脉冲-交流磁场对AZ31镁合金组织及力学性能的影响

Effects of Compound Magnetic Field of Pulsed and Alternate Field on Solidified Structure and Mechanical Properties of AZ31 Magnesium Alloy

采用无磁场的常规铸造处理、施加脉冲磁场、施加交流磁场、施加脉冲-交流复合磁场4种工艺处理方式对AZ31镁合金凝固组织和力学性能的影响进行了分析,另外在施加复合磁场中考察了3种不同工艺参数:脉冲电压、脉冲频率及模具温度对合金的初生相形貌和晶粒尺寸的影响。结果表明,与交流磁场处理或脉冲磁场处理相比,复合磁场处理细化效果最好。经复合磁场处理后,合金的初生相由发达的树枝晶转变为细小的等轴晶,平均晶粒尺寸从3.5 mm减小到0.93mm,断面等轴晶的比例由55.8%提高到97%;复合磁场中随着脉冲电压(0~300V)或脉冲频率(1~10 Hz)增加,初生相由不完整的树枝晶逐渐退化为细小的等轴晶或蔷薇状晶;随模具温度从20℃增加至600℃,复合磁场处理后合金的晶粒尺寸先增大后减小然后再增大,200℃时晶粒尺寸最小。3种磁场处理方式中,复合磁场处理对合金的力学性能提高最明显,与常规铸造相比,合金的抗拉强度与伸长率分别提高了35.8%和25.6%。

Effects of some treating technologies,such as without magnetic field treatment,with pulsed magnetic field treatment,alternate magnetic field treatment and compound treatment of pulsed magnetic field and alternate magnetic field,on solidified structure and mechanical properties of AZ31 magnesium alloy were investigated comparatively.Morphology of primary phase and grain size of the alloy with different pulse voltage,pulsed frequency and mould temperature under the conditions of compound treatment were obserevd.The results show that refinement effect of solidified structure by compound treatment is more efficient than that of pulsed magnetic field treatment or alternate magnetic field treatment.Average grain size of the alloy can be refined from 3.5 mm to 0.93 mm,and the fraction of equixed grains in the alloy can be increased from 55.8%to 97% by compound treatment.With the increase of the pulsed voltage or frequency,primary phase in the alloy is degraded gradually from well-developed dendrites into fine equiaxed grains or rosette crystals.When the mould temperature is at 20~600 ℃,with the increase of mould temperature,solidified structure is refined firstly and then coarsened,and at 200℃,the grain size reaches the minimum value.For three treatment ways,compound treatment exhibits the best effects.Compared with those of conventional casting,tensile strength and elongation of the alloy are increased by 35.8% and 25.6%,respectively.