Strength-ductility trade-off via SiC nanoparticle dispersion in A356 aluminium matrix

A process was developed to disperse β-SiC nanoparticles (NPs), with a high propensity to agglomerate, within a matrix of A356 aluminum alloy. A suitable dispersion of 1 wt% SiC NPs in the A356 matrix was obtained through a hybrid process including a solid-state modification on the surface of the NPs, a two-step stirring process in the semi-solid and then the liquid-state, and a final hot-rolling process for fragmentation of the brittle eutectic silicon phase and porosity elimination. Titanium and nickel where used as the nanoparticle SiC surface modifiers. Both modifiers were found to improve the mechanical properties of the resulting material, however, the highest improvement was found from the nickel surface modification. For the nickel modification, compared to the non- reinforced rolled alloy, more than a 77%, 85%, and 70% increase in ultimate tensile strength (UTS), yield strength (YS), and strain % at the break, respectively were found with respect to the unreinforced rolled A356. For the rolled nanocomposite containing 1 wt % SiCnp and nickel modification, an average YS, UTS, and strain % at the break of 277 MPa, 380 MPa, and 16.4% were obtained, respectively, which are unique and considerable property improvements for A356 alloy