电磁搅拌对半固态A356-Y铝合金凝固组织的影响

Effect of Electromagnetic Stirring on Microstructure of Semisolid A356-Y Alloy

在A356铝合金中添加少量Y作为合金的细化剂,同时结合自制变频控制的电磁搅拌设备对合金进行短时弱电磁搅拌。分析了电磁频率对A356-Y合金初生α相形貌和尺寸的影响;并利用背散射电子像,探讨了不同电磁频率对半固态A356-Y合金铸锭径向上稀土元素分布的影响。研究表明:液态A356-Y合金经620℃低过热度浇铸,并在频率为30 Hz的条件下搅拌15 s,于590℃保温5 min后,其初生α相的形貌和尺寸达到最佳,其中心部区域晶粒平均等积圆直径为64.95μm,平均形状因子为0.80;边缘区域晶粒的平均等积圆直径为58.97μm,平均形状因子达到0.83。铸锭径向上的区域不均匀性和稀土元素呈靠近模壁含量越高的分布规律,与电流频率、化合物密度、受力等因素相关。

The rare earth Y was added into A356 alloy as a refiner, meanwhile the electromagnetic stirring device, which was controlled by changing the frequency of electric current, was used to stir the A356 alloy for a few seconds. Effects of different frequencies on microstrueture of primary a phase in semi-solid A356- Y alloy were analyzed. And the backscattered electron image was used to discuss the effect of different fre- quencies on the distribution of rare earth along the cast＇s radial direction. The results indicated that the liquid A356 alloy that poured at low superheat temper- ature （620 ℃ ）, was slightly electromagnetic stirred under the condition of 30 Hz and 15 s, then held at 590 ℃ for 5 min, the morphology and grain size of primary ot phase became more desirable. The average equal-area circle diameter of primary α phase in the core area was 64.95 μm and the average shape factor was 0.80; on the contrary, the average equal-area circle diameter of primary ct phase in the edge area was 58.98 μm and the average shape factor was 0.83 The frequency of current, the density of compounds and the force of object borne were all related to nonuniformity of the morphology and grain size of primary α phase and the distribution of RE along the cast＇s radial direction.