Evaluation of microstructural and mechanical properties of A356 composite strengthened by nanocrystalline V8C7-Al2O3 particles synthesized through mechanically activated sintering

Abstract

In the present study, nanocrystalline V8C7-Al2O3 particles were successfully synthesized through mechanical activation sintering method, followed by investigating the feasibility of adding of particles produced as reinforcement for achieving a uniform distribution of V8C7-Al2O3 particles into A356 matrix. The primary materials including, V2O5, Al, and carbon black were powdered under different milling times. The X-ray diffraction (XRD) patterns showed that V8C7-Al2O3 was obtained after heat treatment of 12 h milled powders at 800 °C in the microwave. The nanocomposite A356-V8C7-Al2O3 with three different reinforcement weight percentages (1, 2, and 3 wt%) was fabricated by the stir-casting process. The results showed that milling of powders leads to an increase in the amorphous phase percentage with the time of mechanical alloying and results in a decline of crystallite phase percentage. The results of XRD analysis indicated that the synthesized V8C7 has nanometric particles and a deviation of lattice parameter from the standard state. Based on these results, microstructural examinations of the nanocomposites by Scanning Electron Microscope (SEM) showed uniform distribution, grain refinement, and porosity in the prepared specimens. Also, energy dispersive spectroscopy (EDS) analysis of nanocomposite strengthened with 2 wt% V8C7-Al2O3 demonstrated the percentage of nanoparticles needed for reinforcement alongside the silicon eutectic. Furthermore, the amount of porosity in the composites increased with increasing weight percentage while increasing the V8C7-Al2O3 reinforcement led to the improvement in yield strength, ultimate tensile strength, compression strength, and hardness.