Optimization of volume fraction and microstructure evolution during thermal deformation of nano-SiCp/Al–7Si composites

Abstract

This paper takes nano-SiCp/Al–7Si matrix composites prepared by powder metallurgy as the research object. With the help of advanced microstructure characterization techniques and performance analysis methods, the effect of nano-SiCp volume fraction on the microstructure and properties of composites is systematically studied. Based on optimizing the volume fraction of nano-SiCp, the thermal deformation behavior of the composites is investigated. It was found that with an increase of nano-SiCp content, the distribution uniformity of nano-SiCp decreases gradually. And because the surface of nano-SiCp is easy to adsorb gas and the aggregated distribution of nano-SiCp is not conducive to the sintering process, the density of the composites shows a gradually decreasing trend. The hardness of the composites tends increasing gradually, and the increase in amplitude gradually decreases. Due to the addition of nano-SiCp, there are many interfaces between SiCp and Al matrix, and cracks are prone to initiation and expansion at the interface. Therefore, as the volume fraction of nano-SiCp increases, the elongation of nano-SiCp/Al–7Si composites gradually decreases. When the volume fraction of nano-SiCp is 2%, the strength of the composites reaches the maximum value of 217 MPa. Compared with the Al–Si alloy without adding nano-SiCp, the results increased by 37.3%. In addition, with the decrease of strain rate and the increase of deformation temperature, the dislocation density in the composites gradually decreases, and the dynamic softening progresses more fully. The dynamic recrystallization nucleation mechanism mainly includes the subcrystal merging mechanism and the grain boundary bowing mechanism.

Keywords

• nano-sicp/al–7si composites
• volume fraction
• microstructure
• performance