合金枝晶生长及微细界面热质传递模拟

利用元胞自动机法(CA)耦合对流和热质传递模型模拟了Al-Cu二元合金微观组织在多种影响因素下的二维生长过程,分析了枝晶凝固、微界面热质传递以及微流动等微细现象之间的相互作用,得到了单枝晶以及多个枝晶在微流作用下的生长规律。模拟结果表明:(1)枝晶凝固过程中溶质富集于生长前沿。随着枝晶生长,凝固前沿远离冷源,枝晶尖端温度逐渐增大,而浓度逐渐变小;(2)流动对于枝晶的生长有着重要影响。流动破坏了枝晶生长的对称性,下游溶质浓度大于上游,枝晶在上游方向优先生长,而在下游方向有所抑止;(3)多个枝晶生长时,枝晶彼此间有阻碍生长的作用,二次枝晶臂的形成相对减少,枝晶间几乎不存在微流动。

Simulation Of Micro-heat and Mass Transfel with Dendritic Growth in a Binary Alloy

Two dimensional microstructural evolution of a Al-Cu binary alloy during solidification under some factors is simulated by Cellular Automaton method coupling with the model of describing convection,heat and mass transfer.The interactions among dendritic solidification,micro heat and mass transfer and micro fluid flow are investigated.The time evolution of single and multiple dendritic crystals are obtained considering the effects of micro flow.It turns out that:(1)Solutes enrich at the front edge of the growth during dendritic solidification.With the solidification evolution,the temperatures of dendritic tips increase gradually with the decreasing of solute concentration as the dendritic front goes away from the cooling source.(2)Micro convection has great impacts on dendritic growth.The symmetry of dendritic growth is broken by convection.The concentration of the dendritic tip at lower reaches is higher than that at the upstream so that the dendritic growth is preferential at the upriver while restrained at the lower river.(3)Interactional growth-impeding phenomena occur as several dendrites grow simultaneously,accordingly,the formation probability of the secondary dendrite arms decreases relatively.And,there barely exists micro fluid flow between the dendrites.