Method to decode stress-strain diagrams to identify the structure-strength relationships in aged aluminum alloys

Abstract

Leading-edge infrastructure renovation is driven by innovations in materials processing to optimize desired properties. The immediate challenge for the metal industry is the development of effective and efficient materials quality-control practices. At present, mechanical and sheet forming properties are assessed using standard tensile tests to measure yield and ultimate tensile strengths, as well as the total elongation to failure. The resulting stress-strain data is used as a “pass-fail” test to ensure that the product meets industry specifications. We report a new method of constitutive relation analyses (CRA) that can extract fundamental information regarding the underlying crystalline mechanisms of deformation and failure from standard stress-strain data. The CRA method is applied to industrial extrusion product made from AA6063 aluminum alloy to demonstrate how this type of forensic examination can be used to direct changes to thermo-mechanical processing to optimize desired material properties. The CRA prediction of point-defect generation and nano-void formation leading to ductile failure during plastic flow was validated by small angle X-ray scattering (SAXS) studies.