行波磁场对ZL205A合金凝固组织及性能的影响

采用下行行波磁场对ZL205A合金进行熔炼,研究不同磁场励磁电流对合金凝固组织和力学性能的影响,并分析了θ-Al_2Cu相的演变规律。结果表明,行波磁场可以细化合金组织,形成细小的近等轴晶凝固组织,提高ZL205A合金的抗拉强度和伸长率,且磁场的励磁电流对凝固组织的细化效果有直接影响。在励磁电流频率为50Hz的情况下,最佳励磁电流在10～20A之间。随着励磁电流增加,θ相在磁场中表现为顺磁性,随着磁感应强度增加,形核过冷度增大,形核率增加,组织碎断细化。励磁电流在10A以下时,磁场产生的电磁推力对θ相尺寸的影响较大。当励磁电流为20A时,磁场洛伦兹力引发的熔体流动会增加熔体粘度,阻碍θ相进一步游离细化。

Effects of Downward Travelling Magnetic Field on Microstructure and Mechanical Properties of the ZL205A

The effects of different magnetic field excitation currents on the solidification microstructure and mechanical properties of ZL205A alloy were investigated by using downward traveling wave magnetic field,and the evolution law ofθphase was analyzed.The results show that the traveling wave magnetic field can refine the alloy structure to form fine near-equiaxed crystal structure,and improve the tensile strength and elongation of ZL205A alloy.Meanwhile,the excitation current of the magnetic field has a direct effect on the refinement effect of solidification structure.With the current frequency of 50 Hz,the desirable excitation current for ZL205A alloy is in range of 10~20 A.In addition,with the increase of the excitation current,theθphase appears to be paramagnetic in the magnetic field.As the magnetic field increase,the nucleation undercooling degree is increased,so the nucleation rate is increased andθphase is broken down.When the excitation current is less than 10 A,the electromagnetic force generated by the magnetic field has a great influence on the size of theθphase.When the magnetic current is 20 A,the melt viscosity is increased as a result of the magnetic field Lorentz force,which can prevent theθphase from further refinement.