本文選題：壓鑄鎂合金 + 力學(xué)性能��； 參考：《吉林大學(xué)》2017年博士論文

【摘要】：鎂合金是目前汽車工業(yè)上具有廣闊發(fā)展前景的輕量化工程材料,其具有低密度、高比強(qiáng)度、切削加工性能好、鑄造性能佳、可以回收利用等優(yōu)異性能。而壓鑄鎂合金是鎂合金中使用最為廣泛的一種,目前有許多企業(yè)正在研發(fā)由壓鑄鎂合金制造的方向盤骨架、座椅骨架、儀表板骨架等零部件。然而,壓鑄鎂合金的力學(xué)性能和腐蝕性能較差,限制了此類材料的發(fā)展。因此,針對壓鑄鎂合金使用性能提高的研究,成為國內(nèi)外輕金屬領(lǐng)域研究的重點和難點。本工作主要針對Mg-Al系壓鑄AZ91鎂合金和壓鑄AM50鎂合金,采用無損探傷、拉伸、浸泡腐蝕、三維顯微組織重構(gòu)、金相觀察、掃描電鏡等多種測試和觀察手段,對合金的顯微組織及其內(nèi)部缺陷特征、合金的力學(xué)性能以及腐蝕性能展開系統(tǒng)地研究,并對其對應(yīng)關(guān)系進(jìn)行討論和模擬,從而掌握Mg-Al系壓鑄鎂合金顯微組織對力學(xué)性能和腐蝕性能影響的規(guī)律,為改善合金的性能提供一定的理論依據(jù)。具體研究成果包括:1、研究了壓鑄AZ91鎂合金的顯微缺陷對力學(xué)性能的影響規(guī)律。壓鑄AZ91鎂合金顯微組織主要由α-Mg相、β-Mg17Al12相組成,并含有一定數(shù)量的氣孔和縮松缺陷。各相以及顯微缺陷的尺寸以及分布在空間上均存在不均勻的特點:自鑄件表面至中心區(qū)域,α相尺寸逐漸增大、β相數(shù)量減少、氣孔及縮松尺寸和數(shù)量均增高。根據(jù)三維顯微重構(gòu)模型進(jìn)行統(tǒng)計,氣孔尺寸范圍為4~505μm左右,其中絕大多數(shù)氣孔尺寸為100μm左右。結(jié)合拉伸實驗和有限元模擬結(jié)果可知,氣孔的尺寸、分布、橫截面上氣孔面積百分比最大值(MPAF)等因素對合金的抗拉強(qiáng)度和延伸率有明顯不利影響。隨著材料內(nèi)部最大氣孔尺寸增大,合金的抗拉強(qiáng)度和延伸率降低;垂直于樣品受力方向分布的氣孔對力學(xué)性能的影響比平行于受力方向分布的氣孔影響嚴(yán)重;隨MPAF增大,合金的抗拉強(qiáng)度和延伸率降低:MPAF每增加1%,合金的延伸率降低大約0.37%,抗拉強(qiáng)度降低大約12.02MPa。2、研究了壓鑄AM50鎂合金的顯微組織對力學(xué)性能的影響規(guī)律。壓鑄AM50鎂合金顯微組織主要由α-Mg相、β-Mg17Al12相和少量的Al Mn相組成,并含有一定數(shù)量的顯微缺陷。相對于壓鑄AZ91鎂合金,壓鑄AM50鎂合金中顯微缺陷的數(shù)量及尺寸均較小,氣孔的尺寸普遍小于100μm,有極少量較大尺寸的氣孔,合金力學(xué)性能較好。結(jié)合拉伸試驗和有限元模擬結(jié)果,氣孔對于hpdcam50鎂合金的力學(xué)性能有不利影響,其中氣孔的尺寸和在橫截面上面積比的最大值(mpaf)是兩個主要影響因素。隨著hpdcam50鎂合金內(nèi)氣孔尺寸的增大,樣品的抗拉強(qiáng)度和延伸率均下降。同時,隨著氣孔在橫截面上面積比的最大值的數(shù)值增大,樣品的抗拉強(qiáng)度和延伸率也均近似線性下降。mpaf每升高1%,hpdcam50鎂合金的抗拉強(qiáng)度降低大約12.28mpa,而延伸率降低1.96%。冷隔、裂紋等缺陷對合金力學(xué)性能影響嚴(yán)重,會導(dǎo)致在拉伸過程中超出屈服強(qiáng)度后過早失效。3、合金凝固過程中不同的冷速會形成不同的顯微組織。不同厚度的hpdcam50鎂合金由于具有不同的顯微組織,因而其耐腐蝕性能有所差別。對于厚度從3.0mm至4.5mm的樣品而言,耐腐蝕性能先減弱再增強(qiáng),在3.5mm厚度左右其耐腐蝕性能最差。腐蝕速度與α-mg晶粒尺寸、β相分布以及孔隙存在情況有關(guān):α-mg晶粒尺寸的增大、枝晶數(shù)目的增多、β相連續(xù)性的減弱,或孔隙含量增高,均可能導(dǎo)致合金的腐蝕速度增加。此外,在利用光學(xué)顯微鏡觀察腐蝕的合金樣品表面形貌時,暗場像(darkfieldimage,dfi)相對于通常的顯微觀察中常用的明場像(brightfieldimage,bfi)具有顯著的優(yōu)勢。使用暗場像能夠較為容易的觀察到腐蝕區(qū)域的細(xì)微變化。4、改善壓鑄鎂合金的顯微組織主要有三個途徑:(1)優(yōu)化壓鑄過程工藝參數(shù);(2)采取全新壓鑄方式;(3)添加能夠改善顯微組織的合金元素。本研究中以改善合金顯微組織為目的,使用procast軟件對壓鑄am50鎂合金的三個工藝參數(shù)進(jìn)行測試和優(yōu)化,獲得的相對較好的參數(shù)搭配為:澆注溫度670℃,模具溫度200℃,壓射速度2.0m/s。5、針對在本研究中遇到的超聲波無損探傷過程中的實際性問題,設(shè)計了兩種自動超聲波探傷裝置,分別用于回轉(zhuǎn)體試樣和不規(guī)則形狀試樣的超聲波無損探傷。這兩項設(shè)計通過使用萬能夾具、多方向運(yùn)動機(jī)構(gòu)、自動噴涂設(shè)備等,主要解決了探傷過程中樣品夾持不便、探頭運(yùn)行軌跡不規(guī)律、耦合劑噴涂困難等問題,實現(xiàn)了超聲波無損探傷的自動化、三維化和高效化。6、針對金相圖像采集在獲取鑄造缺陷形貌特征中的片面性和隨機(jī)性問題,運(yùn)用三維顯微組織重構(gòu)方法,實現(xiàn)了對組織內(nèi)部缺陷的重建,達(dá)到使缺陷尺寸、形狀、分布等特征直觀、準(zhǔn)確的目標(biāo)。
[Abstract]:Magnesium alloy is a lightweight engineering material with broad development prospects in the automobile industry. It has excellent properties such as low density, high specific strength, good cutting performance, good casting performance, and can be recycled. And die-casting magnesium alloys are the most widely used in magnesium alloys. At present, many enterprises are developing die cast magnesium alloys. However, the mechanical properties and corrosion properties of the die cast magnesium alloys are poor, which limits the development of such materials. Therefore, the research on the improvement of the performance of the die casting magnesium alloys has