电磁场作用中近液相线铸造ZL201合金的组织及其机理

以ZL201合金为研究对象,采用降低浇铸温度同时施加电磁场的模铸工艺,研究了ZL201合金的凝固组织及组织细化机理.结果表明:在液相线温度附近施加电磁场,合金组织为均匀、细小非枝晶组织;随着电流增大和冷却增强,组织细小、均匀的趋势增强;低过热度浇铸时,临界晶核半径减小,此时在电磁场作用下,熔体的温度梯度降低,促进了准固相原子团簇在熔体中的形成,形核率增大,组织细小、均匀.凝固初期,由于电磁场作用使溶质分布均匀,熔体中晶核向各方向的长大速率趋于一致,晶粒以近球形长大.

On the Microstructure and Refining Mechanism of ZL201 Alloy Prepared by Near-Liquidus Casting in Electromagnetic Field

With the casting temperature lowered properly and an electromagnetic field applied to the preparation of ZL201 alloy, the solidified structure and its refining mechanism were investigated. The results revealed that the alloy is of a homogeneous, fine and non-dentritic crystalline structure which tends to be finer and more homogeneous with the increasing current and enhanced cooling effect. When casting at near-liquidus temperature, the radius of critical crystal nucleus decreases and, meanwhile, the melt temperature gradient decreases under the action of electromagnetic field, thus stimulating the formation of quasi-solid radicals to increase nucleation rate and making the structure finer and more homogeneous. During the initial solidification the growth rates of crystal nuclei in diverse directions tend to the same with grains growing up in sphere-like shape, since the distribution of solutes becomes uniform under the action of electromagnetic field.