Increasing the Mechanical Strength and Corrosion Resistance of Aluminum Alloy 7075 via Hydrostatic Extrusion and Aging.

The present study investigates the correlation between mechanical properties and resistance to corrosion of hydrostatically extruded aluminum alloy 7075. Supersaturated solid solutionized samples undergo a plastic deformation process, followed by both natural and artificial aging. Furthermore, two types of hydrostatic extrusion are applied to the samples: single-stepped and double-stepped. This process is shown to influence grain refinement and the precipitation process, resulting in changes in the electrochemical properties of the samples. Hydrostatic extrusion combined with aging is shown to cause an increase in mechanical strength ranging from 50 MPa to 135 MPa in comparison to coarse-grained sample subjected to T6 heat treatment. The highest value of tensile strength is obtained for a sample subjected to single-step hydrostatic extrusion followed by natural aging. This strength increase is caused by refinement of the microstructure, in addition to the small size and number of precipitates at the grain boundaries, which are coarsened by artificial aging. Hydrostatic extrusion is also shown to increase resistance to corrosion, with the T6-treated coarse-grained sample being most susceptible to corrosion attack.