Effects of aging state on fatigue properties of 6A01 aluminum alloy

Abstract

The high‐cycle fatigue (HCF) experiments were carried out for different aging states to study the effects of the aging state and yield strength on the fatigue properties of a 6A01 Al alloy. The results show that the 6A01 Al alloy with the highest yield strength at a peak‐aging (PA) state can exhibit the highest fatigue strength in comparison with the overaged (OA) state and the underaged (UA) state. The main reason is that the increased strength of the 6A01 Al alloy at the PA state can improve the plastic deformation resistance and inhibit the fatigue crack initiation. Additionally, the UA has a similar yield strength but a higher fatigue strength compared with the OA, which shows that the aging state also has a significant influence on the fatigue properties. Finally, combined with the previous studies on the 2XXX and 7XXX Al alloys, the effects of the aging state and yield strength on the fatigue properties of Al alloys are summarized.

Low‐cycle fatigue characteristics and fracture behavior of the die‐forged 2014 aircraft wheel

“…In detail, no significant change is observed in the slope of the linear region for specimens, indicating that the difference in microstructure has little effect on Young's modulus. The slight serrated pattern of the ED curve (engineering strain of 0.8–8%) indicates that dynamic strain aging occurs inside the alloy, which is a strengthening phenomenon caused by the interaction of diffusing solute atoms with moving dislocations 46 . It is worth noting that the area enclosed by the stress–strain curve of the TD specimen is larger than that of the ED specimen, indicating that the TD specimen has higher toughness.…”

Effect of Aging on Impact Toughness and Fracture Behavior of Three Wrought Aluminum Alloys

“…The preparation and examination methods of TEM samples are the same as that of the previous studies. [23,27] 3. Experimental Results…”

“…Since the plastic deformability of a material always has an important influence on the initiation and propagation of cracks, [36][37][38][39][40][41] it is reasonable to explain the effect of the aging state on impact toughness from the perspective of the microscopic deformation mechanism. The underaged state with planar slip dislocations can contribute to good plasticity and excellent work-hardening rates, [11,27] which inhibits strain localization caused by dislocation plugging, improving the impact toughness of the alloy. However, for the overaged state, wavy slip dislocations tend to annihilate and aggregated on the second phase, which reduces the work-hardening rate of the aluminum alloy.…”

“…However, for the overaged state, wavy slip dislocations tend to annihilate and aggregated on the second phase, which reduces the work-hardening rate of the aluminum alloy. [11,18,19,27] As a result, strain hardening is largely restrained, and strain localization tends to occur within the grain, reducing the aluminum alloy's toughness at the overaged state. Establishing the link between work-hardening ability and impact toughness helps us to insight into the effect of microscopic deformation mechanisms on impact toughness.…”

“…It is important to note that the 2024 aluminum alloy exhibits a more marked differential in work-hardening rates between the underaged and overaged stages than the 6A01 and 7075 aluminum alloys. This is because the dislocation annihilation is highly accelerated for the overaged state of the 2024 aluminum alloy owing to its dense, large-scale, and intersected second phases that confine the long-range slip of dislocations and prompt the annihilation of dislocations on the phase boundaries for dislocation to annihilate, [23,27,42] as illustrated by the precipitated phase morphologies of the three alloys in Figure 3. This is also reflected in the tensile curves in Figure 5,i.e., compared to the 6A01 and 7075 aluminum alloys, the plasticity of the overaged state is much smaller than that of the underaged state for 2024.…”