become the key and difficult point in the field of light metal research at home and abroad. This work is mainly aimed at the Mg-Al system pressure. AZ91 magnesium alloy and die-casting AM50 magnesium alloy are made by nondestructive testing, tensile, immersion corrosion, three-dimensional microstructure reconstruction, metallographic observation, scanning electron microscopy and other testing and observation methods. The microstructure and internal defects of the alloy, the mechanical properties and corrosion properties of the alloys are systematically studied, and their corresponding relations are discussed. The influence of microstructure of Mg-Al die-casting magnesium alloy on mechanical properties and corrosion properties is mastered to provide a theoretical basis for improving the properties of the alloy. The specific research results include: 1, the influence of the micro defects on the mechanical properties of the die casting AZ91 magnesium alloy is studied. The microstructure of the die cast AZ91 magnesium alloy is mainly composed of the microstructure of the die casting alloy. The alpha -Mg phase and beta -Mg17Al12 phase consist of a certain number of stomata and shrinkage defects. The size and distribution of the phases and microdefects are uneven in space: the size of the alpha phase increases gradually from the casting surface to the central region, the number of beta phase decreases, the size and quantity of stomata and shrinkage are all increased. The size range of the stomata is about 4~505 mu m, and most of the pores are about 100 mu m. The size and distribution of the pores and the maximum percentage of the pore area on the cross section (MPAF) have obvious adverse effects on the tensile strength and elongation of the alloy. The tensile strength and elongation of the alloy increased, the tensile strength and elongation of the alloy decreased, and the influence of the air hole perpendicular to the direction of force distribution on the mechanical properties was more serious than that of the air hole parallel to the distribution of the force. The tensile strength and elongation of the alloy decreased with the increase of MPAF: the elongation of the alloy decreased by about 0.37% per increase of 1%. The tensile strength decreased by about 12.02MPa.2. The influence of microstructure on the mechanical properties of the die cast AM50 magnesium alloy was studied. The microstructure of the die cast AM50 magnesium alloy consists mainly of alpha -Mg phase, beta -Mg17Al12 phase and a small amount of Al Mn, and contains a certain number of microscopic defects. The size and size are smaller, the size of the pores is generally less than 100 m, with a very small size of the pores, and the mechanical properties of the alloy are better. In combination with the tensile test and the finite element simulation results, the porosity has a negative effect on the mechanical properties of the hpdcam50 magnesium alloy, and the size of the pores and the maximum value of the area ratio on the cross section (mpaf) are two. The tensile strength and elongation of the sample decreased with the increase of the pore size in the hpdcam50 magnesium alloy. At the same time, the tensile strength and elongation of the sample decreased approximately linearly with the increase of the maximum value of the area ratio on the cross section, and the tensile strength of the hpdcam50 magnesium alloy decreased by about 1% per liter, and the tensile strength of the hpdcam50 magnesium alloy decreased approximately. 