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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1 T、2 T和3 T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3 T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 microstructure evolution of solid metal matrix composites during pulsed magnetic field impacting was investigated. The microstructure evolution was observed and the mechanism was analyzed. In-situ nano-Al2O3 particles reinforced 7055 aluminum matrix in situ composites were prepared by melt direct reaction. The mean particle size was 42.3 nm. There was no obvious orientation relationship between the particles and the matrix, and there was a high degree of mismatch and internal stress. Steady state. Under the magnetic induction of 1 T, 2 T and 3 T, the sheet composites were impacted by impulse, and the dislocations in the treated samples showed the characteristics of “high density and multimorphology”. The calculation shows that the magnetic pressure of the pulsed magnetic field is less than the room temperature yield strength of the material, and the main inducing factor of plastic deformation is the magneto-plastic effect. In this case, the dislocation has the characteristics of paramagnetic obstacle. The magnetic field reduces the dislocation nucleation energy, promotes the dislocation movement, increases the dislocation density and promotes the release of internal stress. The dislocation density increases as the magnetic induction intensity increases. When the magnetic induction is 3 T, the internal stress is completely released while obtaining the maximum dislocation density. The dislocation topography shows a variety of features, such as linear, wraparound, toroidal and spiral. Among them, ring dislocation is the main mode of dislocation movement and internal stress release, and helps to improve the material strength. In the as-cast samples, the rules of atomic arrangement were found. After the impulse magnetic field impingement processing, misplaced atomic planes, atomic alignment, stacking faults and deforming twins were observed, confirming the existence of plastic deformation. High-density dislocation motion separation formed a fault, the dynamic superimposition of strata formed deformation twin.