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<p>In the microstructure of extruded ultrahigh-strength aluminum-based composites (AMCs), the distribution of SiC particles (SiC<sub>p</sub>) and the morphology of ultrafine grains (UFG) and coarse grains (CG) within the bimodal grain structure exhibit significant differences in the transverse (TD) and extrusion direction (ED). By adjusting the Mg content in the matrix, the ratio and distribution of UFG and CG were controlled, and the impact of this microstructural modification on friction and wear evolution was investigated. As Mg content increases, the hardness of the composite rises in both the TD and ED regions, while the hardness of the CG also increases, with the difference between the two gradually widening. The wear scar morphology in both TD and ED regions primarily exhibits characteristics of adhesive wear with oxidation. Initial friction-induced wear begins with plow-type wear, causing a sharp drop in the coefficient of friction. Subsequently, SiC<sub>p</sub> refine the wear debris and promote oxidation reactions, ultimately forming an oxide layer. During frictional wear, the oxide layer undergoes a “formation–exfoliation–reformation” cycle, maintaining a relatively stable coefficient of friction throughout. Due to the linear distribution of SiC<sub>p</sub> in the ED and the buffering effect of the CG, SiC<sub>p</sub> maintain prolonged contact with the grinding ball, resulting in superior wear resistance in the ED compared to the TD. Additionally, the wear rate increases with rising magnesium content. The 2.5&#xa0;Mg sample exhibited the lowest wear rates in the ED and TD, at 3.889 × 10<sup>−8</sup>&#xa0;mm<sup>3</sup>/N&#xa0;m and 4.237 × 10<sup>−8</sup>&#xa0;mm<sup>3</sup>/N&#xa0;m, respectively.</p>

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Effect of Linear Distribution of Composite Particles with Bimodal Grain Structure on the Friction Properties of Ultrahigh-Strength Aluminum Matrix Composites

  • 期刊论文

  • 发表日期：

    2025年12月26日

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  • Tian Han

摘要

In the microstructure of extruded ultrahigh-strength aluminum-based composites (AMCs), the distribution of SiC particles (SiCp) and the morphology of ultrafine grains (UFG) and coarse grains (CG) within the bimodal grain structure exhibit significant differences in the transverse (TD) and extrusion direction (ED). By adjusting the Mg content in the matrix, the ratio and distribution of UFG and CG were controlled, and the impact of this microstructural modification on friction and wear evolution was investigated. As Mg content increases, the hardness of the composite rises in both the TD and ED regions, while the hardness of the CG also increases, with the difference between the two gradually widening. The wear scar morphology in both TD and ED regions primarily exhibits characteristics of adhesive wear with oxidation. Initial friction-induced wear begins with plow-type wear, causing a sharp drop in the coefficient of friction. Subsequently, SiCp refine the wear debris and promote oxidation reactions, ultimately forming an oxide layer. During frictional wear, the oxide layer undergoes a “formation–exfoliation–reformation” cycle, maintaining a relatively stable coefficient of friction throughout. Due to the linear distribution of SiCp in the ED and the buffering effect of the CG, SiCp maintain prolonged contact with the grinding ball, resulting in superior wear resistance in the ED compared to the TD. Additionally, the wear rate increases with rising magnesium content. The 2.5 Mg sample exhibited the lowest wear rates in the ED and TD, at 3.889 × 10−8 mm3/N m and 4.237 × 10−8 mm3/N m, respectively.