超声-低频电磁复合物理场作用下对AZ61镁合金半连续铸造凝固组织的研究影响 影响

Effect of compound physical Ultrasonic-Low Frequency Electromagnetic Casting Complex Field on Microstructures of Semi-Continuous Cast AZ61 Magnesium Alloy Billets

摘要:

本文采用不同外场施加方式和半连续铸造制备Φ165mm AZ61镁合金锭坯,研究不同外场施加方式对AZ61镁合金锭坯晶粒尺寸和硬度的影响。结果表明,施加频率为30Hz、电流为60A的交变电磁场后,铸锭边部和中心平均晶粒尺寸由常规DC半连续铸造(DC)的248μm和276μm分别降至196μm和259μm,降低幅度分别达21%和6.2%,边部和中心细化程度差别较大明显不同；而施加超声-低频电磁复合场时,铸锭边部和中心平均晶粒尺寸由常规DC铸造的248μm和276μm分别降至185μm和208μm,降低幅度分别达25.4%和24.6%,中心区域细化程度大幅度提高。另外,与常规DC铸造相比,复合场铸造使合金铸锭的硬度提高且从铸锭边部到中心硬度差别明显减小。可见,超声场-低频电磁复合场半连续铸造弥补了电磁场的“集肤效应”,而电磁场的集肤效应弥补了超声的“聚集作用”,其复合场“取长补短”共同作用显著改善了AZ61镁合金锭坯的内部质量,使凝固组织更加均匀、细小,硬度提高并分布均匀。。另外,与常规DC铸造相比,复合场使合金铸锭的硬度有所提高且分布更为均匀。

Abstract:

Using different external fields application ways, AZ61 magnesium alloy was semi-continuously cast into billets with diameter of 165mm. The effects of the different external fields application ways on the grain size and hardness of AZ61 billets were investigated. The results show that compared with the conventional direct-chill semi-continuous cast billets, the grain size of the AZ61 billets cast reduced from 248μm in the edge and 276μm in the centre to 196μm and 259μm respectively(with a reduce of 21% and 6.2% respectively) by low-frequency electromagnetic field (f=30Hz, I=60A)，the structure in edge and centre refining effects are significantly diverse. However, the grain size in the edge and centre from reduced from 248μm in the edge and 276μm in the centre to 185μm and 208μm respectively (with a reduce of 25.4% and 24.6% respectively) by combining ultrasonic and LFEC, and the structure in centre refining effects were significantly improved. Moreover, compared with the conventional DC casting, the compound physical Field can improve the hardness of the ingot and obviously reduce the different hardness from edge to centre. Therefore, the compound physical Field obviously improved the inner qualities of AZ61 magnesium alloy ingot billet, and the microstructure is markedly refined, so the hardness of ingot uniformly improved.