Performance assessment of stir-cast B 4 C–ZrB 2 /AA2014 composites and their friction stir-welded joints for advanced engineering applications

This study investigates the microstructural changes and mechanical features of Aluminum Matrix Composites (AMCs) reinforced with Boron Carbide (B4C) and Zirconium Diboride (ZrB2), manufactured by Stir Casting method and subsequently joined via Friction Stir Welding (FSW). Hybrid composites with different reinforcement proportions were examined, and the composition comprising 5 wt% B4C and 15 wt% ZrB2 (S5) had the most beneficial features. The S5 composite attained a Ultimate tensile strength (UTS) of 254. 53 MPa and Vickers hardness of 149 HV, considerably above the base AA2014 alloy’s values of 176.66 MPa and 113 HV respectively. However, its ductility decreased, with elongation reducing from 3.98% for the base alloy to 3.17% for the S5 composite. The Specific Wear Rate (SWR) diminished by approximately 60% attributed to its improved load-bearing capacity of the ceramic reinforcements. FSW produced defect-free joints on both the base alloy and hybrid composite, distinguished by finely equiaxed grains in stir zone caused by dynamic recrystallization. The hardness distribution across the weldment exhibited consistently increased values for the hybrid composite, exhibiting a maximum hardness of 149 HV in the parent zone and 132 HV in the stir zone. The FSWed S5 composite exhibited enhanced yield and ultimate tensile strengths (113 MPa and 152 MPa, respectively) relative to the base alloy, along with a little decrease in elongation. The impact toughness improved from 8 to 10 J, and fractographic analysis demonstrated a mixed ductile – brittle fracture, emphasizing the function of ceramic particles in strengthening and crack initiation, thereby enabling these composites suitable for superior performance in aerospace and automotive applications.