研究了脉冲磁场冲击处理时固态金属基复合材料的组织演变规律,观察微观组织演变并进行了机制分析.通过熔体直接反应法制备了原位纳米Al2O3颗粒增强7055铝基原位复合材料,颗粒平均粒径42.3 nm,颗粒与基体无明显取向关系,存在较高错配度和内应力,处于结构失稳状态.在磁感应强度1T、2T和3T条件下对片状复合材料进行脉冲冲击处理,处理后的试样中位错表现出“高密度、多形貌”特征.计算表明,脉冲磁场的磁压强小于材料的室温屈服强度,塑性变形的主要诱因是磁致塑性效应.此时位错具有顺磁性障碍的特征,磁场降低位错形核能、促进位错运动、提高位错密度并促进内应力释放,位错密度随磁感应强度增加而增加.磁感应强度为3T时,在得到最大位错密度的同时完全释放内应力.位错形貌呈现出多样化特征,有线型、缠绕型、环型和螺线型等,其中环型位错是位错运动和内应力释放的主要模式,并有助于提高材料强度.在铸态试样中原子排布规则,脉冲磁场冲击处理后出现了错排原子面、原子排列转向、层错和变形孪晶组织,证实了塑性变形的存在.高密度位错运动分离形成了层错,层错动态叠加形成了变形孪晶.
The structural evolution of the solid metallic composites subject to pulsed magnetic field has been investigated.The in situ nanometer Al2O3 particles reinforced 7055 aluminum alloy have been fabricated.The average size of endogenous particles is 42.3 nm.On the condition of 1 T,2 T and 3 T the flake composite samples were processed by pulsed impact.In the treated samples the dislocation exhibits some specific characteristic as high density and diversity.It is analyzed that the magneto-plastic effect is the main reason that lowers the nucleation energy,accelerates the movement and increases the density of dislocations,facilitates the relief of massive internal stress.The dislocation density increases with the enhancement of magnetic induced intensity and when it equals to 3 T the maximum density is acquired.The morphology of dislocation displays as aligned,tangled,annular and spiral ones.The disordered atomic layer,deflected orientation,stacking fault and deformation twinning can also be seen.It is deduced that the dissociation of high density dislocation facilities the stacking fault and the overlap of stacking fault does the deformation twinning.
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