12.28mpa, while the elongation reduction of 1.96%. cold septum, crack and other defects have a serious effect on the mechanical properties of the alloy, which will lead to premature failure of.3 after the tensile process exceeding the yield strength. The different cooling rates of the alloy during the solidification process will form different microstructure. The different thickness of the hpdcam50 magnesium alloy is resistant to the microstructure, thus it is resistant to the microstructure. Corrosion resistance is different. For samples with thickness from 3.0mm to 4.5mm, corrosion resistance is first weakened and re enhanced, and its corrosion resistance is the worst at the thickness of 3.5mm. The corrosion rate is related to alpha -mg grain size, beta phase distribution and pore existence: increasing the size of alpha -mg grain, increasing dendrite number, decreasing the continuity of beta phase, or In addition, the dark field image (darkfieldimage, DFI) has a significant advantage over common microscopic observations (brightfieldimage, BFI), when using optical microscopy to observe the surface morphology of corroded alloy samples. There are three main ways to improve the microstructure of the die cast magnesium alloy: (1) to optimize the process parameters of the die casting process; (2) to adopt a new die-casting method and (3) to add alloy elements that can improve the microstructure of the alloy. The purpose of this study is to improve the microstructure of the alloy and use the software of ProCAST to die casting AM50 magnesium alloy. Three process parameters are tested and optimized, and the relatively good parameters are as follows: pouring temperature 670, die temperature 200, and injection speed 2.0m/s.5. Aiming at the practical problems in the process of ultrasonic nondestructive testing encountered in this study, two kinds of automatic hyper acoustic detection devices are designed to be used in rotary body samples and unconventional. The two designs, through the use of universal jig, multi direction moving mechanism and automatic spraying equipment, mainly solve the problems of the inconvenience of sample holding, the irregular track of the probe and the difficulty of the coupling agent spraying, which have realized the automation of ultrasonic nondestructive testing, three-dimensional and efficient.6, In view of the one-sided and randomicity of metallographic image acquisition in the feature of casting defects, three-dimensional microstructure reconstruction is used to reconstruct the internal defects of the tissue, which can make the defect size, shape, distribution and so on intuitionistic and accurate.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：TG249.2;TG146.22

