Inelastic Deformation of an Aluminum Alloy under Combined Stress at Elevated Temperature

摘要

Biaxial stress tests were performed on thin wall tubes of polycrystalline 2024-T81 Aluminum at temperatures of 150 and 250c. The nominal metallurgical stabilization temperature for this alloy is 190c. Transient and steady state creep strain rates exhibited a considerable depenence on load path history. For a prescribed history it is possible to determine unique surfaces of constant creep strain rate. For the zero history, involving a single loading from the origin to a prescribed point in stress space, surfaces of constant steady state strain rate, at elevated temperature, have the same shape as room temperature yield surfaces of moderate offset. In the temperature and small strain regions considered here, room temperature yield surfaces were found to be unaffected by elevated temperature deformation. The changes in shape of room temperature yield surfaces, due to room temperature plastic deformation caused corresponding changes in the elevated temperature surfaces of constant steady state creep rate. At a given stress point, an outward local motion of the yield surface resulted in a corresponding outward local motion of the steady state creep rate surfaces. The experimental determination of surfaces of constant flow potential was also attempted. (Author)