Microstructure Evolution and Recrystallization Behavior During Hot Deformation of Spray Formed AlSiCuMg Alloy

Wrought Al-Si alloy has partially replaced the traditional wear-resistant alloy for structural weight reduction owing to the excellent comprehensive properties, such as wear resistance, low coefficient of thermal expansion, and high specific strength. The deformation aluminum alloy based on Al-Si binary alloy is widely used in aerospace and automotive industries. The hot compression test, SEM, TEM, and EBSD technologies were used to investigate the microstructure evolution and dynamic recrystallization nucleation mechanism of spray formed Al25Si4Cu1Mg (mass fraction, %) alloy. The results show that the as-sprayed microstructure consists of equiaxed alpha-Al, coarse Si phase, AlSiCuMg phase, and Al2Cu phase with different scales. Under 623-723 K and 0.001-5 s(-1), the fine Al2Cu phases gradually dissolve with the increase in deformation temperature. During high strain rate (5 s(-1)) compression, dislocation accumulation causes a high degree of stress concentration in front of the coarse and insoluble primary phases, resulting in the cracking of some brittle primary phases. Local cracks also appear at the interfaces between alpha-Al and primary phases. The alpha-Al phase undergoes complete dynamic recrystallization. The recrystallized grain size decreases with the increase and decrease in strain rate and deformation temperature, respectively. The residual dislocation and deformation substructure in the grain decrease with the increase in deformation temperature. The random texture demonstrates that the dynamic recrystallization mechanism of spray formed Al25Si4Cu1Mg alloy is "particle stimulated nucleation (PSN)".