Hall–Petch and Hollomon modeling for microalloyed 2219Al alloys under different thermo-mechanical treatments

Present study is aimed at developing Hall–Petch and Hollomon models for 2219Al alloys microalloyed with varying Cd contents (up to 0.1 wt%), under different thermo-mechanical treatments. Alloys were cast and subjected to standard sequential thermo-mechanical processes of rolling and age-hardening treatments. Average grain sizes were microscopically determined, and uniaxial tensile tests were performed to generate flow curves and evaluate yield strength of the alloys. Average grain diameter of 2219Al base alloy decreased (by 20.6%), while yield strength concomitantly increased (by 24.5%), with increasing Cd addition up to 0.061 wt%. Rolled peak-aged alloys recorded highest average grain refinement and increase in yield strength by 13.7% and 21.1% respectively, among all thermo-mechanical treatments. Effect of grain size on mechanical strength was analytically modeled through Hall–Petch equation, using Weighted Least Square methodology. Hall–Petch parameters of the alloys were evaluated for the first time, considering separate processing conditions. Yield strength values computed from Hall–Petch models, were successfully compared with experimental results with fairly good accuracy, to validate estimated Hall–Petch parameters. Hollomon equation was further used to mathematically model the flow curves. Strength coefficient (K) and strain hardening exponent (n) values were evaluated, first time for the present alloys, under different processing conditions. Trace contents of Cd and processing parameters exhibited to have significant potential to refine grain structure and enhance mechanical strength of 2219Al alloy. Present investigation provides a structure–property correlation to validate the manufacturing feasibility and prospective applications of these alloys, subjected under different thermo-mechanical treatments.