Microstructure and Tribological Property Correlations of Die Cast and Spray Formed Al-30 wt.% Si Alloy

Abstract

Al-30 wt.% Si hypereutectic alloy was produced by die casting and spray forming technique. The microstructures, mechanical and tribological properties of the alloy were studied. The density of die cast and spray formed samples are measured using water displacement method by applying the Archimedes principle. The scanning electron micrographs of die cast and spray formed alloys revealed the morphological changes of silicon phase from coarse silicon needles to fine silicon needles due to high undercooling encountered in spray forming. The size of the hard silicon platelets are decreased from 22 µm to less than 10 µm as the processing method is changed from die casing to spray forming. The average Vickers micro hardness of die cast and spray formed alloy are 70.06±2.65 HV and 78.05±2.01 HV respectively. The respective yield strengths of die cast and spray formed alloy are 130±9MPa and 150 ±7 MPa and the compression strengths are 251±11.6 MPa and 283±6.32 MPa. The precipitation strengthening mechanism is found to be involved in spray formed alloy.