Study of the micro-yielding behavior in a SiC_p/Mg-Zn-Ca composite using synchrotron radiation diffraction

The present study investigates the mechanical behavior of a SiCp/Mg-5Zn-0.2Ca composite under tensile loading using in-situ synchrotron X-ray diffraction. The composite exhibited a yield strength of 167 MPa, ultimate tensile strength of 276 MPa, and tensile elongation of 15%. It was found that the onset of micro-yielding at a stress level of approximately 40 MPa, which is attributed to the thermal and interfacial mismatches between the SiC particles and alpha-Mg matrix. Furthermore, load partitioning between the SiC particles and alpha-Mg grains was observed following the micro-yielding event, indicating micro-load transfer from the softer alpha-Mg grains to the SiC particles. The occurrence of microcracks at the SiC/Mg phase interfaces after the micro-yielding event may have implications for the composite's overall fracture behavior. These findings underscore the influence of interfacial thermal mismatch on promoting micro-yielding in the composite. Several factors including reducing forming temperatures, utilizing reinforcements with lower coefficients of thermal expansion, and adjusting the alloying elements can be used to mitigate such micro-yielding effect.