Evolution of Tensile Properties in AA2219 Plates Due to Varying Modes and Percentages of Cold Work before Artificial Aging

Abstract

Evolution of tensile properties in 8-mm-thick AA2219-T8X plates with the pre-artificial aging (here onward termed pre-age) cold work applied independently by cold rolling and stretching was monitored by tensile tests. It is shown that the desired minimum 0.2% proof stress (0.2% PS) of 352 MPa, ultimate tensile strength of 441 MPa and percentage elongation of 7 in T87 temper could be achieved in the longitudinal direction of the alloy following 6% of pre-age cold work by stretching. However, these minimum tensile properties could be achieved in both longitudinal and long transverse directions following 7% of pre-age cold work independent of the methods by which the cold work is employed. The tensile strength properties subsequently decreased when the percentage of pre-age cold work equaled or exceeded 8%. The coarsening of θ′ (metastable Al2Cu-θ) precipitates caused the decrease in strength. It is further observed that suitable percentages of pre-age cold work involving both cold rolling and stretching not only provide the minimum desired T87 tensile properties but considerably reduce the differences in 0.2% PS values between longitudinal and long transverse directions of the plates. This is discussed in terms of the tendency of the pre-age cold work by stretching to introduce directional properties in the plates.