356铝合金液相线半连续铸造组织的研究

As-cast Microstructures of 356 Aluminum Alloy Cast by LSC

研究了液相线半连续铸造条件对 35 6铝合金组织的影响·结果表明 ,合金熔体在常规铸造温度 (72 0℃ )下浇注获得的锭坯边部和中心部位的组织都是粗大的枝晶 ,极不均匀 ;在略高于液相线温度 (6 2 5℃ )保温 30min后的铸造组织边部是细小枝晶组织 ,中心部位是均匀的近球形晶粒组织 ;在液相线温度 (6 15℃ )保温后进行半连续铸造获得的锭坯中心和边部组织均是均匀、细小的近球形组织 ,晶粒的平均等积圆直径为 2 5～ 35 μm ,平均圆度为 1.75～ 2 ·另外 ,一次冷却强度的降低、二次冷却强度的增大和铸造速度的减小有利于均匀、细小的近球形组织的形成·

The as cast microstructures of 356 alloy cast by liquidus semi continuous casting (LSC) were studied. When the billet is cast from the normal casting temperature (720?℃), the border and the center microstructures are coarse, dendritic and asymmetry greatly. When the billet is cast upper the liquidus temperature (625?℃) and the melt alloy is held for 30?min, the border microstructures are small dendrites. The border microstructures are net spherical grains. When the billet is cast from the temperature (615?℃) close to the liquidus and the melt alloy is held for 30?min, the border and the center microstructures are the best and there is a little difference between them, but the grains are fine, uniform and globular. The average diameters of the grains are about 25～35?μm and the average circularity is about 1 75～2. In addition, the reduction of the first cooling and the casting velocity,the enhancement of the second cooling are propitious to the formation of the fine, uniform and globular grains.