Study on the strength-plasticity enhancement mechanism of the SiCp/Fe symmetric gradient structure and alloying in the high-particle-content layer

Abstract

The construction of heterogeneous structures is an effective method to achieve a favorable balance between material strength and ductility. By controlling the silicon carbide (SiCp) particle content, Fe-based layered composites with a symmetric gradient structure were prepared using spark plasma sintering (SPS) and subjected to hot rolling to investigate the microstructural evolution and mechanical performance of each layer. The results show that the gradient distribution of SiCp content leads to different grain sizes across the layers. The formation of an amorphous layer between SiCp and Fe, as well as FeSiO₃ crystalline products, promoted strong bonding between the two. The gradient distribution of SiCp content resulted in a symmetric gradient in Vickers hardness values across the material. Compared with pure Fe, homogeneous 3 % SiCp/Fe, and 10 % SiCp/Fe composites, the SiCp/Fe symmetric gradient structure exhibited higher hardness without a significant reduction in plasticity. After hot rolling, the yield strength of the SiCp/Fe symmetric gradient structure reached 912.45 MPa, with an elongation of 7.67 %. In this study, the strength and plasticity of the symmetric gradient structure were enhanced by 178.10 % and 56.53 %, respectively, compared with the Fe-8Cr-4.5Ni structure prepared by SPS. This demonstrated the synergistic enhancement effect of the symmetric gradient design on strength and plasticity. Additionally, due to the high localized stresses during the hot rolling process, SiCp in the 10 % SiCp/Fe layer was decomposed and reacted with the Fe matrix to form Fe-C and Fe-Si compounds. The ultrafine grains in this layer also contributed to the high strength of material.