Integrated RSM and micromechanical RVE–FEA approach for optimizing indentation behavior of HEA-reinforced AA7075 alloy fabricated via friction stir processing

In the present investigation, the response surface methodology (RSM), namely, the Box–Behnken design in conjunction with finite element analysis (FEA) was utilized to optimize the microindentation response of AA7075 alloy matrix reinforced by AlCoCrFeNiMn high-entropy alloy (HEA) particulates fabricated by the method of friction stir processing (FSP). The main response variables include Meyer’s hardness, R 1, crater diameter, R 2, crater depth, R 3, and lip height, R 4. The experimental factors are the size of reinforcement particles (20–60 μm), the weight fraction of reinforcement (3–9 wt%), and the applied load (10–100 N). Scanning electron microscopy coupled with energy checked X-ray spectroscopy (SEM/EDS) has verified a uniform and tightly spread distribution of HEA in the matrix of AA7075. The RSM modeling provided very significant quadratic relations (adjusted R 2 ≥ 0.987) from which the effects of each factor can be inferred. Analysis of variance shows that the applied load is the only factor that has a dominant influence on the modulation of all the indentations dimensions, whereas increases of the weight fraction of reinforcement and decreases in the particle size significantly improve Meyer’s hardness by increasing the interfacial constraint. Parallel to the experiment, 17 FEA models in Abaqus were built in order to clarify the pathways of micromechanical deformation. Through a joint optimization, the optimal parameter set can be found as the smallest particle size (20 µm), highest reinforcement fraction (9 wt%), and an intermediate load (35.777 N), which provides the highest overall desirability (0.502). The simulations, which are supported by representative volume element–finite element (RVE–FEA) analyses, show that this configuration dampens lip height by throttling material pileup to augment surface integrity. The FEA results of the selected conditions show excellent agreement with the experimental results, such as the Meyer’s hardness of 12,581.86 MPa is in good agreement with the measured value of 12,550 MPa, with a deviation of less than 0.3 %. These results highlight the effectiveness of an integrated methodological framework for customizing the indentation behavior of HEA reinforced aluminum composites for high demanding surface level applications.