Fatigue Crack Growth Behavior of Al-4.41Cu-0.69Mg-0.64Si-0.52Mn Alloy Forged at Different Temperatures
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The fatigue crack growth (FCG) behavior of T6-aged Al-4.41Cu-0.69Mg-0.64Si-0.52Mn alloys forged at 350°C and 450°C were analyzed. FCG rate tests revealed that the alloy forged at 350°C exhibited a higher fatigue crack threshold (ΔKth) and lower FCG rate in the near-threshold region but a higher FCG rate in the Paris and instability regions than the alloy forged at 450°C. Examination of the crack paths suggested that intergranular propagations were predominant in the near-threshold region, and more crack deflections at grain boundaries contributed to the lower FCG rate of the recrystallized sample forged at 350°C. In the Paris and instability regions, transgranular propagations were predominant, and the lower FCG rate of the non-recrystallized sample forged at 450°C was attributed to the crack deflections between the dislocation walls and sub-grain boundaries.
This work was supported by the National Natural Science Foundation of China (Grant Number 51301209).