Enhancement of Tensile Properties of AZ91–Ca–Sb Magnesium Alloy with SiC Nanoparticles Additions

Abstract

The present work investigates the effect of SiC nanoparticles (SiCnp) additions on the tensile properties of the squeeze-cast AZ91 + 2.0Ca + 0.3Sb (wt%) alloy at ambient, 423 K and 473 K temperatures. All the AZ91 + 2.0Ca + 0.3Sb + xSiCnp [x = 0.5 wt% (0.29 vol%), 1.0 wt% (0.58 vol%), and 2.0 wt% (1.16 vol%)] nanocomposites illustrate greater yield strength and ultimate tensile strength in contrast to the AZ91 + 2.0Ca + 0.3Sb alloy at all the temperatures employed. The yield strength, ultimate tensile strength and elastic modulus of both the alloy and the nanocomposites decline as the temperature increases, whereas the work to fracture increases with a rise in temperature. Among the nanocomposites, the one comprising of 2.0SiCnp demonstrates the best tensile properties. All the nanocomposites display superior strain hardening response than the alloy, and the maximum strain hardening is perceived in the AZ91 + 2.0Ca + 0.3Sb + 2.0SiCnp nanocomposite. The improved tensile properties of the nanocomposites are ascribed to the reduced grain size, the increase in dislocation density owing to Coefficient of Thermal Expansion (CTE) mismatch between the alloy and the SiC nanoparticles, the Orowan strengthening as well as the presence of a relatively higher amount of Al2Ca phase in the nanocomposites. The contribution to the improvement of strength of the nanocomposites in decreasing order of their influence are the strengthening due to CTE mismatch, the Hall–Petch strengthening, and Orowan strengthening. The fracture surfaces of the tensile specimens tested at 298 K confirmed the presence of transgranular cleavage fracture which remained unchanged at 473 K as well.