本文選題：ZM5鎂合金　切入點(diǎn)：晶粒細(xì)化　出處：《中北大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：Mg-Al系合金是目前應(yīng)用最為普遍的鎂合金,目前已廣泛應(yīng)用于電子、航空航天、汽車等領(lǐng)域,在未來也有更好的應(yīng)用前景。ZM5鎂合金作為Mg-Al系合金的典型代表,以其優(yōu)良的性能而受到越來越多的關(guān)注。但其結(jié)晶溫度較寬、體積收縮率大,有明顯的晶粒粗化趨勢(shì),易產(chǎn)生縮松、熱裂等缺陷,嚴(yán)重制約了鎂合金的發(fā)展。晶粒細(xì)化能顯著提高鎂合金材料的綜合力學(xué)性能和鑄造性能,大大改善鎂合金的加工性能。本文主要以ZM5鎂合金為研究主體,采用光學(xué)顯微鏡(OM)、掃描電子顯微鏡(SEM)、能譜(EDS)等手段對(duì)Mg-Al合金晶粒細(xì)化工藝及機(jī)理進(jìn)行研究,主要探討了不同的冷卻速度和不同碳質(zhì)變質(zhì)劑及不同加入量對(duì)ZM5鎂合金顯微組織和力學(xué)性能的影響,并探索其細(xì)化機(jī)理。研究不同冷卻速率(包括金屬型銅模、金屬型鋼模,含10mm厚和20mm厚冷鐵的階梯型樹脂砂型模具)對(duì)ZM5鎂合金微觀組織和力學(xué)性能的影響規(guī)律,分析計(jì)算冷卻速率與晶粒尺寸以及綜合力學(xué)性能之間定量關(guān)系式,探索其細(xì)化規(guī)律。結(jié)果表明,隨著冷卻速度的不斷增大,ZM5鎂合金的晶粒得到明顯細(xì)化,性能也變得更加優(yōu)良。在金屬型銅模鑄造條件下,其冷卻速度最快,為7.88℃/s,其晶粒尺寸最為細(xì)小,為70.31μm;在砂型階梯模中,由各區(qū)域由薄到厚依次為Ⅰ區(qū)、Ⅱ區(qū)、Ⅲ區(qū),在砂型Ⅲ區(qū)(含10mm厚的冷鐵)中,其冷卻速度最慢,為2.94℃/s,晶粒尺寸也最為粗大,為166.43μm。其晶粒尺寸由166.43μm減小到70.31μm,減小約2.5倍。其第二相的形狀由連續(xù)的網(wǎng)狀、長(zhǎng)鏈條狀、塊狀逐漸變成不連續(xù)的雪花狀、針狀、顆粒狀。ZM5鎂合金的力學(xué)性能得到顯著提高。其硬度值由54.6HB提高到66.8HB,增幅達(dá)22%;抗拉強(qiáng)度由165MPa提高到225MPa,增幅達(dá)36%;延伸率由2.2%增加到3.5%,增幅達(dá)59%;晶粒尺寸(D)、抗拉強(qiáng)度(Rm)、硬度(HB)、延伸率(A)冷卻速率的定量關(guān)系為:D=221.33v-0.333,Rm=exp(5.21932-0.07165v+0.01246v2),HB=exp(4.05024-0.03v+0.00655v2),A=exp(0.84396-0.002579v+0.00948v2)。研究不同碳質(zhì)變質(zhì)劑(包括C2Cl6、Al-5Ti-0.8C中間合金、MnCO3)及不同加入量對(duì)ZM5鎂合金組織和性能的影響規(guī)律。實(shí)驗(yàn)結(jié)果表明,變質(zhì)劑的加入,對(duì)鎂合金起到不同程度的細(xì)化作用。C2Cl6、Al-5Ti-0.8C、MnCO3三種變質(zhì)劑的最佳加入量為:1.5%、2.4%、0.5%,其平均晶粒尺寸由未變質(zhì)的188.86μm分別減少到75.87μm、90.34μm、103.75μm,抗拉強(qiáng)度較未添加的分別增加了16.2%(鑄態(tài))、39.0%(T6熱處理態(tài));5.9%(鑄態(tài))、36.6%(T6熱處理態(tài));5.4%、19.5%;伸長(zhǎng)率分別增加了25.0%(鑄態(tài))、66.7%(T6熱處理態(tài));42.8%、70.0%;17.9%、26.7%。細(xì)化效果最為明顯的是C2Cl6,其次是Al-5Ti-0.8C,然后為MnCO3。采用SEM和EDS對(duì)三種碳質(zhì)變質(zhì)劑的細(xì)化機(jī)理進(jìn)行分析討論。研究結(jié)果表明,C2Cl6的加入,在鎂合金熔體中可能生成Al4C3顆粒,其可作為α-Mg的有效形核核心,有效提高其形核率,使晶粒得以細(xì)化;添加Al-5Ti-0.8C中間合金,在鎂合金熔體中可能生成TiC和Al4C3兩種顆粒,可作為α-Mg基體的有效形核核心,進(jìn)而促進(jìn)晶粒細(xì)化;加入MnCO3,一方面是由于鎂合金熔體在反應(yīng)過程中可能生成Al4C3顆粒,可作為異質(zhì)形核的核心,另一方面,由于C、Mn元素的引進(jìn),其富集于晶界,引起成分過冷,增加其在形核過程中的過冷度,使晶粒得以細(xì)化。
[Abstract]:Mg-Al alloy is one of the most common magnesium alloy, has been widely used in electronics, aerospace, automotive and other fields, in the future also has a better application prospect of magnesium alloy.ZM5 as a typical representative of Mg-Al alloy, with its excellent performance and has attracted more and more attention. But the crystallization temperature is wide a large, volume shrinkage, grain coarsening tendency is obvious, easy to produce the shrinkage, cracking and other defects, which