EFFECT OF La₂O₃ ADDITION ON MICROSTRUCTURE AND WEAR PROPERTIES OF CU-BASED METAL MATRIX POWDER COMPOSITES

Abstract

1 INTRODUCTION Copper-based MMCs are widely used in applications requiring high thermal and electrical conductivity, such as electrical contacts, heat exchangers, and brake pads. However, their relatively low hardness and poor wear resistance limit their tribological applications. To address this, reinforcement with ceramic oxides (e.g., Al₂O₃, SiC, La₂O₃) is a common approach. Rare earth oxides, particularly lanthanum oxide (La₂O₃), have garnered attention due to their ability to enhance grain refinement, dispersion strengthening, and tribological properties. La₂O₃ is thermally stable and enhances the interfacial bonding between the matrix and reinforcement particles. La₂O₃ particles act as nucleation sites during sintering, impeding grain growth and resulting in a fine-grained structure (Wang et al., 2018). With proper mixing and compaction, La₂O₃ disperses homogeneously, preventing agglomeration and promoting uniform microstructure (Liu et al., 2016). La₂O₃ enhances sintering densification, reducing porosity and thereby contributing to improved mechanical and wear properties. Increased Hardness: The hard La₂O₃ particles serve as a load-bearing phase, thereby improving the overall hardness of the composite (Chen et al., 2019). Reduced Wear Rate: La₂O₃ particles contribute to reduced material loss under sliding wear due to their ability to impede plastic deformation and minimize adhesive wear (Zhang et al., 2020). Improved Oxidation Resistance: At elevated temperatures, La₂O₃ forms a protective oxide film on the wear surface, which reduces oxidative wear. Most studies suggest that 1–3 wt.% La₂O₃ addition offers optimal results. Excessive La₂O₃ (>4 wt.%) may cause clustering, leading to poor dispersion and decreased mechanical performance (Huang et al., 2021).