Shaping porous, low density al composites by AWJ cutting process

Abstract

Abstract: Shaping materials containing porous constituents is a critical issue. This work analyses the process of abrasive water-jet (AWJ) cutting applied to low density metal matrix composites (LD.MMCs) consisting of AA7075 alloy as matrix and porous, foamed particles of SiO2/Al2O3/Fe2O3 or vermicular SiO2/Al2O3/MgO, as reinforcements. Results show that although presenting lower density (from 1.09 g/cm3 to 1.59 g/cm3, depending on the particle type) and lower strength than the non-reinforced AA7075 alloy, the composites present some difficulties in AWJ cutting. Deflection of the jet was noticed, being more evident on vermiculite-reinforced samples. Anyhow machinability numbers for the composites analyzed are in the order of 20% higher than the AA7075 matrix alone. Jet deflection, surface quality and machinability number showed to be dependent on the internal structure of the porous ceramic particles: vermiculite can pull out under the jet while cinasite is more susceptible to suffer fracture. This mechanisms result in lower jet deflection, better surface and better overall machinability in the case of AA7075 / cinasite LD.MMC