Influence of Polycrystalline Structure on Dynamic Strength and Fracture Character of an Aluminum Alloy in Different Welding Joint Zones

Plastic strain localization and fracture in the nugget and thermo-mechanically affected zone of a friction stir welded Al6061-T6 alloy are numerically investigated. Dynamic boundary-value problems are solved by the finite-difference method. A procedure for generating ordered and disordered polycrystalline microstructures experimentally observed in different weld zones is developed. A physically-based relaxation constitutive equation is developed to describe dynamic thermomechanical response of the aluminum alloy. Calculations of microstructure tension in polycrystals are performed. The effect of the degree of order and strain rate on the material dynamic strength and fracture are studied.