Effects of SiCp distribution on microstructure, mechanical properties and deformation behavior of SiCp/2024Al composites

SiCp/2024Al composite was prepared by semi-solid stirring casting, and the distribution of SiCp was regulated by multi-step deformation of hot extrusion and multi-direction forging (MDF). The effects of SiCp distribution on the microstructure and properties of SiCp/2024Al composite ware studied. The results show that hot extrusion deformation cause SiCp to distribute along the extrusion direction (ED). After multi-directional forging, SiCp distribution is improved significantly, and it changes from directional distribution to uniform distribution. After 1MDF, the SiCp distribution along the ED changes to disordered distribution, and the mechanical properties of the material are sharply decreased. After 3MDF, the distribution uniformity of SiCp is improved, and the mechanical properties of the material are greatly improved. When the forging passes increase to 6, the distribution uniformity of SiCp is further improved, the mechanical properties of the material decrease with the partial SiCp breaking. When the forging number is 3, the mechanical properties of the composite are optimal, with yield strength, ultimate tensile strength and elongation are 264 MPa, 387 MPa and 7%, respectively. Compared with the directionally distributed composite, the uniform distribution of SiCp effectively relieves the local stress concentration, and the matrix alloy stores more dislocation. In addition, when the distribution uniformity of SiCp is improved, the Al2Cu phase is also refined. The diffuse distribution of Al2Cu phase hinders the slip of dislocation, resulting in a uniformly distributed composite with a higher work hardening rate and internal stress. In order to study the effect of SiCp distribution on softening behavior of composites, cyclic stress relaxation experiments are carried out. In the process of stress cycling, the uniformly distributed SiCp/2024Al composites with uniform distribution of SiCp and Al2Cu phases exhibit a better stress relaxation resistance.