Microstructural evolution and enhanced performance of B4C-reinforced Al-5Mg alloy via wire arc additive manufacturing: Mechanical properties and wear mechanisms

• Optimum addition of B 4 C particles in WAAM Al-5Mg alloy interlayer is achieved. • 0.4 wt% B 4 C enhances alloy strength by 7.1% and wear resistance by 57.4%. • Dominant mechanism transits from adhesive wear to abrasive wear as B 4 C addition. • Grain refinement, mechanical strengthening, and wear resistance is correlated. In the field of wire arc additive manufacturing (WAAM), Al-5Mg alloys are widely used in the aerospace and automotive industries for fabricating structural components because of their low density, good corrosion resistance, and excellent weldability. However, as non-heat-treatable alloys strengthened primarily by solid-solution mechanisms, their mechanical properties are inherently limited. In addition, as-built WAAM components often exhibit low hardness and poor wear resistance, which significantly restrict their broader industrial application. To address these limitations, this study investigates the effect of interlayer B 4 C particle addition (0.2–0.6 wt%) on the microstructure, mechanical properties, and tribological performance of WAAM-fabricated Al-5Mg alloy. The results show that the addition of 0.4 wt% B 4 C reduces the average grain size by 52.8%, increases the ultimate tensile strength by 7.1% to 300 MPa, and enhances the hardness by 20.4% to 101.44 HV. Owing to the load-bearing effect of the hard B 4 C particles during sliding, the friction coefficient and wear rate decrease to 0.4406 and 7.1 × 10⁻³ mm³/(N·m), corresponding to reductions of 20.2% and 57.4%, respectively. When the B 4 C content reaches 0.6 wt%, particle agglomeration occurs, leading to deterioration of both mechanical and tribological properties. This study establishes a direct correlation among grain refinement, mechanical strengthening, and improved wear resistance, demonstrating the feasibility of B 4 C reinforcement for enhancing the comprehensive performance of WAAM-processed Al-5Mg alloys.