPa, the tensile strength after two times of deformation increases the high service performance and homogeneity of the target member by 7.9%-15.6%.. According to the characteristics of the stress sensitivity of the alloy, the state parameters (equivalent strain surface density uniformity factor,?) are proposed from the micro structure and energy state. The process parameters (the equivalent of the equivalent dissipative energy increment surface density factor, W?) are used as the evaluation index of the forming uniformity. The forming scheme of the target component is designed according to the state parameters, and the multi-channel isothermal forming scheme is formulated. The method of optimizing the process parameters combining the grey correlation with the orthogonal test method is first adopted. The grey correlation analysis of multiple deformation parameters, stress and strain state results and energy distribution state results in the continuous process has realized the association integration of multi evaluation index, and solved the problem of optimization design for forming process parameters under the multi evaluation index of orthogonal test. On this basis, the multi pass isothermal forming process was obtained. The significant relationship between the parameters combination and the influence of different factors on the forming uniformity in the continuous process. Finally, the forming test of the target component and the characterization of the microstructure and performance test are carried out. The results show that the multi pass isothermal forming (case2) process is reasonable and feasible, and the mean of the tensile strength of the forming component at room temperature is larger than that of the.Case2 scheme. In 730MPa, the average elongation is greater than 5%, and the mechanical properties of the 5.3% and 2.3%.case2 schemes have no significant difference (P-value=0.168806) in the direction of sampling, which can effectively guarantee the mechanical properties of the forming components, and the volume fraction of the recrystallization in the microstructures is higher, and the average grain size is higher. The size is more small and the microstructure uniformity of the forming component is effectively guaranteed. The tensile strength of the.Case1 forming component is significantly different in the direction of the required sampling (P-value=0.780749). The components with good mechanical properties are prepared by using the case2 scheme and the optimized design parameters, which is the alloy in the target component. The foundation of the homogenization and engineering application is laid.

【學(xué)位授予單位】：中北大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG146.21
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本文編號(hào)：1894325