【摘要】：鎂合金被譽(yù)為21世紀(jì)可持續(xù)發(fā)展的“綠色材料”,也是目前最輕的金屬結(jié)構(gòu)材料,具有很高的比強(qiáng)度,主要應(yīng)用于醫(yī)學(xué)、3C電子產(chǎn)品、汽車(chē)、航空航天等各個(gè)領(lǐng)域,已然成為世界各國(guó)關(guān)注和研究的焦點(diǎn)。由于鎂合金具有密排六方結(jié)構(gòu)的特點(diǎn),在室溫變形條件下獨(dú)立的滑移系較少,因此室溫下塑性差,變形加工困難,需要采用大塑性變形復(fù)合工藝才能有效的細(xì)化鎂合金晶粒,以提高鎂合金的塑性,從而改善其加工性能。以促進(jìn)變形鎂合金產(chǎn)品在各個(gè)領(lǐng)域的廣泛應(yīng)用。由于傳統(tǒng)的鎂合金擠壓棒材的變形能力和強(qiáng)韌性差,采用等通道轉(zhuǎn)角擠壓大塑性變形技術(shù)(ECAP),即由兩個(gè)相交的等徑通道組成的模具并通過(guò)純剪切方式實(shí)現(xiàn)塊體金屬材料大塑性變形的成形工藝,它能夠有效的制備超細(xì)晶結(jié)構(gòu)材料,但是,需要多道次等通道轉(zhuǎn)角擠壓成形才能獲得組織均勻的高性能材料,并且在多道次擠壓過(guò)程中還容易出現(xiàn)開(kāi)裂現(xiàn)象,因此,這種大塑性變形工藝難以進(jìn)行工業(yè)化推廣。本文基于等通道轉(zhuǎn)角擠壓工藝的缺陷,提出并設(shè)計(jì)了等通道轉(zhuǎn)角擠壓與正擠壓相復(fù)合的累積變形工藝(以下簡(jiǎn)稱(chēng)ECAP-FE),即在等通道轉(zhuǎn)角擠壓型腔后直接連接一個(gè)具有一定擠壓比的正擠壓芯模,由此形成一個(gè)集多種變形工藝于一體的連續(xù)擠壓型腔,從而實(shí)現(xiàn)對(duì)材料的累積塑性變形。由此找到一種提高鎂合金塑性的新途徑。本文首先采用二次開(kāi)發(fā)技術(shù)在MSC.Marc軟件中建立了AZ31鎂合金的材料模型,然后構(gòu)建了AZ31鎂合金微觀組織預(yù)測(cè)系統(tǒng)的程序開(kāi)發(fā)流程圖,并利用FORTRAN語(yǔ)言對(duì)微觀組織模型進(jìn)行編程,成功的預(yù)測(cè)了擠壓過(guò)程中AZ31鎂合金的晶粒尺寸和動(dòng)態(tài)再結(jié)晶體積分?jǐn)?shù)的變化過(guò)程。將構(gòu)建成功的AZ31鎂合金的ECAP-FE擠壓過(guò)程有限元分析模型進(jìn)行數(shù)值模擬。最后對(duì)AZ31鎂合金在ECAP-FE擠壓模擬過(guò)程中的擠壓力、等效應(yīng)力場(chǎng)、等效應(yīng)變場(chǎng)、等效應(yīng)變速率進(jìn)行有限元分析。模擬結(jié)果表明:與單一的ECAP擠壓工藝相比,ECAP-FE復(fù)合擠壓變形工藝能有效的提高材料的變形量,使材料產(chǎn)生累積變形,細(xì)化晶粒;并且,ECAP-FE復(fù)合擠壓變形工藝所獲得的平均等效應(yīng)變提高了約2倍,等效不均勻系數(shù)有很大幅度的下降,且等效應(yīng)變呈軸對(duì)稱(chēng)分布,因此ECAP-FE能實(shí)現(xiàn)較高的累積塑性變形;而且,在ECAP-FE復(fù)合擠壓工藝中,正擠壓的模面能夠?yàn)镋CAP擠壓過(guò)程提供有效背壓,減小剪切帶面積,使之更接近理想的簡(jiǎn)單切變;使得經(jīng)ECAP-FE擠壓后的最大等效應(yīng)變速率為0.9916,最大等效應(yīng)變速率顯著提高。由此表明ECAP-FE復(fù)合累積塑性變形工藝可獲取更加細(xì)小、均勻的晶粒組織。此結(jié)果為ECAP-FE復(fù)合擠壓工藝的進(jìn)一步深入研究提供了理論依據(jù)。
[Abstract]:Magnesium alloys are praised as "green materials" for sustainable development in the 21st century. They are also the lightest metal structural materials at present. They have high specific strength and are mainly used in medicine, 3C electronic products, automobiles, aerospace and other fields. Has become the focus of attention and research around the world. Because magnesium alloy has the characteristic of dense hexagonal structure and there are few independent slip systems under room temperature deformation, it is difficult to deform and deform at room temperature, so it is necessary to use large plastic deformation composite process to refine magnesium alloy grain effectively. In order to improve the plasticity of magnesium alloys and improve their processing properties. In order to promote the wide application of wrought magnesium alloy products in various fields. Due to the poor deformation ability and strength and toughness of the traditional magnesium alloy extruded bar, (ECAP), is used to extrude large plastic deformation technology at equal channel angle. That is, the mould composed of two intersecting equal channels and the forming process of large plastic deformation of bulk metal material by pure shear, it can effectively prepare ultrafine crystal structure material, but, High performance materials with uniform microstructure can be obtained by multi-pass secondary channel angular extrusion forming, and cracking is easy to occur in multi-pass extrusion process. Therefore, this kind of large plastic deformation process is difficult to be popularized in industry. Based on the defects of the equal channel angular extrusion process, the cumulative deformation process of equal channel angular extrusion and forward extrusion (hereinafter referred to as ECAP-FE) is proposed and designed in this paper. That is, a positive extrusion core die with a certain extrusion ratio is connected directly behind the equal channel angular extrusion cavity, and a continuous extrusion cavity with multiple deformation processes is formed, thus the cumulative plastic deformation of the material is realized. Therefore, a new way to improve the plasticity of magnesium alloy is found. In this paper, the material model of AZ31 magnesium alloy is established by using secondary development technology in MSC.Marc software, then the program development flow chart of AZ31 magnesium alloy microstructure prediction system is constructed, and the microstructure model of AZ31 magnesium alloy is programmed by FORTRAN language. The change of grain size and dynamic recrystallization integral number of AZ31 magnesium alloy during extrusion was successfully predicted. The finite element analysis model of ECAP-FE extrusion process of AZ31 magnesium alloy was numerically simulated. Finally, the extrusion force field, equivalent strain rate and equivalent strain field of AZ31 magnesium alloy during ECAP-FE extrusion simulation are analyzed by finite element method. The simulation results show that compared with the single ECAP extrusion process, the ECAP-FE composite extrusion process can effectively increase the amount of deformation of the material, make the material produce cumulative deformation and refine the grain. Moreover, the average equivalent strain obtained by ECAP-FE composite extrusion process has increased by about 2 times, and the equivalent inhomogeneity coefficient has been greatly reduced, and the equivalent strain has been distributed symmetrically, so ECAP-FE can achieve higher cumulative plastic deformation. Moreover, in the process of ECAP-FE composite extrusion, the die face of forward extrusion can provide effective back pressure for ECAP extrusion process, reduce the area of shear band, and make it closer to the ideal simple shear. The maximum equivalent strain rate after ECAP-FE extrusion is 0.9916, and the maximum equivalent strain rate increases significantly. It is shown that ECAP-FE composite cumulative plastic deformation process can obtain more fine and uniform grain structure. The results provide a theoretical basis for the further study of ECAP-FE composite extrusion process.
【學(xué)位授予單位】：哈爾濱理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG379

