The effect of the thickness on fatigue crack propagation behaviour of rolled and annealed Al-3Mg alloy foils was investigated using notched rectangular specimens with thicknesses of 30 µm and 100 µm and elastic finite element method analysis. A specialized apparatus in combination with a force sensor and a video graphics array digital camera to record the crack growth was employed to investigate the mode I fatigue behaviour of freestanding Al-3Mg alloy foils. Tests were conducted at ambient temperature, with a loading frequency of 2 Hz and a loading ratio R of 0.1. The foil thickness was found to play a distinct role in the fatigue properties of micron-foil metals. Compared to the 100-μm-thick foil, the 30-μm-thick foil exhibited higher average yield stress (σ_0.2), but lower elongation, fracture toughness and fatigue life. The crack propagation rate da/dN of both foils as a function of the stress intensity factor ΔK followed the Paris relationship. The Paris constant m, increased slightly, from 4.6 to 5.6, as the foil thickness decreased from 100 µm to 30 µm. A smaller plastic zone size at the crack tip and a higher value for the self-similarity parameter z were found in the thinner foils, resulting in the higher Paris constant m value. With typical fatigue striations, the 30-μm-thick foils demonstrated failure in a brittle mode during the stable fatigue crack growth stage. However, the 100-μm-thick foils had abnormal striations and dimples in the stable fatigue crack growth stage, they failed in a mixed ductile and brittle mode.

使用厚度分别为30 µm和100 µm的矩形缺口试样以及弹性有限元方法，研究了厚度对轧制和退火的Al-3Mg合金箔的疲劳裂纹扩展行为的影响。结合力传感器和视频图形阵列数码相机的专用设备来记录裂纹的生长，用于研究独立式Al-3Mg合金箔的I型疲劳行为。测试在环境温度下进行，负载频率为2 Hz，负载比R为0.1。发现箔厚度在微米箔金属的疲劳特性中起着显着的作用。相较于100微米厚的箔片，在30微米厚的箔表现出较高的平均屈服应力（σ _0.2），但伸长率，断裂韧性和疲劳寿命较低。两种箔的裂纹扩展速率da / dN随应力强度因子ΔK的变化遵循巴黎关系。当箔厚度从100 µm减小到30 µm时，巴黎常数m略有增加，从4.6增加到5.6。在较薄的箔片中发现裂纹尖端的塑性区尺寸较小，自相似参数z的值较高，从而导致较高的巴黎常数m价值。具有典型的疲劳条纹，厚30μm的箔片在稳定的疲劳裂纹扩展阶段表现出脆性破坏。但是，在稳定的疲劳裂纹扩展阶段，厚度为100μm的箔具有异常的条纹和凹痕，但在延性和脆性混合模式下失效。