【作者】 孙瑞霞；

【导师】 王狂飞；

【作者基本信息】 河南理工大学 ， 材料加工工程， 2010， 硕士

【摘要】 本文建立了碳钢二维等温奥氏体-铁素体相变的元胞自动机(2DCA)模型;应用所建立的等温相变模型,对含碳量分别为:0.1、0.15、0.2、0.25的四种钢在不同等温温度下奥氏体-铁素体相变进行了模拟,并对奥氏体-铁素体相变的形核、长大及粗化三个阶段进行讨论,提出铁素体生长的混合生长算法;最后,建立了三维等温奥氏体-铁素体相变的元胞自动机(3DCA)模型。模拟结果显示:铁素体优先在奥氏体晶界形核,少量铁素体在奥氏体内部形核;随着保温时间的延长,铁素体优先在奥氏体晶界生长;相变温度一定时,等温奥氏体-铁素体相变过程,最终铁素体体积分数取决于相变初期铁素体的生长速度;生长速度大,铁素体最终体积分数大,而铁素体相的长大速度与奥氏体-铁素体相界处奥氏体相一侧碳原子浓度有关,碳原子浓度越大,铁素体相的长大速度越小;15SiMn钢奥氏体相的平衡碳浓度比25SiMn钢奥氏体相的低,15SiMn钢铁素体初始生长速度比25SiMn钢快,因而,最终铁素体体积分数较大。混合生长算法的提出简化了模型,加快了计算的速度;3DCA模拟结果再现了相变过程中的组织演化过程,三维模型对于晶体相变过程中奥氏体初始状态的不规则性,晶粒形核的随机特性,铁素体长大和粗化等各方面都作了充分地展现,进一步印证了本文的3DCA模型的正确性、可行性。更多还原

【Abstract】 A two-dimensional musicales cellular automaton model (2DCA) is developed to simulate the microstructure formed during the austenite to ferrite transformation in steels. The austenite to ferrite transformation at different isothermal temperatures in two low carbon steels of 0.1、0.15、0.2、0.25 is simulated using the present mode. Especially the grain from austenitic changes to the ferrite of the three stages: nuclear, Growth and coarse mixture of growth and proposed algorithm. Finally, a three-dimensional cellular automaton model (3DCA) is developed to simulate the microstructure formed during the austenite to ferrite transformation.The simulations show: Priority ferrites nucleate in austenite-ferrite interface, and while a small amount of ferrite grain within the austenite nucleation. With the extended holding time, Priority ferrites grow in austenite-ferrite interface. The simulations show: At a given isothermal temperature, the final volume fraction of ferrite grain is determinated by the average original growth rate of ferrite grain during the austenite to ferrite transformation in steels. The mean growth rate of ferrite grain increases and the simulated final ferrite volume fraction also increases. And the mean growth rate of ferrite grain is affected by percentage composition of carbon in steels during the austenite to ferrite transformation in steels. Percentage composition of carbon in steels increases and the mean growth rate of ferrite grain reduce. Because the percentage composition of carbon in 15SiMn steel is lower than 25SiMn steel, and the mean growth rate of ferrite grain in 15SiMn steel is faster than 25SiMn steel, the simulated final ferrite volume fraction increases.The simulation of mixed growth algorithm show: model is simplified and speed of the calculation is accelerated. The simulations of 3DCA show: Organizational evolution during the austenite to ferrite transformation. The initial irregular nature of austenite, grain nucleation of random features, and length large coarse ferrite for three- dimensional cellular automata 3DCA model are externalized. And three- dimensional cellular automata 3DCA model is exact.更多还原