Effect of reinforcement volume fraction and T6 heat treatment on microstructure, thermal and mechanical properties of mesophase pitch-based carbon fiber reinforced aluminum matrix composites

Abstract

To meet the requirements of structural and functional integration, machinability and workability of engineering materials, continuous mesophase pitch-based carbon fiber (MPCF) reinforced 2024 aluminum (Al) matrix composites with 20–50 vol % MPCF were fabricated by vacuum hot pressing method. The effects of MPCF volume fraction and T6 heat treatment on microstructure, thermal and mechanical properties of MPCF/2024Al composites were investigated. The results show that the interface of the as-sintered composite was well bonded. After T6 heat treatment, the amorphous layer at the interface changed from continuous to discontinuous and the interfacial bonding was further improved, but there was no interfacial reaction. The increase of MPCF volume fraction was beneficial to improve the thermal conductivity (TC) and elastic modulus (E) of the as-sintered composites, up to 258.3 W/(m⋅K) and 343.5 GPa respectively, while the composites with 30 vol % and 40 vol % MPCF respectively had the highest ultimate tensile strength (UTS) and a coefficient of thermal expansion (CTE) close to zero. After heat treatment, the TC and E were slightly changed, while the CTE was further reduced and UTS was significantly improved. In this work, the heat-treated composite with 30 vol % MPCF had the highest UTS of 499.3 MPa and good thermal properties, and the TC of this composite may be further improved by using MPCFs with higher TC. Therefore, this composite is expected to become a promising engineering material integrating structure and function.