国产与进口5083-H116铝合金微观组织及疲劳裂纹扩展速率研究

研究了国产与进口5083-H116态铝合金轧制薄板材（厚度3 mm）的微观组织及其疲劳裂纹扩展行为。结果表明，国产与进口5083铝合金化学成分均满足相应标准要求。国产与进口5083铝合金显微组织均存在较多的粗大第二相，但后者的数量更多；相对于国产合金，进口合金晶粒尺寸更加细小、分布更加均匀。沿板材横、纵向，国产合金的抗拉强度和屈服强度皆高于进口合金，而延伸率相反。进口合金的疲劳裂纹扩展速率低于国产合金，在ΔK=15 MPa·m^1/2时，其裂纹扩展速率降低了32%以上。疲劳断口皆呈3个典型区域：裂纹萌生区均出现疲劳辉纹，相对于进口合金，国产合金较平坦且存在分层现象；稳态扩展区皆有明显疲劳辉纹，辉纹间距分别为0.405 5μm和0.282 3μm；瞬断区内，进口合金具有数量更多、尺寸更小的韧窝。

Microstructures and Fatigue Crack Growth Rates of Domestic and Imported 5083-H116 Aliuminum Alloy

The microstructures and fatigue crack growth behavior of domestic and imported 5083-H116 aluminum alloys were researched. Experimental results showed that the chemical constitutions of domestic and imported 5083-H116 aluminum alloys both met the standard requirements. Both of the microstructures of do mestic and imported alloys contain a lot of coarse second phases, and the latter more. The grain size and distribution of imported alloy were apparently smaller and more uniform than those of domestic alloy. Compared with the imported alloy, domestic alloy had higher tensile strength and yield strength and lower elongation. The fracture analysis showed that the fracture was both featured with three typical regions. Fatigue striations were observed in both alloys at the crack initiation area, and the area in domestic alloy presented delamination and was flatter than the imported one. The fatigue crack growth rate of imported alloy was lower than that of domestic alloy, and the crack growth rate of imported alloy decreased by more than 32% when ΔK=15 MPa·m1/2. Obvious fatigue striations were observed at the crack propagation area, and the intervals were respectively 0.405 5 μm and 0.282 3 μm. At the transient break area, the imported alloy had more and smaller dimples.