seriously restrict the development of magnesium alloy. The grain refinement can significantly improve the mechanical properties and casting properties of magnesium alloy materials, greatly improve the processing performance of magnesium alloy. In this paper, taking ZM5 magnesium alloy as the research the main body, using optical microscopy (OM), scanning electron microscopy (SEM), energy spectrum (EDS) were studied by means of the process and mechanism of grain refinement of Mg-Al alloy, mainly discusses the different cooling rate and different carbonaceous modificator and different The influence of adding on Microstructure and mechanical properties of ZM5 magnesium alloy, and explore its refinement mechanism. Research on different cooling rate (including metal mold, metal mold steel, with 10mm thickness and 20mm thick cold iron ladder type resin sand mould) influences on Microstructure and mechanical properties of ZM5 magnesium alloy. Calculation and analysis of the quantitative relationship between cooling rate and grain size and mechanical properties, to explore the law of refinement. The results showed that with the increasing of the cooling rate, the grain of ZM5 magnesium alloy was refined, performance is more excellent. The metal type copper casting condition, the cooling speed is 7.88 DEG C, /s most small, the grain size of 70.31 mu m; in the sand mold in each region by step, from thin to thick in area I, II, III, in the sand area III (with 10mm thick cold iron), the cooling speed of the slowest, 2.94 degrees for /s crystal The grain size of the coarse, 166.43 M. the grain size from 166.43 m reduced to 70.31 m, reduced by about 2.5 times. The second phase is shaped by continuous mesh, long chain, massive gradually become discontinuous snowflake, acicular, mechanical properties of granular.ZM5 magnesium alloy has been improved. The hardness increased from 54.6HB to 66.8HB, an increase of 22%; the tensile strength increased from 165MPa to 225MPa, an increase of 36%; the elongation rate increased from 2.2% to 3.5%, an increase of 59%; the grain size (D), tensile strength (Rm), hardness (HB), elongation (A) quantitative relationship between cooling speed rate: D=221.33v-0.333, Rm=exp (5.21932-0.07165v+0.01246v2), HB=exp (4.05024-0.03v+0.00655v2), A=exp (0.84396-0.002579v+0.00948v2). Research on different carbonaceous modificator (including C2Cl6, Al-5Ti-0.8C alloy, MnCO3) and effects of different additions on Microstructure and properties of ZM5 magnesium alloy. The experimental results 琛ㄦ槑,鍙樿川鍓傜殑鍔犲叆,瀵歸晛鍚堥噾璧峰埌涓嶅悓紼嬪害鐨勭粏鍖栦綔鐢，

本文編號(hào)：1577976