铝合金铸轧组织的物理模拟

Physical simulation of roll-casting microstructure of Al alloy

设计了铝合金铸轧工艺模拟的实验装置 ,研究了在该试验条件下 ,铝合金变形组织与工艺参数的关系。结果表明 :按照本试验的设计 ,在夹头通水冷却的Gleeble 15 0 0热模拟机上能够得到铝的“人”字形特征的柱状晶组织 ,实现铸轧组织的物理模拟过程。铝合金模拟铸轧的显微组织对外力施加的应变速率很敏感 :ε· =0 .12 5s-1时 ,变形开始与凝固过程发生耦合 ,铸轧组织发生转变 ;应变速率增大至ε· =0 .30 0s-1时 ,铸轧柱状晶发生等轴化。铸轧组织的形成主要是变形作用于未凝固的液相 ,引起质量和热量的分布状态发生改变所致。提高铸轧速度 ,有利于铸轧组织的形成和铸轧柱状晶的等轴化 ,并且使所需的轧制力减小 ,有利于铸轧工艺的优化。

An experimental instrument for simulating the roll-casting process was designed, and the effect of processing parameters on the microstructure of Al alloy was studied. Results show that with a specifically designed instrument equipped in a Gleeble-1500 Thermal Simulation Tester the typical microstructure with the characteristic of realistic roll-casting process can be obtained, and the microstructure is sensitive to the strain rate. When ε·=0.125 s -1, the plastic deformation of Al alloy starts to couple with the solidification process, and the microstructure is of the roll-casting character. When ε·=0.300 s -1, the column crystals transform to equiaxed ones. The formation of roll-casting microstructure is mainly attributed to the deformation of un-solidified liquid phase, the varied distribution of mass and heat. Increasing the deformation velocity would do good to the formation of roll-casting microstructure and the equiaxed column crystals, and would decrease the rolling load.