强磁场对铝基复合材料中位错密度的作用机制

Mechanism of high magnetic field on aluminum matrix composites dislocation density

通过原位内生颗粒法制备Al_2O_3和Al_3Ti多相增强7055铝基复合材料,Al_2O_3颗粒粒度,处于纳米级;Al_3Ti颗粒粒度处于微米级,颗粒分散均匀,界面湿润性好。在常温下对铝基复合材料进行脉冲强磁场处理,使磁感应强度B控制在1,2,3,4和5 T,研究不同B下复合材料组织特征变化。研究结果表明:处理后试样的有效微应变和位错密度随磁感应强度的升高而增大。当B=5 T时,有效微应变和位错密度的增加趋势明显减缓,有趋近于饱和之势。位错密度的增加并不是磁压强和磁场力的作用,而是磁场诱发磁致塑性效应。磁场影响量子尺度电子和原子的运动,增强原子的扩散速率和位错间的相互作用,降低位错形核的动力学势垒,促进位错大量增殖。但随着微应变的增加,晶体内部的阻力不断增大,位错密度逐步趋于饱和。

The in-situ Al2O3 and Al3Ti multi-phases reinforced 7055 aluminum matrix composites were fabricated. The particle size of Al2O3 was at nanometer level and that of Al3Ti was at micron level. The particles dispersed evenly in the matrix and the interface exhibited better wettability. Then the composites were processed in high pulsed magnetic field at room temperature. The magnetic induction intensity B was controlled at 1, 2, 3, 4 and 5 T separately. The results show that the dislocation density（ρ） and effective microstrain e increase with B enhancement. When B=5 T, ρ and e tend to be saturated. It is shown that the increase of ρ is not attributed to magnetic pressure or magnetic force while magnetoplasticity effect is induced by high magnetic field. That is to say, the magnetic field influences the movements of electrons and atoms in quantum scale, which enhances the atomic diffusion rate and interactions between dislocations.It reduces the dislocation nucleation kinetic barrier, which makes the dislocation multiply. However, the resistance force in inner crystal increases with the increase of microstrain, which leads to the saturation of dislocation density.