Predicted enhanced wear resistance and mechanical integrity in AA8011 composites via dual-ceramic ZrB2 and B4C reinforcement

The mechanical and dry-sliding wear characteristics of AA8011 aluminium matrix composites (AMCs) reinforced with 2, 4, 6 and 8 wt% zirconium diboride (ZrB₂) and boron carbide (B₄C) manufactured using the stir casting process at 760 °C and 380 rpm are explored. The microhardness, ultimate tensile strength (UTS), coefficient of friction (COF), and wear rate were systematically investigated as a function of reinforcement type, content and sliding distance. AAZ-8 composite showed that the microhardness was 93 HV, which is 34.78% higher than that of unreinforced AA8011 (69 HV), and ZrB₂ composite showed that its microhardness was 4.71–6.90% higher than AA8011/B₄C composite. The improvements in UTS were 42.2% and 45.5% for AAZ-8 and AA8011/8 wt% B₄C (AAB-8), respectively, when compared to AA8011 with UTS of 154 MPa. AA8011/8 wt% B₄C (AAB-8) resulted in 2.3–4.6% higher UTS than ZrB₂ at the same reinforcement concentration. The results of dry sliding tests with an EN31 steel counterface showed that the wear rate and COF decreased continuously as the reinforcement content increased and sliding distance carried out ranged from 600 m to 2400 m. The reasons for this improvement were attributed to improved load-bearing capacity, surface work hardening, debris redistribution and protective secondary tribological layers. The SEM analysis showed that the particles were evenly dispersed at 2 wt% reinforcement but, when the reinforcement level was increased to 8 wt%, particle clusters and local defects were observed. Worn surface analysis revealed an evolution from two-body abrasion to three-body abrasion, adhesive interaction, and mechanically mixed tribo-film formation with extended sliding. In general, ZrB₂ was mostly effective at increasing the hardness of the cemented materials, while B₄C was most effective at increasing tensile strength, indicating promising role of both reinforcements in engineering applications involving wear.