發(fā)布時(shí)間：2018-03-06 00:24

  本文選題：Mg-Al-Sn-Mn鎂合金　切入點(diǎn)：顯微組織　出處：《重慶大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：鎂合金作為最輕的商用金屬結(jié)構(gòu)材料,具有高的比強(qiáng)度、比剛度,優(yōu)良的阻尼性能等優(yōu)點(diǎn)。鎂合金在航空航天、汽車、3C等領(lǐng)域逐漸受到人們的關(guān)注,成為最具發(fā)展?jié)摿Φ慕Y(jié)構(gòu)材料之一。室溫強(qiáng)度不高、塑性差等因素制約了鎂合金的發(fā)展。Mg-Al-Sn三元系具有較低的層錯(cuò)能,正發(fā)展成為一種性能優(yōu)良的新型鎂合金。然而,目前國內(nèi)外對Mg-Al-Sn的研究還不夠系統(tǒng)和深入。在本工作中,根據(jù)Mg-Al-Sn熱力學(xué)數(shù)據(jù)構(gòu)建了三元相圖并設(shè)計(jì)了Mg-x Al-y Sn-0.3Mn(x=1,3,6,9;y=1,3,5)合金。基于金相分析、掃描電鏡、能譜、X射線衍射、電子背散射衍射、透射電子顯微分析、拉伸試驗(yàn)等手段,研究了成分對鑄態(tài)合金顯微組織與力學(xué)性能的影響、成分以及加工工藝對擠壓態(tài)合金顯微組織與力學(xué)性能的影響,探討了鑄造合金的晶粒細(xì)化機(jī)制以及擠壓態(tài)合金的再結(jié)晶機(jī)制與強(qiáng)化機(jī)制,研究了部分合金的熱壓縮流變行為,確定了其本構(gòu)方程以及熱加工參數(shù)。主要結(jié)果如下:①M(fèi)g-Al-Sn-Mn合金主要含α-Mg、Mg17Al12和Mg2Sn,以及少量的含錳化合物[Al8Mn5、Al8(Mn,Fe)5]。通過edge-to-edge模型計(jì)算表明Mg17Al12與Mg2Sn存在慣習(xí)面(220)Mg2Sn//(330)Mg17Al12(夾角1.11o)、001s Mg2Sn//22—1—zMg17Al12。在合金凝固過程中,α-Mg首先形核并長大;隨著溫度的降低,Mg2Sn經(jīng)過共晶反應(yīng)L→α-Mg+Mg2Sn形核并長大;隨著溫度的進(jìn)一步降低,Mg17Al12在Mg2Sn的慣習(xí)面上通過共晶反應(yīng)L→α-Mg+Mg17Al12+Mg2Sn形核并長大;待液相消耗完畢,凝固完成。最終,鑄造合金的晶粒隨Al含量的增加而顯著細(xì)化;Sn也有一定的細(xì)化效果,但弱于Al。鑄造合金的強(qiáng)度隨合金化元素含量的增加而增加,Sn對合金的強(qiáng)化效果弱于Al。②在未完全再結(jié)晶的擠壓態(tài)Mg-x Al-y Sn-0.3Mn(x=1、3,y=1、3、5)合金中,粗大的未再結(jié)晶區(qū)域含較強(qiáng)的(101_0)、(0001)織構(gòu),未再結(jié)晶晶粒的(0001)基面法線方向以及112—0滑移方向趨向垂直于擠壓方向;合金沿?cái)D壓方向受拉應(yīng)力時(shí),未再結(jié)晶區(qū)域a基面滑移系具有較小的施密特因子。再結(jié)晶弱化(101_0)織構(gòu),使再結(jié)晶晶粒的(0001)基面以及112—0滑移方向趨向平行于擠壓方向;合金沿?cái)D壓方向受拉應(yīng)力時(shí),再結(jié)晶晶粒a基面滑移系具有較大的施密特因子。增加合金化元素含量或提高擠壓溫度可促進(jìn)再結(jié)晶,降低合金的拉伸屈服強(qiáng)度;反之可有效提高合金的拉伸屈服強(qiáng)度。Mg-x Al-y Sn-0.3Mn(x=y=1,3)合金綜合性能較優(yōu)異(屈服強(qiáng)度200 MPa、延伸率~20%)③在完全再結(jié)晶的擠壓態(tài)Mg-x Al-y Sn-0.3Mn(x=6、9,y=1、3、5)合金中,第二相(Mg17Al12、Mg2Sn)在熱擠壓過程中動態(tài)析出,有效阻礙再結(jié)晶晶粒長大,使成分、擠壓溫度對再結(jié)晶晶粒尺寸的影響變小;固溶強(qiáng)化、第二相強(qiáng)化是合金主要的強(qiáng)化機(jī)制。增加合金化元素含量或提高擠壓溫度可有效提高合金的拉伸屈服強(qiáng)度;Mg-9Al-y Sn-0.3Mn(y=1,3,5)合金具有較高的屈服強(qiáng)度(280 MPa)。④在擠壓態(tài)Mg-Al-Sn-Mn合金中,分別研究了Al8Mn5、Mg2Sn、Mg17Al12與Mg基體的位向關(guān)系。Mg2Sn沿基面析出,兩者位向關(guān)系為:(0001)Mg//(03?3)Mg2Sn,[21?1?0]Mg//[1?22]Mg2Sn;Mg17Al12析出相同樣沿基面析出,兩者位向關(guān)系為:(0001)Mg//(22?2)Mg17Al12,[21?1?0]Mg//[122]Mg17Al12;Al8Mn5析出相與Mg基體的位向關(guān)系為:(2_1_10)Mg//(202_0) Al8Mn5, [2_42_3]Mg//[011_1]Al8Mn5。⑤通過熱模擬實(shí)驗(yàn)研究了Mg-x Al-y Sn-0.3Mn(x=y=1,3)合金的熱壓縮行為;計(jì)算了這些合金的熱變形參數(shù),確定了這些合金的本構(gòu)方程。
[Abstract]:Magnesium alloy is the lightest structural materials, has high specific strength, stiffness, damping properties of magnesium alloy automobile. Excellent in aerospace, 3C, and other fields gradually attention, become one of the most potential structural materials. The strength at room temperature is not high, poor plasticity etc. the factors restricting the development of magnesium alloy.Mg-Al-Sn three element with low stacking fault energy, is becoming a new magnesium alloy with excellent properties. However, the current domestic and foreign research on Mg-Al-Sn systems and in-depth enough. In this work, according to the Mg-Al-Sn thermal mechanical data and construct a three element phase diagram and design Mg-x Al-y Sn-0.3Mn (x=1,3,6,9; y=1,3,5) alloy. Based on metallographic analysis, scanning electron microscopy, energy spectrum, X ray diffraction, electron backscatter diffraction, transmission electron microscopy, tensile tests, the effects of composition on cast microstructure and stress state alloy Effect of mechanical properties, composition and processing technology on the microstructure and mechanical properties of extruded alloy, discusses the mechanism of grain refinement of cast alloy and extruded alloy recrystallization mechanism and strengthening mechanism, the rheological behavior of part alloy was studied to determine the hot compression, the