Mechanical property and microstructure evolution of aged 6063 aluminum alloy under high strain rate deformation

The dynamic impact tests were performed on 6063 alloy with different initial aging conditions of under-aged (UA), peak-aged (PA) and over-aged (OA) at different strain rates ranging from 1 x 10(3) to 5 x 10(3) s(-1) by split Hopkinson pressure bar. The results show that dynamic deformation behavior is affected by initial aging condition, as well as strain rate. The PA alloy exhibits the highest flow stress and strain rate sensitivity (SRS), while the UA alloy displays the lowest flow stress and SRS. The dislocation and precipitate evolution were analyzed by TEM observations. During high strain rate deformation, the density of the dislocation increases with strain rate, the GP zones in the UA alloy are almost dissolved into the matrix, the number density of the beta precipitates in the PA alloy decreases with increasing strain rate due to the dynamic dissolution. The impact deformation results in a great energy differences between precipitates and matrix, precipitates dissolution occurs in order to balance the disrupted thermodynamic equilibrium. The dynamic evolution of the precipitates has a great effect on the mechanical property of the impacted 6063 alloy, it is necessary to consider the microstructure evolution in material selection and structure design.