Effects of cryo-FSP on metallurgical and mechanical properties of stir cast Al7075–SiC nanocomposites

Abstract

The present research aims to develop high strength Al7075–SiC nanocomposites by integration of stir casting and cryo-FSP. Al7075 alloy based nanocomposites reinforced with varying wt.% (2%, 3% and 5%) of nanosize SiC particles were produced through the bottom pouring stir casting technique. The cryo-FSP was successfully carried out using optimized parameters (i.e. 1025 rpm and 65 mm/min traverse speed) on as-cast samples. To understand the fundamentals of the deformation characteristics and microstructural evolution, a systematic study on microstructural evolution has been performed by SEM with EBSD and TEM. The mechanical properties were evaluated by Vickers hardness and tensile testing. Improvement in the mechanical properties is found to be the maximum for the Al7075-3 wt% SiC nanocomposite sample obtained through cryo-FSP (TS = 552 MPa, and %El. = 17%) as compared to other samples studied (Al7075 alloy/composites). Secondary processing through cryo-FSP not only refined the matrix grain size to 1–3 μm range, but also suppressed the coarsening of the strengthening η′ phase due to higher cooling rate. Moreover, the reinforced nanosize SiC particles distributed uniformly within the matrix thereby enhancing the particle/matrix interface characteristics. These modifications in microstructure drastically enhance the strength (YS, hardness) and ductility of the material simultaneously. The detailed strengthening mechanisms have been analyzed and correlated with the mechanical properties.