分级电磁搅拌对半固态A356铝合金凝固组织的影响

Effects of Stepped Electromagnetic Stirring on SolidificationMicrostructure of Semisolid A356 Alloy

运用Maxwell计算了分级电磁搅拌下半固态A356铝合金熔体中磁场强度和电磁力的分布与大小,研究了电磁场分布规律以及电磁场对熔体中初生α相形貌演变的影响。结果表明:磁场强度和电磁力由合金熔体中部依次向外递增且前者表现出中间小边缘大的现象,电磁频率和电流强度皆影响合金熔体中电磁力的大小,前者影响程度小于后者,且电流强度的改变可更好地调控熔体初生相的形貌。试验研究结果也表明,应用分级电磁搅拌制备半固态A356合金浆料是可行的且分级搅拌诱发了合金熔体凝固系统的混沌对流,A356铝合金熔体于630℃浇注,并在分级电磁搅拌频率为30 Hz条件下搅拌5 s,20 Hz条件下搅拌10 s,电流强度5 A,并在590℃保温15 min,此制备工艺下可获得较为细小的初生相组织,组织形貌最佳。

The regularities of distribution of the electromagnetic field and influence of the stepped electromagnetic stirring on the primaryαphase of semisolid A356 Al alloy were researched.The distributions of magnetic field intensity and electrostatic force and their values were calculated by Maxwell.The results indicated that the magnetic field intensity and electromagnetic force increased from the centre of the melt to the outside,and the magnetic field intensity was heterogeneous distribution in the system.Both of electromagnetic frequency and current intensity had effects on the electromagnetic force in the melt of alloy,but the effect of electromagnetic frequency was less than that of the current intensity and the change of current intensity can better regulate the morphology of primaryαphase.The results also revealed that it was feasible for semisolid A356 alloy slurry manufactured by the stepped electromagnetic stirring,and the chaotic advection was induced by the stepped stirring in the solidification system of the melt.When the melt of A356 alloy was poured at 630℃,and then stirred for 5 s at 30 Hz,10 s at 20 Hz under the current intensity of 5 A,followed by thermal holding for 15 min at 590℃,the fine primary phase with the good morphology in the semisolid A356 alloy could be obtained by the stepped electromagnetic stirring.