Microscratch characteristic and deformation mechanism of SiC particle-reinforced composites at elevated temperatures

The effect of temperature on scratching forces for 16% SiC/Al and 45% SiC/Al composites was investigated in this article. The results showed that the mean normal forces for 16% SiCp/Al and 45% SiCp/Al decreased by 80% and 68% at 300°C compared with 25°C, and the average tangential force decreased by 67% and 66%, respectively. The reason was that the strength of composites was reduced with the increasing temperature, which results in a reduction of flow stresses in the primary shear zones. There are three stages occurring in the scratching process according to the cutting tool interacting with different phases with the increasing temperature. The temperature and the particle contents have an obvious effect on the deformation mechanism by influencing the ratio value of the elastic modulus and hardness. It is founded that the friction coefficient increased fast when the temperatures increased from 25° to 300°C for both 16% SiCp/Al and 45% SiCp/Al composites, and the temperature provided a bigger influence compared with the particle contents. Furthermore, two distinct regions of the hardness variation with the increasing temperature for both two composites were observed: (1) a gradual decrease with the temperature up to 285°C and (2) an abrupt dropping above 285°C. Finally, a physical model representing the deformation process considering the elastic recovery and piles up in high temperature has been developed.