脉冲磁场对7075合金凝固组织的影响

Effect of Pulsed Magnetic Field on Solidification Structure of 7075 Alloy

研究了脉冲磁场作用下7075合金凝固组织的变化,考察了脉冲电压、浇注温度和模具预热温度对合金初生晶粒大小和形态的影响,并对磁场影响凝固组织的机理进行了探讨。结果表明,在脉冲磁场的作用下,7075合金的凝固组织显著细化,其初生相转变为细小的花瓣状或颗粒状晶体;随着脉冲电压从0增大到210V,浇注温度从730℃降至640℃或模具预热温度从600℃降至室温,合金的晶粒平均尺寸逐渐减小;当脉冲电压达到210V时,合金的平均晶粒尺寸约为252μm;浇注温度或模具预热温度越高,合金初生晶粒球化效果越明显;施加脉冲磁场后,晶粒细化的主要机制是电磁搅拌和电磁振荡。

Influences of different pulse voltage, pouring temperature and mold temperature on the solidi- fied structure of 7075 aluminum alloy under pulsed magnetic field were investigated, and the related mechanism was also described. The results show that solidification structure of 7075 alloy can be refined obviously under the pulsed magnetic field. The primary phase of the 7075 alloy is transformed from de- veloped dendrites into rossette-like or spherical crystals. With pulse voltage increasing from 0 to 210 V, pouring temperature decreasing from 730 ℃ to 640 ℃ or mold temperature decreasing from 600 ℃ to room temperature, the average grain size of the alloy is decreased. When pulse voltage is 210 V, the av- erage grain size of the alloy reaches 252 μm. With pouring temperature or mold temperature increases, primary grain in the alloy becomes spherical structure increasingly. The grain refinement mechanism of the alloy is characterized by electromagnetic stirring and electromagnetic oscillation under the pulsed magnetic field.