Friction anisotropy and microstructural evolution mechanism of a heterostructured Al₃BC/6061Al composite at room and elevated temperatures

The tribological behavior and microstructural evolution mechanism of a heterostructured Al₃BC/6061Al composite were systematically investigated during reciprocating sliding along parallel (ED) and perpendicular (TD) extrusion directions at temperatures ranging from 25 to 350 °C. The composite exhibits significant friction and wear anisotropy at different temperatures. At 25 °C, the coefficients of friction of the composite when sliding along the ED and TD were 0.901 and 0.686, respectively. When sliding at 350 °C, they changed to 0.792 (ED) and 0.861 (TD). The wear rates of the sample sliding along the ED at 25, 200, and 350 °C were 3.8×10⁻⁴, 3.7×10⁻⁴, and 4.3×10⁻⁴ mm³/(N·m), respectively, which were reduced by 16%, 27%, and 19% compared with those of the sample sliding along the TD. The dominant wear mechanism of the composite transformed from abrasion and delamination wear at 25 °C to oxidative and delamination wear at 350 °C. A gradient grain structure and an amorphous oxide phase were formed in the subsurface of the composite during sliding. The nanograins formed in the subsurface are beneficial to wear resistance at 25 °C. The growth of dynamically recrystallized grains and thickening of the amorphous oxide layer at 350 °C increased the wear rate of the composite. The higher wear rate of the samples sliding along the TD is attributed to more oxygen atom intrusion into the matrix, resulting in more dispersed cracks within the amorphous oxide phase. This work provides a theoretical basis for designing wear-resistant aluminum matrix composites by revealing the tribo-induced subsurface deformation mechanisms at different temperatures.