變面循環(huán)軋制AZ31鎂合金微觀組織與力學(xué)性能研究
發(fā)布時(shí)間：2019-04-25 18:44
【摘要】：鎂合金是一種具有開發(fā)前景的輕質(zhì)結(jié)構(gòu)材料。但是傳統(tǒng)塑性加工的鎂合金存在強(qiáng)度較低,塑性較差和各向異性嚴(yán)重等問題。為了使鎂合金在汽車,航天,電子等行業(yè)中得到更廣泛的應(yīng)用,探索新的塑性加工工藝、提高鎂合金的綜合力學(xué)性能顯得尤為重要。本文通過變面循環(huán)軋制工藝制備AZ31鎂合金。并對此工藝進(jìn)行改進(jìn)探索,形成降溫變面循環(huán)軋制工藝和變面軋制板材工藝等塑性加工工藝。通過金相組織、透射電子顯微鏡和X射線衍射等觀察變形后的微觀組織。通過單軸拉伸和壓縮等力學(xué)性能實(shí)驗(yàn)分析AZ31鎂合金綜合力學(xué)性能的變化。并且將微觀組織與力學(xué)性能相結(jié)合,深入分析微觀組織對AZ31鎂合金力學(xué)性能的影響,得出以下結(jié)論：(1)變面循環(huán)軋制AZ31鎂合金的微觀組織變化明顯。動態(tài)再結(jié)晶充分,晶粒尺寸細(xì)化顯著,晶粒分布均勻化；位錯(cuò)增殖,形成許多位錯(cuò)胞；孿晶分?jǐn)?shù)增加,且含有納米級的孿晶；晶粒取向和織構(gòu)演化循環(huán)變化,強(qiáng)烈的基面織構(gòu)消失。偶數(shù)次軋制后大部分基面與1道次軋制面成35°夾角。(2)變面循環(huán)軋制AZ31鎂合金的綜合力學(xué)性能提高顯著：強(qiáng)度明顯增加,塑性不降而升,延伸率提高,拉壓不對稱性改善。尤其是在變面循環(huán)軋制8道次后,AZ31鎂合金的單軸拉伸屈服強(qiáng)度達(dá)到275MPa,比初始擠壓態(tài)的強(qiáng)度高出近50%。(3)降溫變面循環(huán)軋制AZ31鎂合金的強(qiáng)度降低,塑性明顯提高。變形溫度降低,動態(tài)再結(jié)晶不充分,晶粒細(xì)化受阻。且變形后,大部分基面與1道次軋制面成35°夾角,使晶粒處于軟取向,強(qiáng)度降低。同時(shí),由于孿晶增加,織構(gòu)彌散化嚴(yán)重,晶粒取向豐富,塑性明顯提高。(4)變面軋制AZ31鎂合金板材的力學(xué)性能優(yōu)異：屈服強(qiáng)度比初始擠壓態(tài)高出60MPa,延伸率提高。且因?yàn)樽兠孳堉坪蟮目棙?gòu)不同于傳統(tǒng)軋制的基面板織構(gòu),所以變面軋制AZ31鎂合金板材具有特殊的各向異性,軋向力學(xué)性能最優(yōu)。
[Abstract]:Magnesium alloy is a kind of lightweight structural material with development prospect. However, there are some problems, such as low strength, poor plasticity and serious anisotropy, in the traditional plastic-machined magnesium alloys. In order to make magnesium alloy more widely used in automotive, aerospace, electronic and other industries, it is very important to explore new plastic processing technology and improve the comprehensive mechanical properties of magnesium alloy. In this paper, AZ31 magnesium alloy was prepared by surface-changing cyclic rolling process. At the same time, the modification of this process was carried out to form plastic processing technology, such as cyclic rolling process with low temperature and variable face rolling and plate rolling with variable face. The microstructure after deformation was observed by metallography, transmission electron microscopy and X-ray diffraction. The changes of comprehensive mechanical properties of AZ31 magnesium alloy were analyzed by uniaxial tensile and compression tests. With the combination of microstructure and mechanical properties, the influence of microstructure on mechanical properties of AZ31 magnesium alloy is deeply analyzed. The following conclusions are drawn: (1) the microstructure change of AZ31 magnesium alloy during cyclic rolling with variable plane is obvious. The dynamic recrystallization is sufficient, the grain size is refined obviously, the grain distribution is homogeneous, the dislocation proliferates, many dislocation cells are formed, the twin fraction increases, and there are nano-sized twins. The grain orientation and texture evolution change circularly, and the strong base texture disappears. (2) the comprehensive mechanical properties of AZ31 magnesium alloy during cyclic rolling with variable surface are significantly improved: the strength increases obviously, the plasticity does not decrease, the elongation increases, and the tension and compression asymmetries are improved. Especially, the uniaxial tensile yield strength of AZ31 magnesium alloy reached 275 MPA after 8 passes of cyclic rolling, which was nearly 50% higher than that of the initial extrusion state. (3) the strength of AZ31 magnesium alloy was decreased and the plasticity of the alloy was improved obviously. The deformation temperature decreased, the dynamic recrystallization was not sufficient, and the grain refinement was blocked. After deformation, most of the base surfaces have a 35 擄angle with the 1 pass rolling surface, which makes the grains in soft orientation and decreases the strength. At the same time, due to the increase of twinning, the texture dispersion is serious, the grain orientation is rich, and the plasticity is obviously improved. (4) the mechanical properties of AZ31 magnesium alloy sheet rolled with variable plane are excellent: the yield strength is 60 MPA higher than that of the initial extrusion state, and the elongation is increased. Moreover, because the texture after variable-face rolling is different from the traditional rolled base-plate texture, the AZ31 magnesium alloy sheet rolled with variable-face has special anisotropy and the best rolling mechanical properties.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG339;TG146.22
