中文摘要：

基于高强铝合金在断裂过程中萌生不同尺度微裂纹的机制，用断裂力学建立两种尺度微裂纹影响应力应变场的规律，导出高强铝合金拉伸延性与两种尺度微裂纹的关系，由断裂韧性与拉伸延性的关系建立了高强铝合金断裂韧性与双级微裂纹的非线性关系模型。通过模型解析，分析两种尺度微裂纹体积分数对高强铝合金断裂韧性的影响规律。结果表明：随着一级微裂纹体积分数的增加，材料的断裂韧性开始迅速下降，然后缓慢降低；在较大尺度微裂纹之间萌生小尺度微裂纹，将显著降低合金的断裂韧性。将高强铝合金的结晶相作为一级微裂纹，将弥散相和粗大析出相作为二级微裂纹，预测高强铝合金断裂韧性随两种尺度相（微裂纹）的变化，其规律与实验结果较为吻合。利用模型解析与实验验证结果，提出了改善高强铝合金断裂韧性的组织控制方向。

英文摘要：

A fracture toughness model of high-strength aluminum alloy was established to describe the nonlinear relationship between fracture toughness and two-scale-size microcracks, based on fracture mechanics of two-scale-size microcracks initiated during aluminum alloy deformation and the derived relation between tensile ductility and twoscale-size microcracks. The model shows the effect of volume fraction of two-scale-size microcracks on fracture toughness of aluminum alloy. The fracture toughness of aluminum alloy decreases dramatically and then decreases moderately with the increase of large-scale-size microcracks. The formation of the small-scale size microcracks between the large microcracks decrease the fracture toughness sharply. The model predictions of the fracture toughness evolution of high-strength aluminum alloys with two-scale-size microcracks agree with the experimental data, with the constituents being large-scale-size microcracks and the coarse dispersoids and precipitates being small-scale size microcracks. How to improve fracture toughness of high-strength aluminum alloy was discussed based on this model.