مشخصات پژوهش

The impacts of various thermo-mechanical process routes in forming of EN AW 7075 alloy on mechanical properties, microstructure and corrosion resistance were investigated. A simulated forming process of two very different conditions, i.e., T6 and W-Temper is the focus of the present study. Irrespective of soaking time and predeformation, specimens quenched in water exhibited superior mechanical properties compared to air-cooled ones. A shorter solution heat-treatment soaking time in the pre-deformed condition, i.e., T6-Temper, caused a drop in the elongation at fracture. Microstructural analysis revealed, regardless of pre-deformation and soaking time, a high fraction of fine η′ strengthening precipitates with stoichiometry close to MgZn upon artificial ageing in the specimens quenched in water. Mechanical properties and microstructural evolution indicate that predeformation of solution heat treated specimens before the ageing treatment, i.e., W-Temper, leads to dislocation multiplication and, eventually, further nucleation sites for precipitation. Thus, forming the W-Temper condition caused very similar resulting mechanical properties and microstructure compared to that of the T6 condition. However, W-Temper forming was found to be detrimental for stress corrosion cracking. Corrosion behaviour of air-cooled specimens was found to be very poor in general. Results obtained in the present work can facilitate the development of thermo-mechanical process routes for EN AW 7075 to eventually tailor mechanical properties, corrosion behaviour and microstructure.