Thermal fatigue crack propagation mechanism of SiCp/A356 composites for urban rail train brake disc

Abstract

In order to study the influence of the service temperature load and material microstructure on the thermal fatigue crack growth behavior of SiCp/A356 composites, and to clarify the microscopic mechanism of thermal fatigue crack growth, the thermal fatigue crack growth test of SiCp/A356 composites was carried out. The results show that the crack growth process includes the slow growth stage caused by the deflection of SiC particles and the release of the driving force of the secondary crack growth, and the rapid growth stage where the main crack is connected with the micro-damage front end of the crack growth. When the heating temperature is low, the "step-like" feature of crack growth is obvious, the overall growth rate is slower, and the crack width is smaller, the crack propagation methods are particle fracture, light-mass matrix tearing and cracking along the interface. When the heating temperature is higher, the "oblique straight-line jump" stage is more obvious, the crack width is large and the growth rate is high, the crack growth is dominated by particle shedding and large-scale matrix tearing. Main crack always propagates forward with less resistance by choosing to follow the SiC particle group or directly pass through the α-Al matrix, when Si phase is loaded, it is easy to fracture and become the source of crack propagation. At the same time, the micro-damage at the front end of the crack propagation has a guiding effect on the crack propagation.

Keywords

• sicp/a356 composite
• service temperature load
• thermal fatigue
• microscopic mechanism of crack propagation