变面循环轧制AZ31镁合金微观组织与力学性能研究
发布时间：2019-04-25 18:44
【摘要】：镁合金是一种具有开发前景的轻质结构材料。但是传统塑性加工的镁合金存在强度较低,塑性较差和各向异性严重等问题。为了使镁合金在汽车,航天,电子等行业中得到更广泛的应用,探索新的塑性加工工艺、提高镁合金的综合力学性能显得尤为重要。本文通过变面循环轧制工艺制备AZ31镁合金。并对此工艺进行改进探索,形成降温变面循环轧制工艺和变面轧制板材工艺等塑性加工工艺。通过金相组织、透射电子显微镜和X射线衍射等观察变形后的微观组织。通过单轴拉伸和压缩等力学性能实验分析AZ31镁合金综合力学性能的变化。并且将微观组织与力学性能相结合,深入分析微观组织对AZ31镁合金力学性能的影响,得出以下结论：(1)变面循环轧制AZ31镁合金的微观组织变化明显。动态再结晶充分,晶粒尺寸细化显著,晶粒分布均匀化；位错增殖,形成许多位错胞；孪晶分数增加,且含有纳米级的孪晶；晶粒取向和织构演化循环变化,强烈的基面织构消失。偶数次轧制后大部分基面与1道次轧制面成35°夹角。(2)变面循环轧制AZ31镁合金的综合力学性能提高显著：强度明显增加,塑性不降而升,延伸率提高,拉压不对称性改善。尤其是在变面循环轧制8道次后,AZ31镁合金的单轴拉伸屈服强度达到275MPa,比初始挤压态的强度高出近50%。(3)降温变面循环轧制AZ31镁合金的强度降低,塑性明显提高。变形温度降低,动态再结晶不充分,晶粒细化受阻。且变形后,大部分基面与1道次轧制面成35°夹角,使晶粒处于软取向,强度降低。同时,由于孪晶增加,织构弥散化严重,晶粒取向丰富,塑性明显提高。(4)变面轧制AZ31镁合金板材的力学性能优异：屈服强度比初始挤压态高出60MPa,延伸率提高。且因为变面轧制后的织构不同于传统轧制的基面板织构,所以变面轧制AZ31镁合金板材具有特殊的各向异性,轧向力学性能最优。
[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 掳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.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG339;TG146.22
本文编号：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 掳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.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG339;TG146.22
【参考文献】
相关期刊论文 前1条
1 吕渠东,吕宜振,曾小勤,丁文江,卢晨;镁合金在电子器材壳体中的应用[J];材料导报;2000年06期
，本文编号：2465367
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