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 任朋立;;鎂合金開(kāi)發(fā)應(yīng)用現(xiàn)狀及其發(fā)展策略[J];新材料產(chǎn)業(yè);2014年04期

2 吳遠(yuǎn)志;嚴(yán)紅革;陳吉華;朱素琴;薄紅偉;王林偉;;AZ31鎂合金高應(yīng)變速率多向鍛造組織演變及力學(xué)性能[J];中國(guó)有色金屬學(xué)報(bào);2012年11期

3 陳貴清;傅高升;程超增;顏文煅;鄒則昌;林紹義;;應(yīng)變速率對(duì)3003鋁合金熱變形動(dòng)態(tài)再結(jié)晶組織的影響[J];材料熱處理學(xué)報(bào);2012年10期

4 李峰;林俊峰;張?chǎng)锡?潘強(qiáng)榮;;連續(xù)變截面直接擠壓成形技術(shù)研究[J];材料科學(xué)與工藝;2012年05期

5 任國(guó)成;趙國(guó)群;徐淑波;王桂青;;AZ31鎂合金等通道轉(zhuǎn)角擠壓變形均勻性有限元分析[J];中國(guó)有色金屬學(xué)報(bào);2011年04期

6 何運(yùn)斌;潘清林;覃銀江;劉曉艷;李文斌;Yu-lung CHIU;John J J CHEN;;等通道角擠壓制備細(xì)晶ZK60鎂合金的組織與力學(xué)性能[J];中國(guó)有色金屬學(xué)報(bào);2010年12期

7 王偉之;程先華;;A Finite Element Simulation of NiTi Alloy during Equal Channel Angular Extrusion[J];Journal of Wuhan University of Technology(Materials Science Edition);2010年05期

8 劉曉峰;張敏剛;孫述利;孫鋼;柴躍生;;數(shù)值模擬內(nèi)圓角半徑對(duì)AZ31鎂合金等徑角擠壓過(guò)程的影響[J];特種鑄造及有色合金;2010年06期

9 張丁非;胡紅軍;潘復(fù)生;楊明波;張鈞萍;;Numerical and physical simulation of new SPD method combining extrusion and equal channel angular pressing for AZ31 magnesium alloy[J];Transactions of Nonferrous Metals Society of China;2010年03期

10 王麗娟;;熱鍛成形過(guò)程微觀組織模擬的研究概況[J];機(jī)電設(shè)備;2010年02期

相關(guān)博士學(xué)位論文 前1條

1 康鋒;背壓對(duì)鎂合金等徑角變形的作用[D];南京理工大學(xué);2010年

相關(guān)碩士學(xué)位論文 前3條

1 張文慈;鈦合金棒線材連軋孔型系統(tǒng)研究[D];太原科技大學(xué);2011年

2 葉永南;AZ31鎂合金往復(fù)擠壓成形熱力耦合模擬研究[D];西安理工大學(xué);2007年

3 陳戟銘;薄壁管數(shù)控彎曲成形壁厚變薄的數(shù)值分析[D];西北工業(yè)大學(xué);2003年

，

本文編號(hào)：2415092