Scatter and statistical analysis of tensile properties of cast SiC reinforced A359 alloys

The influences of foundry, composite ingot supplier, testing laboratory, volume (%) SiCp, mold type (sand or permanent), and surface finish (machining or non-machining), on the tensile properties of cast SiCp reinforced Al-matrix composites were studied. It is felt that through the numerical determination of effects of these variables, understanding of the scatter in properties will be enhanced and reproducibility of the composite tensile properties can be improved. Three different Al-SiCp composite ingots, including F3S.20S, F3S.30S, and Lanxide 4040-30P, were cast at two independent foundries, and they were heat-treated to T6 temper condition at one location. The tensile tests were performed at three different industrial laboratories. Some specimens were machined to observe the effect of surface finish (machining). Variations in tensile properties of bars cast under the same conditions using same raw material, at the same foundry have also been examined. The foundry and the testing laboratories were found to have significant influence on tensile properties. It was found that the modulus of the composite with 30 vol.% SiC (F3S.30S) was higher than that of the composite with 20 vol.% SiC (F3S-20S). However, the tensile strength of the composite containing 30 vol.% SiC (F3S.30S) was found to be lower than that containing 20 vol.% SiC (F3S-20S). Effects of variables, including foundry, composite ingot supplier, testing laboratory, and vol.% SiCp, were determined by using generalized linear model (GLM) analysis subroutine in commercially available software SYSTAT. The analysis was made to determine the significance and percent contribution of each of these factors on the tensile strength. The interaction between the influences of these factors was also examined. Results obtained indicate that there was no interaction between these variables to significantly influence the tensile properties.