交流磁场下7075铝合金液相线和固相线温度变化

在7075铝合金凝固过程中施加频率为50Hz的交流磁场,磁场强度的变化范围为0 06T,0 09T,0 12T·运用双电桥法分别测定了上述凝固过程的电阻 温度曲线,确定了合金在不同磁场条件下凝固的液相线和固相线温度·实验结果表明:在交流磁场中凝固的合金,其液相线和固相线温度均明显提高,并且结晶温度间隔变小,磁场强度越大,这种变化越明显·与未加磁场的合金相比,经交变磁场处理后的合金,其液相线温度上升了7 5～12 5℃,固相线温度升高了10～20℃·交流磁场作用改变了固液界面前沿液相中的原子团簇向固相跳动时所需克服的势垒,最终导致合金熔点的改变·

Influences of an Alternate Magnetic Field on the Liquidus and Solidus Temperatures of 7075 Al Alloy

Solidification of 7075 Al alloy was investigated in an alternate magnetic field with frequency being 50 Hz and density being 0.06 T, 0.09 T and 0.12 T, respectively. The Resistance-Temperature curves of the solidifications were measured with the method of double bridges to examine the liquidus and solidus temperatures of the alloy under different conditions. It is found through the experiments that, when the alloy is solidified in an alternate magnetic field, its liquidus and solidus temperatures increase obviously and the solidification interval diminishes. The stronger the magnetic density is, the more evident the effects are. Compared with the alloy solidified without a magnetic field, the liquidus temperature increases 7.5-12.5°C and the solidus temperature increases 10-20 °C by the alternate magnetic filed. It is suggested that the barrier potential required by the atom cluster jumping from liquid phase to solid phase at the front of liquid-solid interface is decreased by the alternate magnetic filed.