利用透射电镜和高分辨透射电镜(HRTEM)研究了高压扭转大塑性变形纳米结构Al–Mg合金中的位错和晶界结构。结果表明:对尺寸小于100 nm的晶粒,晶内无位错,其晶界清晰平直;而尺寸大于200 nm的大晶粒通常由几个亚晶或位错胞结构组成,局部位错密度可高达1017m-2,这些位错往往以位错偶和位错环的形式出现。用HRTEM观察到了小角度及大角度非平衡晶界、小角度平衡晶界和大角度Σ9平衡晶界等不同的晶界结构。基于实验结果,分析了局部高密度位错、位错胞和非平衡晶界等在晶粒细化过程中的作用,提出了高压扭转Al–Mg合金的晶粒细化机制。 The dislocations and grain boundary structures in high-pressure torsional plastic deformation nanostructured Al-Mg alloys were investigated by transmission electron microscopy and high-resolution transmission electron microscopy (HRTEM). The results show that there is no dislocation in the grain and the grain boundaries are clear and straight for the grain size less than 100 nm. The large grains with the size larger than 200 nm usually consist of several subgrain or dislocation cell structures, The density can be as high as 1017m-2, and these dislocations often appear in the form of dislocations and dislocations. The different grain boundary structures such as small-angle and large-angle non-equilibrium grain boundaries, small-angle equilibrium grain boundaries and large-angle Σ9 equilibrium grain boundaries were observed by HRTEM. Based on the experimental results, the effects of local high-density dislocations, dislocation cells and non-equilibrium grain boundaries on the grain refinement process are analyzed. The grain refinement mechanism of high-pressure twisted Al-Mg alloy is proposed.