Observation of Microstructural Characteristics on the Formability for AA 7075 Alloy Sheets Under Warm Forming Conditions

Various warm forming processes for AA 7075 alloy sheets integrate pre-aging, optimized process parameters, and paint bake treatment to enhance formability while minimizing strength loss. Previous studies link these improvements to matrix precipitates (MPts) characteristics, but mainly focus on post-formed strength rather than formability under warm conditions. This study evaluates the formability of AA 7075 sheets subjected to peak aging, pre-aging, and W-temper using isothermal warm tensile and limit dome height tests. Microstructural features before forming were analysed via transmission electron microscopy and small-angle X-ray scattering. The correlation between microstructural characteristics and formability was then investigated. Results indicate that the product of MPts volume fraction and average radius (fvRavg) has a greater effect on formability than MPts spacing (Sp) in conditions with significant strength differences. This is attributed to the dominant influence of deformation resistance over dynamic recovery, especially when MPts are shearable.