Effect of electromagnetic field on microstructure and macrosegregation of flat ingot of 2524 aluminium alloy

Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effect of electromagnetic field on the microstructure and macrosegregation of this alloy was systematically studied. The results show that the fiat ingot prepared by the LFEC process has a finer and more uniform as-cast microstructure and the grain morphology is transformed from dendrite and rosette-like to equiaxed structure. The LFEC process also shows a significant effect on macrosegregation, and with the application of electromagnetic field during casting process, the segregation in the centre of the ingot is obviously reduced. The mechanism of these effects was also discussed.

Sr-Ca复合变质对A390铝合金微观组织的影响（英文）

研究了Sr-Ca复合变质对A390铝合金显微组织中初生硅相、共晶硅相、初生α相和金属间化合物相数量、尺寸和形貌变化的影响规律。结果表明,Sr-Ca复合变质体现为协同作用,少量Ca的加入不仅减缓了Sr在熔体中的烧损,降低了Sr烧损率,而且抑制了Sr对初生硅相的粗化作用。在A390铝合金中Sr的主要作用是变质共晶硅相和细化θ相,Ca的主要作用是变质初生硅相和初生α相。当联合添加质量分数0.05%Sr-Ca且Sr、Ca原子比为5:1时,获得了最佳组织形态,其中初生硅相、共晶硅相、初生α相均较0.05%Sr单独变质时有明显改善。