Strength differential effect in age hardened aluminum alloys

Abstract

The strength differential (SD) effect, as reported in literature over the past decades, is a discrepancy between the axial stresses in compression and tension. This study investigates the SD effect in aluminum alloys using both experiments and numerical simulations. We present compressive and tensile tests of four aluminum alloys in several tempers with yield strengths varying from 27 MPa to 373 MPa: a total of thirteen different material configurations. The axial stresses measured in compression tests are significantly higher than corresponding tensile stresses for nearly all material configurations. In our tests, the SD effect generally increases with material strength, indicating that aluminum alloys are pressure sensitive. The physical mechanism responsible for the SD effect was not investigated in this paper, but a plasticity model based on the hypothesis that dislocation motion is affected by hydrostatic pressure, as put forth by several authors, gives an accurate description of the material behavior in compression and tension.