Effect of TiB2 on the wear resistance of cast Al-Zn-Mg-Cu alloys

• Increasing TiB 2 content promoting the formation of a “lattice-like” network structure of AlZnMgCuB alloy. • TiB 2 promoted the transformation of the coarse, elongated fibrous grains of the as-cast Al Alloy to fine and equiaxed grains. • TiB 2 particles serve as effective nucleation sites for α-Al grains, inducing heterogeneous nucleation and grain refinement. • TiB 2 particles enhanced the hardness of the as-cast Al Alloy, significantly improving its wear resistance. • Explanation of the influence of the optimized TiB 2 content on the mechanism for effectively transferring and distributing the applied load. The influence of TiB 2 on the microstructure, hardness, and wear resistance of Al-Zn-Mg-Cu/TiB 2 composites was systematically investigated in this study. Multi-scale characterization techniques were used to analyze the distribution of TiB 2 particles, their interfacial structure, and their interactions with precipitates. The results indicated that the incorporation of an appropriate amount of TiB 2 particles significantly refined the resulting grain structure. The agglomerated TiB 2 particles formed a distinctive network-like architecture, which effectively transferred and dispersed applied loads, leading to a multi-scale synergistic strengthening effect. A composite with 2.5 wt.% TiB 2 exhibited approximately 17.2% and 31.2% improvements in modulus and hardness, respectively, compared to a reference Al-Zn-Mg-Cu alloy. A composite with 4 wt.% TiB 2 demonstrated optimal wear resistance, with a wear reduction of about 47.3% relative to the Al-Zn-Mg-Cu alloy. It was found that the dominant wear mechanism transitioned from a mixed wear mode to mild adhesive and abrasive wear. From the perspectives of microstructure and crystallography, this work elucidated the synergistic mechanism by which TiB 2 content influenced the strengthening and wear behavior of aluminum composites, providing a theoretical foundation for the design and fabrication of high-performance wear-resistant aluminum matrix composites.