Influence of Feeding Techniques in Bottom Tapping Stir Casting Process for Fabrication of Alumina Nano-filler-reinforced Aluminium Composites

Abstract

Stir casting process is a prominent technique for the fabrication of aluminium matrix composites (AlMMCs). Regular feeding, two-step feeding, capsulate feeding, pre-melt feeding and double-layer feeding are different feeding methods used in stir casting technique. In this study, Al7075-MMCs reinforced with nano-sized Al2O3 are manufactured through five different feeding methods. The bonding between the matrix and ceramic interface, agglomeration of the particles and porosity are evaluated through scanning electron microscope. From the micro-structural characterization results, it is observed that double-layer feeding method ensures the better particle distribution and improved bonding between the Al7075 and Al2O3. Alumina particles of 50 nm size, 2.5 wt% are incorporated to the Al7075 matrix. The intensive porosity and high agglomeration are noticed in other methods. It is understood from the results that double-layer feeding technique is a promising route for producing the defect-free Al7075-MMCs. The density, micro-hardness, and tensile strength of the resultant composites are measured according to ASTM standards. Due to homogenous particle distribution, the ultimate tensile strength is increased from 280 to 387 MPa, which is 38% higher than Al7075. The yield strength of the composite is increased from 140 to 198 MPa. The micro-hardness is increased from 661 to 878 MPa.