Simulation of Magnesium Alloy AZ91D Microstructure Using Modified Cellular Automaton Method

A two-dimensional modified cellular automaton model was developed to simulate the solidification process of magnesium alloy. The stochastic nucleation, solute redistribution, and growth anisotropy effects were taken into account in the present model. The model was used to simulate the grain size of magnesium alloy AZ91D for various cooling rates during the solidification process. To quantitatively validate the current model, metallographic experiments were carried out on specimens obtained from sand mold AZ...     

铝合金半连续铸造过程中的液穴温度分布

针对生产一线对于铸锭质量控制和优化生产工艺的需求,在工厂实际生产平台上通过实验方法,测量了热顶立式半连续铸造圆铸锭液穴内部和凝固部分各个不同位置的温度,并通过插值方法得到了整体的温度分布,分析了糊状区的分布特点。结果表明热帽对保持铝液的温度起着明显的作用,结晶器一次冷却区的冷却速度不大,铸锭在凝固过程中散热主要通过二次冷却区冷却水的激冷作用实现。该文结果为工艺参数的优化提供了参考。     

A Modified Cellular Automaton Method for the Modeling of the Dendritic Morphology of Binary Alloys

Introduction The solidification microstructure of a casting is closely associated with the mechanical properties of the final product, which has led to extensive theoretical and experimental studies in this area. However, because of its complexity, the fo…     

Static and Metadynamic Recrystallization of Low Carbon Steels During Mechanical Deformation

Static and metadynamic recrystallization models were developed with the coefficients determined by multiple nonlinear regression analyses to describe microstructure evolution in low carbon steels.The effects of initial grain size, deformation temperature, strain, and strain rate on the austenitic recrystallized volume fraction and grain size were studied using a Gleeble machine. The results show that deformation reduces the grain size when the recrystallized volume fraction is large. The static recrystallized volume fraction increases with increasing deformation temperature, strain, and strain rate, and decreasing initial grain size. The grain size during metadynamic recrystallization is independent of the deformation strain and the initial grain size. The recrystallized volume fraction, the grain size, and the grown grain size calculated by the correlations are consistent with the measured values.     

Dendritic Morphology Simulation Using the Phase Field Method

Dendritic morphology was simulated using a macro- and micro-coupled method. Since the microstructure of a whole casting cannot be easily analyzed, a scheme was developed to calculate the temperature of the whole casting with the microstructure analyzed by selecting one cell in the central region of the casting. The heterogeneous nucleation was described using a Gaussian distribution with the dendritic growth controlled by the solution of the phase field equation. The initial temperature distribution in the microdomain was obtained by interpolating the cell temperatures near the selected cell with the interface undercooling assumed to be the sum of thermal, solute, and curvature effects. The solute distribution was calculated from the mixed solute conservation equation with noise introduced to produce the side branches. The simulation results agree well with experimental results.     

用改进的 SOLA-VOF 法模拟铸造充型过程

铸造充型过程对铸件质量的影响很大，文中对流体充型过程的数值模拟做了研究。以ＳＯＬＡ－ＶＯＦ法为基础提出了改进算法。在三维自由表面处理上，提出一种简单而实用的方法，对原算法的累积流量误差做了修正，方程求解改用预处理共轭梯度法，保证了解的收敛性。为了模拟紊流现象，引入了Ｋ－ε双方程模型，用实验验证这些改进的效果，又用国际会议的标准检验实验进行了验证，着重于紊流现象的分析，模拟结果与验证实验吻合较好。     

铸造充型过程初始温度场的数值模拟及实验研究

对铸造充型过程进行数值模拟是铸造计算机辅助工艺设计的重要内容之一。对铸件充型过程的流场温度场变化及初始温度分布进行了数值模拟研究。在计算方法改进方面，以二维ＶＯＦ方法为基础，提出了一种简单实用的三维自由表面处理技术。用显式热焓法求解能量方程，显著缩短了计算时间。为验证这些计算方法，以灰铸铁试件为例，对其初始温度场进行了重复测试。模拟结果与实测结果吻合较好。