Micro-indentation analysis of aluminium alloys: simultaneous evaluation of tensile properties and hardness characterisation via Knoop indentation

Nondestructive evaluation of mechanical properties and hardness for aluminum alloys is essential for ensuring structural integrity during service. This study establishes a quantitative relationship between the loading coefficient, unloading work, and elastoplastic constitutive behavior of aluminum alloys using Knoop micro-indentation data and dimensional analysis. Systematic calibration via finite element analysis (FEA) yielded a mechanical model defined by only eight parameters, enabling simultaneous determination of tensile stress-strain behavior, Knoop hardness (HK), and ultimate tensile strength from indentation measurements. Validation included forward/inverse analyses of 40 simulated scenarios and experimental tests on four aluminum alloys (6061-T651, 7075-T651, 2024-T4, 5052-H32). Results showed strong agreement between predictions and experimental data, with maximum relative deviations below 2% for HK and under 10% for tensile strength. The model provides an accurate, efficient nondestructive method for assessing aluminum alloy properties, supporting in-service structural evaluation.