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根据优化的激光工艺参数,利用激光冲击处理技术在AZ31B镁合金上制备出纳米结构表层,采用X射线衍射仪(XRD)和透射电镜(TEM)表征了AZ31B镁合金激光冲击处理后表面纳米层的微观结构,分析了纳米晶粒内微挛晶的成因,探讨了激光冲击处理诱导AZ31B镁合金晶粒细化的机理。晶粒细化机理归纳如下:在原始晶粒内,位错滑移导致位错缠结,应力集中诱发机械孪生;在亚晶粒和已经细化的晶粒内,继续形成位错缠结和位错胞;位错缠结转变成小角度取向差的亚晶界,细分粗大晶粒成亚晶粒;亚晶界演变成大角度晶界,最终形成等轴状、取向随机分布的纳米晶组织。
According to the optimized laser process parameters, nanostructured surface layers were prepared on AZ31B magnesium alloy by laser shock treatment. The surface nanostructures of AZ31B magnesium alloy after laser shock treatment were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) The microscopic structure of the microstructures was analyzed. The origin of micro-twin crystals in the nanocrystalline grains was analyzed. The mechanism of grain refinement induced by laser shock treatment on AZ31B magnesium alloy was discussed. The mechanism of grain refinement is summarized as follows: In the original grains, dislocation slip leads to dislocation entanglement and stress concentration induces mechanical twins. In subgrains and refined grains, dislocation entanglement and Dislocation cells; dislocation entanglement into small-angle orientation of the sub-grain boundaries, the subdivision of coarse grains into subgrains; subgrain boundaries into large-angle grain boundaries, the final formation of equiaxed, randomly oriented nano-orientation Crystal organization.