Influence of Different Cycle Strain Amplitudes on the Microstructure and Properties of 2024 Aluminum Alloy

Abstract

The effect of varying strain amplitudes on the tensile properties and microstructure of aluminum alloy 2024 after a solution treatment (ST) of 495 °C for 1 h followed by cyclic strengthening at room temperature in the presence of various strain amplitudes is methodically investigated. Cyclic strain treatment substantially leads to the enhancement of the strength and plasticity of the alloy. Different strain amplitudes result in distinct toughening mechanisms in the tested specimens. The specimens treated with low strain amplitudes (=0.1-0.4%) exhibit the least changes in the dislocation cell size and the dislocation density. The strengthening is mainly attributed to the precise adjustment of solute cluster precipitation. In specimens treated with high strain amplitudes (=0.5-1.1%), various strain amplitudes result in various dislocation cell shapes. The S-phase precipitation occurs selectively in the dislocation cell walls, forming solute cluster-composite dislocation loops within the dislocation cells, enhancing both the strength and plasticity of the alloy. The rational cyclic strain treatment not only yields the achievement of the precise control of precipitate phases, but also regulates the dislocation configurations. The obtained results reveal that the high-density composites are capable of resolving the conflict between increasing dislocation density and reducing dislocation pile-up, providing new insights into alloy strengthening.

Keywords: Aluminum alloy 2024, Cyclic strengthening, Cycle strain amplitudes, Toughening mechanisms, strength and plasticity, Solute cluster-composite dislocation loops