Enhancement of mechanical properties in LM13 aluminum alloy using hybrid ZrB 2 and B 4 C reinforcements via stir casting

In the present study, the mechanical behavior of LM13 aluminum alloy-based hybrid composites reinforced with zirconium diboride and boron carbide particles synthesized by the stir casting process was investigated. The objective was to tailor the mechanical properties of the alloy by changing the total amount of reinforcement up to 10 wt.%. Five different compositions were produced, including unreinforced LM13 and the hybrids with a gradually increasing level of the reinforcements, which were afterwards tested by hardness, tensile, and impact testing, as well as microstructural characterization. With ceramic reinforcements, strength and hardness increased significantly. Hardness increased from 72 Hv to 97 Hv, ultimate tensile strength 19.2%, and yield strength 24.3%. Due to homogeneous reinforcement distribution and excellent interfacial bonding, as revealed by microstructural analysis, enhanced grain refinement, load transfer, and Orowan strengthening resulted in improved properties. On the other hand, a decline in the ductility and impact resistance was noticed: elongation dropped from 5.7% to 4.0%, and impact strength decreased by 29.9% in a typical strength-toughness tradeoff of composites. The uniform distribution of reinforcements and low porosity with a maximum value of 5.55% percentage identified in the microstructural evaluations corroborated the reliability of the stir casting process.