Stress-rupture measurements of cast magnesium strengthened by in-situ production of ceramic particles

We have introduced a polymer precursor into molten magnesium and then in-situ pyrolyzed to produce castings of metal matrix composites (P-MMCs) containing silicon-carbonitride (SiCNO) ceramic particles. Stress-rupture measurements of as-cast P-MMCs was performed at 350 °C (0.69TM) to 450 °C (0.78TM) under dead load condition corresponding to tensile stress of 2.5 MPa to 20 MPa. The time-to-fracture data were analyzed using the classical Monkman-Grant equation. The time-to-fracture is thermally activated and follows a power-law stress exponent exhibiting dislocation creep. Fractography analysis revealed that while pure magnesium appears to fracture by dislocation slip, the P-MMCs fail from the nucleation and growth of voids at the grain boundaries.