Strengthening of A5052 aluminum alloy by high-pressure sliding process

A commercial purity of an Al-2mass% Mg alloy (A5052) was processed by severe plastic deformation using high-pressure sliding (HPS) for grain refinement. Mechanical properties and microstructures were examined after the HPS processing and subsequent annealing. Dislocation density decreased and grain growth occurred by the annealing. However, annealing at 150 °C led to an increase in the yield stress \({\sigma }_{y}\) ${\sigma }_y$ to 420 MPa as well as the strain hardening coefficient (n = 0.49) defined in Ludwik’s equation in comparison with \(\sigma_{y} = 375 \;{\text{MPa}}\) ${\sigma }_y=375\text{MPa}$ and n = 0.25 in the as-HPS-processed state. It was shown that a Hall–Petch relation holds with a coefficient, k = 0.16 MPa m^−1/2. The ratio of Vickers harness to tensile stress ( \(Hv /{\sigma }_{{\text{TS}}}\) $Hv/{\sigma }_{\text{TS}}$ ) was ~ 3, while the ratio to the yield stress ( \(Hv/{\sigma }_{y}\) $Hv/{\sigma }_y$ ) was 3.3–4.8. Furthermore, plotting of several SPD methods including this study for tensile strength against equivalent strain resulted in a linear relationship and indicated that the HPS process yielded the highest strengthening. The strengthening mechanism was evaluated for the HPS-processed A5052 alloy so that the dominant contribution to the strengthening was from the grain boundary hardening due to significant grain refinement, which was up to 70% of the total strength.