Microstructural Evolution and Simultaneous Enhancement of Mechanical and Tribological Properties in Low‐Mass‐Fraction B 4 C/7075 Al Composites

Low‐mass‐fraction B 4 C/7075 Al composites were fabricated via ball milling combined with vacuum hot‐press sintering. The effects of B 4 C content on the microstructure, density, mechanical, and tribological properties of the composites were systematically investigated. The results show that the ultimate tensile strength (UTS), yield strength (YS), elongation (EL), and hardness initially increase and subsequently decrease with increasing B 4 C content. In contrast, the porosity, wear rate, coefficient of friction (COF), and worn surface roughness present an opposite variation trend. The composite with 2 wt% B 4 C achieves the optimal comprehensive mechanical properties (UTS: 289 MPa, YS: 184 MPa, EL: 15.4%, hardness: 109 HV). The uniform dispersion of B 4 C particles, the precipitation of Mg(Zn, Cu) 2 phase, and excellent interfacial bonding between B 4 C and Al matrix are responsible for the significant enhancement of mechanical properties, among which thermal mismatch strengthening is the dominant strengthening mechanism. Meanwhile, the 2 wt% B 4 C/7075 Al composite possesses superior tribological properties, with the minimum wear rate of 1.03 × 10 −9 mm 3 /(N·m), COF of 0.37, and worn surface roughness of 34.5 μm, representing reductions of 54.0%, 21.3%, and 47.4% compared with the matrix alloy, respectively. Furthermore, adhesive and abrasive wear act as the dominant wear mechanisms.