CAJ | 학술논문

铝基复合材料在加入颗粒相之后,延伸率和塑性变形能力明显降低.为改善其塑性变形能力,通过对比强脉冲磁场冲击处理前后试样内部组织和残余应力的变化特征,研究了磁致塑性效应对铝基复合材料塑性变形能力的影响机理.结果表明：当磁感应强度从2T变化到4T时,铝基复合材料中位错密度显著增加,4 T时的位错密度是未加磁场时的3.1倍；3 T,30个脉冲处理后的复合材料中残余应力值从未加磁场时的41 MPa减小为?1 MPa.从原子尺度来看,强磁场导致了磁致塑性效应,从而引起了位错的运动,并促进了位错的退钉扎和可移动位错数量的增加；从材料内部整体结构变化来看,磁场加速了材料内应力的释放速率,降低了材料内部的残余应力,从而改善了铝基复合材料的塑性变形能力.
려기복합재료재가입과립상지후,연신솔화소성변형능력명현강저.위개선기소성변형능력,통과대비강맥충자장충격처리전후시양내부조직화잔여응력적변화특정,연구료자치소성효응대려기복합재료소성변형능력적영향궤리.결과표명：당자감응강도종2T변화도4T시,려기복합재료중위착밀도현저증가,4 T시적위착밀도시미가자장시적3.1배；3 T,30개맥충처리후적복합재료중잔여응력치종미가자장시적41 MPa감소위?1 MPa.종원자척도래간,강자장도치료자치소성효응,종이인기료위착적운동,병촉진료위착적퇴정찰화가이동위착수량적증가；종재료내부정체결구변화래간,자장가속료재료내응력적석방속솔,강저료재료내부적잔여응력,종이개선료려기복합재료적소성변형능력.
For aluminum matrix composite, the introduced particles will strengthen the matrix, but as the obstacles, the heterogeneous particles will hinder the dislocation movement, generate uneven material structure, and may become a source of stress concentration. Therefore, they are detrimental severely to the elongation and plasticity of composite. It is known that dislocations exhibit a paramagnetic behavior because they contain paramagnetic centers including localized electrons, holes, triplet excitons, ion radicals, etc. The initial radical pair of the dislocation-obstacle S (spin angular momentum)=± 1/2 is in a singlet state, and the total spin of the radical pair is 0 and in the antiparallel spin direction, offsetting a magnetism of the radical pair. The magnetic field can change the spin direction from singlet state to triplet state. In the triplet state the electron spin is 1 and in the same spin direction. A strong bond of the dislocation-obstacle is formed only in the singlet state when the spins of the two electrons are antiparallel. So an obstacle is able to pin a dislocation only if the radical pair is in the singlet state. Under the condition of high pulsed magnetic field treatment (HPMFT) the conversion of electronic spin will be a fundamental cause of dislocation motion along a glide plane. The movement of pinned dislocations will change the material microstructure and influence the performance of material. By comparing the microstructural evolutions and the residual stresses of samples subjected to HPMFT with different values of magnetic induced density (B), the positive influence of magnetoplastic effect on the plasticity of aluminum matrix composite is investigated in this paper. The results show that the dislocation density is significantly increased when B changes from 2 T to 4 T. When B = 4 T the dislocation density is enhanced by 3.1 times compared with that of the sample without HPMFT. Moreover, the residual stress is reduced apparently from 41 MPa (B = 0) to ?1 MPa (B=3 T). In the view of atomic scale, the high magnetic field leads to a magnetoplastic effect which contributes to the dislocation movement and promotes the dislocation depinning, thereafter, the number of movable dislocations increases up. From the viewing of the internal structure of composite, the magnetic field accelerates the releasing rate of internal stress and lowers the residual stress in material, which is beneficial to improving the plasticity of aluminum matrix composite.