【相似文獻(xiàn)】

相關(guān)期刊論文 前10條

1 鄧鋼 ,張京萍;壓鑄鎂合金的市場及應(yīng)用[J];特種鑄造及有色合金;2001年06期

2 王祝堂;壓鑄鎂合金在汽車中的應(yīng)用[J];輕金屬;1997年07期

3 呂宜振,翟春泉,王渠東,曾小勤,朱燕萍;壓鑄鎂合金的應(yīng)用現(xiàn)狀及發(fā)展趨勢[J];鑄造;1998年12期

4 張詩昌,魏伯康,林漢同;耐高溫壓鑄鎂合金的發(fā)展及研究現(xiàn)狀[J];中國稀土學(xué)報;2003年S1期

5 曾正南;彭小仙;劉楚明;;壓鑄鎂合金及其應(yīng)用[J];金屬材料與冶金工程;2007年02期

6 廖慧敏;龍思遠(yuǎn);石光華;;壓鑄鎂合金方向盤裂紋的分析及防止[J];鑄造;2008年09期

7 常青梅;龍思遠(yuǎn);曹韓學(xué);劉偉召;朱茜;;壓鑄鎂合金輪狀產(chǎn)品的結(jié)構(gòu)優(yōu)化設(shè)計[J];特種鑄造及有色合金;2010年03期

8 游國強(qiáng);杜娟;譚霞;王向杰;;壓鑄鎂合金焊接氣孔問題研究現(xiàn)狀及發(fā)展[J];功能材料;2013年04期

9 喻忠毅;壓鑄鎂合金和性能[J];現(xiàn)代鑄造;1981年04期

10 東華;高溫鎂合金AE42X1[J];材料工程;1992年02期

相關(guān)會議論文 前6條

1 段友麗;楚文海;趙建華;;改進(jìn)層次分析法和模糊綜合評判實現(xiàn)壓鑄鎂合金選材[A];2008重慶市鑄造年會論文集[C];2008年

2 曹建勇;;鎂壓鑄產(chǎn)品發(fā)展現(xiàn)狀及未來展望[A];2011重慶市鑄造年會論文集[C];2011年

3 劉娟;龍思遠(yuǎn);王進(jìn)峰;;壓鑄摩托車輪轂服役狀態(tài)的數(shù)值模擬[A];2013(第23屆)重慶市鑄造年會論文集[C];2013年

4 張永發(fā);曾德友;羅章瑜;;壓鑄鎂合金摩托車曲軸箱體的開發(fā)[A];海峽兩岸第二屆工程材料研討會論文集[C];2004年

5 宋東福;趙雅情;戚文軍;梁濤;農(nóng)登;;壓鑄鎂合金植酸轉(zhuǎn)化處理中添加劑的研究[A];2013廣東材料發(fā)展論壇——戰(zhàn)略性新興產(chǎn)業(yè)發(fā)展與新材料科技創(chuàng)新研討會論文摘要集[C];2013年

6 郝婷婷;曹韓學(xué);趙東林;;模鍛對AZ91壓鑄鎂合金組織和力學(xué)性能的影響[A];2012(第22屆)重慶市鑄造年會論文集[C];2012年

相關(guān)重要報紙文章 前1條

1 楊欣;我國急需制定鎂行業(yè)新標(biāo)準(zhǔn)[N];國際經(jīng)貿(mào)消息;2001年

相關(guān)博士學(xué)位論文 前2條

1 姜巍;Mg-Al系壓鑄鎂合金顯微組織對力學(xué)性能和腐蝕性能影響的研究[D];吉林大學(xué);2017年

2 王峰;壓鑄鎂合金組織與力學(xué)性能及復(fù)雜鑄件成形研究[D];沈陽工業(yè)大學(xué);2010年

相關(guān)碩士學(xué)位論文 前4條

1 趙旭;釔元素對壓鑄鎂合金熔化焊接氣孔的影響[D];重慶大學(xué);2015年

2 杜娟;壓鑄鎂合金熔化焊接氣孔的形成機(jī)理及消除措施[D];重慶大學(xué);2014年

3 郭成偉;壓鑄鎂合金AM50的組織和力學(xué)性能[D];吉林大學(xué);2015年

4 霍成鵬;壓鑄鎂合金汽車轉(zhuǎn)向管柱支架CAE[D];沈陽工業(yè)大學(xué);2012年

，

本文編號：1925665