constitutive equations and thermal processing parameters. The main results as follows: Mg-Al-Sn-Mn alloy mainly containing alpha -Mg, Mg17Al12 and Mg2Sn, and a small amount of manganese containing compounds [Al8Mn5, Al8 (Mn, Fe) 5]. calculated by edge-to-edge model showed that Mg17Al12 and Mg2Sn (220) Mg2Sn// habit plane (330) Mg17Al12, 001s Mg2Sn//22 (angle 1.11o) - 1 - zMg17Al12. in alloy solidification process first of all, alpha -Mg nucleation and growth; with the decrease of temperature, the Mg2Sn eutectic reaction after L, alpha -Mg+Mg2Sn nucleation and growth; with a further reduction of temperature, Mg17Al12 on the Mg2Sn surface through the eutectic habitus Grow up, reaction of L alpha -Mg+Mg17Al12+Mg2Sn nucleation and liquid phase; to be consumed, solidification is completed. Finally, the grain cast alloy with the increase of Al content and significant refinement; Sn also has the certain refinement effect, but weaker than Al. increased the strength of the casting alloy with alloying element content increased, the strengthening effect of Sn on the alloy is weaker than Al. in Al-y extruded Mg-x Sn-0.3Mn not fully recrystallization (x=1,3, y=1,3,5) alloys, thick non recrystallization region containing the strong (101_0), (0001) texture, no recrystallization grains (0001) and 112 in the surface normal direction perpendicular to the sliding direction trend - 0 the extrusion direction along the extrusion direction; alloy tensile stress, the Schmidt factor Nonrecrystallization region a basal slip system has smaller recrystallization. Weakening (101_0) texture, make recrystallization grains (0001) surface and 112 - 0 slip orientation parallel to the extrusion direction along the alloy; The extrusion direction tensile stress, recrystallization grain a basal slip system has greatly increased the Schmidt factor. Alloying element content or improving extrusion temperature can promote the recrystallization, reduce the alloy tensile yield strength; and can effectively improve the tensile yield strength of.Mg-x Al-y Sn-0.3Mn (x=y=1,3) with excellent properties (yield alloy the intensity of 200 MPa, ~20%) in the elongation of the extruded Mg-x Al-y Sn-0.3Mn fully recrystallized (x=6,9, y=1,3,5) alloys, the second phase (Mg17Al12, Mg2Sn) Dynamic Precipitation in hot extrusion process, effectively prevent the recrystallization, the composition, effect of extrusion temperature on recrystallization grain size becomes smaller; solid solution strengthening, second phase strengthening mechanism of the alloy. The main alloying element content increasing or improving extrusion temperature can effectively improve the tensile yield strength; Mg-9Al-y Sn-0.3Mn (y=1,3,5) alloy has High yield strength (280 MPa). The extruded Mg-Al-Sn-Mn alloy, Mg2Sn, Al8Mn5, Mg17Al12 and Mg respectively, the matrix orientation relationship of.Mg2Sn along the surface precipitation, the two orientation relationship: (0001) Mg// (03? 3) Mg2Sn, [21? 1? 0]Mg//[1? 22]Mg2Sn Mg17Al12 the same kind of precipitation; along the surface precipitation, the two orientation relationship: (0001) Mg// (22? 2) Mg17Al12, [21? 1? 0]Mg//[122]Mg17Al12; Al8Mn5 precipitates and Mg matrix orientation relationship: (2_1_10) Mg// (202_0) Al8Mn5, [2_42_3]Mg//[011_1]Al8Mn5. and Mg-x Al-y Sn-0.3Mn were studied by thermal simulation (x=y=1,3) compression behavior of the alloy heat the calculation of these alloys; hot deformation parameters, determine the constitutive equations of these alloys.

【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TG146.22

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1 佘加;Mg-Al-Sn-Mn系鎂合金顯微組織與力學(xué)性能的研究[D];重慶大學(xué);2015年

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本文編號：1572555