Analytical model for predicting strength of Al alloys: unified multi-mechanistic description applied to friction stir processed, welded, cold rolled and age hardened alloys

Description/Abstract

A unified model based on analytical equations for strength and strength development during processing in a range of Al alloys is reviewed. The model is applied to predict and analyse the strength in a range of thermomechanically processed Al alloys including multicomponent cold-rolled-and-aged alloys, to friction stir (FS) welded and FS processed alloys. Prediction capability is critically tested on groups of alloys in Al-Mg-Cu-Mn-Si and Al-Cu-Mg families of alloys. In the former, solution hardening, dislocation hardening and precipitation hardening provide strengthening contributions of comparable levels, whilst in the latter precipitation hardening is dominant. It is shown that highly accurate predictive models are obtained, with accuracies in the order of 10 MPa. Yield strength due to grain boundary strengthening in FS processed materials is predicted to be nearly always lower than 10 MPa, i.e. in most cases nearly negligible. Notwithstanding the high levels of plastic deformation undergone during FS processing, the contribution of dislocation hardening to local yield strengths of FS processed materials is very low, and much lower than that of cold rolled alloys.