Multi-Objective Optimization of Cold-Rolled Al-Li Alloy Produced via Powder Metallurgy Using Taguchi-Based Grey Relational Analysis

Enhancing the mechanical properties of powder metallurgy (PM) materials involves optimizing the PM specific process parameters, particularly in the design and manufacturing phases. To achieve high strength of PM materials, the fine-tuning of numerous process parameters is essential. Al-Li is an alloy known for its low density and high strength and is widely utilized in aerospace for creating various components. This study explores the mechanical properties of PM Al-Li alloys with microstructural analysis performed via SEM and XRD. Through Taguchi-grey relational analysis (GRA), multi-objective optimization of densification and mechanical characteristics is performed to obtain optimal processing conditions. Taguchi-GRA is a more efficient, robust, and practical optimization and design of experiment method for multi-objective problems, especially when resources are limited, or explicit models are difficult to derive. The sintering time, weight percentage of lithium, number of roll passes, and rolling orientation were parameters subject to optimization. Different compositions of Al-xLi (x = 0, 1, and 2 wt.%) are explored, alongside sintering durations of 60 and 120 minutes, followed by rolling operations with 2, 4, and 6 roll passes, and tensile testing at 0, 45, and 90 degrees to the rolling direction. The Taguchi-GRA was further integrated with entropy weight method to improve weights in the GRA criteria to enhance optimization to determine the optimal parameter combination as Al-2wt.%Li, 120 minutes sintering, 2 roll passes, and 90 degrees rolling direction. At these optimal parameter settings, the relative density, elastic modulus, yield strength, and ultimate tensile strength were 99.5%, 42881.034 MPa, 76.591 MPa, and 189 MPa, respectively.