基于元胞自动机AZ31镁合金固溶处理研究
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摘要
镁合金具有导热导电性好、电磁屏蔽性能优越、与环境相容性良好等诸多优点。但是镁合金在室温下塑性较差,导致其在轧制过程中易出现裂纹从而影响其质量。为了有效提高其可塑性,在加工前往往需要对其进行固溶处理。基于此,通过金相实验,得到AZ31镁合金管材原始晶粒组织,基于晶粒长大的热力学机制、曲率驱动机制和能量耗散机制,建立元胞自动机模型,针对镁合金建立了三大晶粒演变规则,研究AZ31镁合金在不同温度和不同时间下晶粒演变规律与边数变化情况,最终获得晶粒均匀分布且以六边形为主的微观组织。通过晶粒长大拓扑学分析与晶粒尺寸分布统计,得出晶粒尺寸在不同温度和时间内呈正态分布,其中六边形晶粒最多;在此基础上,建立固溶情况下的晶粒长大数学模型,合理预测并控制AZ31镁合金固溶后的晶粒尺寸和最终性能,分析了晶粒长大动力学,得出镁合金生长指数为0.87,并通过实验验证了元胞自动机模型的正确性和合理性,为研究镁合金在变形过程中的晶粒演变奠定基础。
Compared with traditional steel, magnesium alloy has many advantages such as small density, lightweight, high specific strength, high specific stiffness, good thermal conductivit and comprehensive performance and it has good application and broad prospects in petrochemical and information industry. However, it is poorly plastic at room temperature, which leads to cracks in the rolling process and affects their quality, therefore it is required to be solution-treated to improve its plasticity before processing. Taking into account this, the original grain structure of AZ31 magnesium alloy tube was obtained by metallographic experiment. Based on the thermodynamic mechanism of grain growth, the mechanism of curvature driving and the energy dissipation mechanism, a cellular automata model and three major grain evolution rules was established. And the grain evolution and edge number of AZ31 magnesium alloy at different temperatures and different times were studied. Finally, the microstructure with uniform grain distribution and hexagonal shape was obtained. Through the topological analysis of grain growth and grain size distribution statistics, it was found that the grain size is normally distributed at different temperatures and times, with hexagonal grains being the most. On this basis, the mathematical model of grain growth under the solid solution condition was established, and its grain size and final properties after solid solution were reasonably predicted and controlled. The analysis of the kinetics of grain growth showed that the growth index of magnesium alloy is 0.87. The correctness and rationality of the cellular automaton model were verified by experiments, which laid a foundation for studying the grain evolution of magnesium alloy during deformation.
Compared with traditional steel, magnesium alloy has many advantages such as small density, lightweight, high specific strength, high specific stiffness, good thermal conductivit and comprehensive performance and it has good application and broad prospects in petrochemical and information industry. However, it is poorly plastic at room temperature, which leads to cracks in the rolling process and affects their quality, therefore it is required to be solution-treated to improve its plasticity before processing. Taking into account this, the original grain structure of AZ31 magnesium alloy tube was obtained by metallographic experiment. Based on the thermodynamic mechanism of grain growth, the mechanism of curvature driving and the energy dissipation mechanism, a cellular automata model and three major grain evolution rules was established. And the grain evolution and edge number of AZ31 magnesium alloy at different temperatures and different times were studied. Finally, the microstructure with uniform grain distribution and hexagonal shape was obtained. Through the topological analysis of grain growth and grain size distribution statistics, it was found that the grain size is normally distributed at different temperatures and times, with hexagonal grains being the most. On this basis, the mathematical model of grain growth under the solid solution condition was established, and its grain size and final properties after solid solution were reasonably predicted and controlled. The analysis of the kinetics of grain growth showed that the growth index of magnesium alloy is 0.87. The correctness and rationality of the cellular automaton model were verified by experiments, which laid a foundation for studying the grain evolution of magnesium alloy during deformation.
引文
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[3]Kugler G,Turk R.Modeling the dynamic recrystallization under multi-stage hot deformation[J].Acta Materialia,2004,52(15):4659-4668.
