Microstructural evolution and mechanical behavior of Al-Cu-Mg alloy with Li and graphite additions processed via high-energy ball milling and consolidated by high induction sintering

The present work investigates the microstructural evolution and mechanical behavior of Al–Cu–Mg alloys with lithium and graphite additions, processed via high-energy ball milling and consolidated using two different routes: conventional and high-frequency induction sintering. Samples were milled for 4 and 8 hours, with Li additions (0, 1, and 2 at. %) and a constant Gr addition (2 at. %) for the composites. The study evaluates the influence of composition, milling time, and sintering technique on the phase formation, thermal stability, microstructure and mechanical performance. Characterization was conducted through scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, microhardness testing, density measurement and compression testing. Evidence demonstrates demonstrate that high-energy ball milling successfully refines the microstructure and promotes a solid-solution formation, while high-frequency induction sintering enhances densification, reducing both porosity and oxidation and better retains the crystallite refinement obtained during the milling process. Thermal analysis characterization revealed relaxation and phase transformation behavior associated with the AlLi and Al₂Cu phases formation, as well as the effect of Gr on thermal stability. The presence of Li significantly increased oxidation and porosity, negatively affecting the mechanical properties at high concentrations. Conversely, Gr positively contributed positively as a process control agent and reinforcement agent. Among all studied conditions, the 4 h milled samples consolidated by high-frequency induction sintering presented the most balanced combination of strength, density, and structural refinement. These findings provide valuable insights into the design and processing of lightweight, high-performance aluminum-based composites.