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通过2024-T3和新型2524-T34铝合金的疲劳实验和对试样表面及疲劳断口的观测,研究了材料的微观结构和疲劳裂纹萌生机制。实验在室温下完成,应力比为0.1、加载频率为15 Hz。结果表明:实验材料呈现了再结晶的层状晶粒结构,晶粒沿着轧制方向被拉长,并较为平坦。2024铝合金中二相粒子的分布更为密集无序,且粗大、不规则形状的二相粒子分布更多,而2524铝合金中二相粒子多沿轧制方向呈带状分布。2524铝合金中的多数裂纹萌生于材料中含Fe的粗大的β相粒子,并伴有少量的滑移带裂纹形核和材料缺陷裂纹形核等;包铝层的滑移带形成的挤入挤出为2024和2524包铝合金的裂纹多处形核提供了主要位置。
Through the fatigue test of 2024-T3 and the new type 2524-T34 aluminum alloy and the observation of the surface and fatigue fracture of the specimen, the microstructure and fatigue crack initiation mechanism were studied. The experiment was done at room temperature with a stress ratio of 0.1 and a loading frequency of 15 Hz. The results show that the experimental material presents a recrystallized layered grain structure with the grains being elongated and relatively flat along the rolling direction. In the 2024 aluminum alloy, the distribution of two-phase particles is more disordered and the distribution of coarse and irregular two-phase particles is more. However, the two-phase particles in 2524 aluminum alloy are distributed in strip shape along the rolling direction. Most of the cracks in 2524 aluminum alloy originated from the coarse β phase particles containing Fe in the material, accompanied by a small amount of slip band nucleation and material defect nucleation. Extrusion for the 2024 and 2524 package aluminum alloy crack nucleation provides the main location.