THE EFFECT OF ROLLING CONDITIONS ON THE PROPERTIES OF ALUMINUM POWDER COMPOSITES REINFORCED BY SiC, TiC, AND  AlB₁₂ NANOPARTICLES

Abstract

The effect of high-temperature deformation modes on the mechanical properties of composites produced from aluminum powders with varying particle-size distribution reinforced by SiC, TiC, and AlB₁₂ nanoparticles was examined. High-temperature extrusion promoted uniform distribution of the nanoparticles in the aluminum matrix. At an optimum nanoparticle content (4 wt.%), the most uniform distribution of particles following deformation processing was shown by the composites produced from a fine size fraction of the aluminum powder. Subsequent high-temperature rolling promoted significant strain hardening (up to 120 MPa) through thermokinetic deformation conditions favorable for the formation of dislocation substructures and activation of dynamic recrystallization processes. In all cases, the hardening rate at the initial stage of high-temperature rolling (first pass) was higher than at the subsequent stages when recovery processes activated. The abnormal decrease in strength of the samples subjected to asymmetric rolling to reach high strains was associated with intensification of shear deformation, increasing ribbon internal energy and thus accelerating the annealing of deformation defects. Among the nanopowder reinforcements, the best mechanical behavior was demonstrated by SiC nanoparticles, whose structural features promote the best contact between the particles and the matrix. The samples with AlB₁₂ nanoparticles showed lower hardening because of poorer contact and presence of process-induced particles. Titanium carbide nanoparticles provided the worst hardening of the composite because of insufficient bonding with the matrix. The tested deformation modes, along with the optimal choice of powder components for the composites, allow the production of high-strength ribbons (aluminum metal-matrix composites) employing a relatively simple powder technique. A further increase in ribbon strength should be promoted by the use of doped aluminum powders following upgrade of the deformation modes.