Abstract
The present study investigated grain growth, recrystallization, and fatigue crack growth behavior of Al-Cu-Si alloy subjected to cryorolling and annealing treatment for 1 h. Temperature from 373 to 523 K was considered for this study. Cryorolling is used to produce ultra-fine-grained (UFG) structures, while annealing is used to study the recrystallization and grain growth. The fatigue crack growth (FCG) rate was measured in the low-stress intensity factor range (Δ K) (Stage II) and high-stress intensity factor ranges using the Paris equation and measuring the striation width. The results discovered that cryorolling led to a significant decrease in the fatigue crack growth resistance in the low-stress intensity factor range compared to coarse grain counterparts due to a decrease in the crack closure level in the cryorolled alloy. The results also showed that the fatigue crack growth resistance of the cryorolled alloy improved in the high-stress intensity factor range due to the formation of ultra-fine-grained microstructure, resulting in fine striations observed from the fractographic studies. The post-annealed samples at 373 K exhibited higher fatigue crack growth resistance in low and high-stress intensity factor ranges. High fatigue cracks growth resistance in the annealed sample in low and high-stress intensity factor range is attributed to the fine semicoherent spherical phase θ'.

Key words
Al alloys, cryorolling, annealing, fatigue crack growth rate, fractography

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