The compensation mechanism of thermal mismatch stress induced by submicron SiCp on the thermal cycling degradation of SiCp/Al-Si-Mg composites

The performance degradation of composites caused by thermal cycling during braking is the main bottleneck limiting the application of aluminum-based composites in brake materials. In this study, a strategy of dual-scale SiCp design is proposed: submicron SiCp are introduced to induce higher thermal mismatch stress that compensates for the decrease in hardness and wear resistance caused by long-term thermal cycles, and the performance degradation under thermal cycles was effectively addressed which demonstrates considerable application potential for brake materials in service at temperatures below 300 °C. A recrystallization model of composites with sub-micron SiCp is proposed according to particle stimulated nucleation of recrystallizations. Sub-micron SiCp provide higher thermal mismatch stress, driving the occurrence of recrystallization, while the substructure evolution of composites without sub-micron SiCp is mainly due to recovery. The addition of 1 wt% sub-micron SiCp also synchronously increase the elongation, tensile strength, yield strength and hardness by 29.8%, 15.3%, 20.3% and 12.5%. The main strengthening mechanism can be attributed to the noticeable coefficient of thermal expansion mismatch strengthening provided by sub-micron SiCp.