Deformation mechanisms and texture evolution of in-situ magnesium matrix composites containing polymer derived SiCNO dispersoids during hot compression

In-situ magnesium matrix composite was fabricated by injecting a liquid polymer directly into, and having it converted into 2.5 vol% SiCNO ceramic dispersoids, within molten Mg using a stir-casting method. The deformation mechanisms and texture evolution for these as-cast composites were investigated in a strain rate range of 10−3− 1 s−1 within a temperature range of 150-350 °C under uniaxial compression. It was observed that the deformed composites follow a power-law creep having a stress exponent, n = 8 and activation energy, Q = 149 kJ mol−1 which suggest that deformation mechanism is controlled by lattice self-diffusion for constant structure creep. It was found that in the range of 150-250 °C, with a ratio of rate of work-softening to rate of work-hardening of about 0.80, twinning induced shear bands nucleate and propagate along the direction of maximum shear stress. When the temperature approaches 350 °C, the plastic flow is dominated by dislocation assisted slip. Analysis of Zener-Hollomon parameter (Z) revealed that the transition from twinning into dislocation slip dominated deformation progresses at 1013 s−1 < Z < 1015 s−1. Macro-textural studies confirm that while basal plane assists deformation by twinning mechanism, the non-basal prismatic planes favor significant plastic deformation by dislocation assisted slip for the in-situ composites.