[4]Timoshenkov A,Warczok P,Albu M,et al.Modelling the dynamic recrystallization in C-Mn micro-alloyed steel during thermo-mechanical treatment using cellular automata[J].Computational Materials Science,2014,94(11):85-94.
[5]Raabe D,Becker R C.Coupling of a crystal plasticity finite element model with a probabilistic cellular automaton for simulating primary static recrystallization in aluminum[J].Modelling&Simulation in Materials Science&Engineering,2000,8(4):445.
[6]Chen F,Cui Z,Liu J,et al.Mesoscale simulation of the hightemperature austenitizing and dynamic recrystallization by coupling a cellular automaton with a topology deformation technique[J].Materials Science&Engineering(A),2010,527(21/22):5539-5549.
[7]Jin Z,Cui Z.Investigation on strain dependence of dynamic recrystallization behavior using an inverse analysis method[J].Materials Science&Engineering(A),2010,527(13/14):3111-3119.
[8]Chu Zhibing,Zhang Duo,Jiang Lianyun,et al.Microstructure model of magnesium alloy AZ31 based on cellular automata[J].Rare Metal Materials and Engineering,2018,47(3):884-894.[楚志兵,张铎,江连运,等.基于元胞自动机AZ31镁合金微观组织模型[J].稀有金属材料与工程,2018,47(3):884-894.]
[9]Ji Haipeng.Prediction of dynamic recrystallization of316LN stainless steel based on cellular automata[D].Qinhuangdao:Yanshan University,2013.[季海鹏.基于元胞自动机法的316LN不锈钢动态再结晶组织预测[D].秦皇岛:燕山大学,2013.]
[10]He Dong.Cellular automaton simulation of grain structure evolution[D].Harbin:Harbin Institute of Technology,2007.[何东.晶粒组织演化的元胞自动机模拟[D].哈尔滨:哈尔滨工业大学,2007.]
[11]Zheng Yi.Simulation of grain growth and recrystallization of LZ50 steel based on cellular automata[D].Taiyuan:Taiyuan University of Science and Technology,2015.[郑毅.基于元胞自动机法的LZ50钢晶粒长大和再结晶模拟[D].太原:太原科技大学,2015.]
[12]He Y,Ding H,Liu L,et al.Computer simulation of 2D grain growth using a cellular automata model based on the lowest energy principle[J].Materials Science&Engineering(A),2006,429(1):236-246.
[13]Ding Hanlin.Experimental study and numerical simulation of high temperature deformation behavior of AZ91 magnesium alloy[D].Shanghai:Shanghai Jiaotong University,2007.[丁汉林.AZ91镁合金高温变形行为的实验研究与数值模拟[D].上海:上海交通大学,2007.]
[14]Ma Xiaofei,Guan Xiaojun,Liu Yunteng,et al.CA model of grain growth based on improved transformation rule[J].Chinese Journal of nonferrous metals,2008(1):138-144.[麻晓飞,关小军,刘运腾,等.基于改进转变规则的晶粒长大CA模型[J].中国有色金属学报,2008(1):138-144.]
[15]Zhang H Q,Wang X F,Wei B L,et al.Effect of tooling design on the cold pilgering behavior of zircaloy tube[J].International Journal of Advanced Manufacturing Technology,2017,92(3):1-15.
[16]Li Xu.Microstructure evolution of TA9 titanium alloy during hot deformation[D].Nanjing:Nanjing University of Aeronautics&Astronautics,2012.[李旭.TA9钛合金热变形过程微观组织演变的研究[D].南京:南京航空航天大学,2012.]
[17]Zhu Peipei.Microstructure simulation of Ti-55 high temperature titanium alloy during hot deformation process based on cellular automata[D].Harbin:Harbin Institute of Technology,2016.[祝培培.基于元胞自动机法的Ti-55高温钛合金热变形过程组织模拟[D].哈尔滨:哈尔滨工业大学,2016.]