本文編號：2465367
[Abstract]:Magnesium alloy is a kind of lightweight structural material with development prospect. However, there are some problems, such as low strength, poor plasticity and serious anisotropy, in the traditional plastic-machined magnesium alloys. In order to make magnesium alloy more widely used in automotive, aerospace, electronic and other industries, it is very important to explore new plastic processing technology and improve the comprehensive mechanical properties of magnesium alloy. In this paper, AZ31 magnesium alloy was prepared by surface-changing cyclic rolling process. At the same time, the modification of this process was carried out to form plastic processing technology, such as cyclic rolling process with low temperature and variable face rolling and plate rolling with variable face. The microstructure after deformation was observed by metallography, transmission electron microscopy and X-ray diffraction. The changes of comprehensive mechanical properties of AZ31 magnesium alloy were analyzed by uniaxial tensile and compression tests. With the combination of microstructure and mechanical properties, the influence of microstructure on mechanical properties of AZ31 magnesium alloy is deeply analyzed. The following conclusions are drawn: (1) the microstructure change of AZ31 magnesium alloy during cyclic rolling with variable plane is obvious. The dynamic recrystallization is sufficient, the grain size is refined obviously, the grain distribution is homogeneous, the dislocation proliferates, many dislocation cells are formed, the twin fraction increases, and there are nano-sized twins. The grain orientation and texture evolution change circularly, and the strong base texture disappears. (2) the comprehensive mechanical properties of AZ31 magnesium alloy during cyclic rolling with variable surface are significantly improved: the strength increases obviously, the plasticity does not decrease, the elongation increases, and the tension and compression asymmetries are improved. Especially, the uniaxial tensile yield strength of AZ31 magnesium alloy reached 275 MPA after 8 passes of cyclic rolling, which was nearly 50% higher than that of the initial extrusion state. (3) the strength of AZ31 magnesium alloy was decreased and the plasticity of the alloy was improved obviously. The deformation temperature decreased, the dynamic recrystallization was not sufficient, and the grain refinement was blocked. After deformation, most of the base surfaces have a 35 擄angle with the 1 pass rolling surface, which makes the grains in soft orientation and decreases the strength. At the same time, due to the increase of twinning, the texture dispersion is serious, the grain orientation is rich, and the plasticity is obviously improved. (4) the mechanical properties of AZ31 magnesium alloy sheet rolled with variable plane are excellent: the yield strength is 60 MPA higher than that of the initial extrusion state, and the elongation is increased. Moreover, because the texture after variable-face rolling is different from the traditional rolled base-plate texture, the AZ31 magnesium alloy sheet rolled with variable-face has special anisotropy and the best rolling mechanical properties.
【學(xué)位授予單位】：南京理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG339;TG146.22
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 呂渠東,呂宜振,曾小勤,丁文江,盧晨;鎂合金在電子器材殼體中的應(yīng)用[J];材料導(dǎo)報(bào);2000年06期
，本文編號：2465367
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