Process optimization of laser metal deposition for fabrication of AlCoCrFeNi_2.1 high-entropy alloy

This study investigates and optimizes the laser metal deposition (LMD) process for fabricating AlCoCrFeNi_2.1 high entropy alloy (HEA). An orthogonal experiment combined with response surface methodology (RSM) was employed to establish quantitative relationships between key process parameters and melt pool geometry. Results show that laser power (P) predominantly influences the Track width (W), while scanning speed (V) primarily affects the track height (H); both exhibit a coupling effect on the aspect ratio (λ). Regression analysis based on a central composite design (CCD) revealed that the W model achieved excellent fitting accuracy (R² = 0.9997), indicating a strong nonlinear dependence on P. The H model followed a linear trend (R² = 0.7285), whereas λ showed limited predictability. Multi-objective optimization identified the optimal parameters as P = 1100 W and V = 540 mm/min, achieving λ values within the desired range of 2.5-4. Samples produced under optimized conditions exhibited uniform microstructures with refined grains and no visible defects. Mechanical testing demonstrated superior performance, achieving a tensile strength of 877.4 ± 6.3 MPa and an elongation of 4.0 ± 0.18%, alongside uniformly distributed Vickers hardness. These results confirm the reliability of the RSM model and highlight the critical role of energy input in controlling solidification behavior and mechanical response. Overall, this work provides a validated optimization framework for LMD-processed HEAs, offering both theoretical insights and practical guidance for the additive manufacturing of high-performance metallic materials.