Analysis of microstructural, mechanical and thermal behaviour of thixocast LM25-10wt SiC composite at different processing temperatures

摘要

In this study, composite was made by the addition of 10 wt SiC particles in the LM25 matrix through gravity casting and thixocasting processes. Thixocasting temperature was varied to investigate its effect on the microstructure, mechanical and thermal properties. Properties of thixocast samples were also compared with gravity cast ones. XRD analysis was done to analyse the phases present in the samples. Optical microscope and scanning electron microscope were used to record the microstructures of gravity cast as well as thixocast samples. Tensile, compressive and flexural tests were performed on universal testing machine with the prepared composite samples according to the ASTM standards. Thermal diffusivity tests of gravity cast and thixocast samples were done on laser flash diffusivity instrument. Results reveal that thixocast samples are sounder than the gravity cast samples. The microstructure of alpha-Al phase transformed from dendritic to globular shape due to the thixocasting. Also, volume fraction of eutectic phase in the sample increased with the increment of thixocast temperature. Tensile strength, compressive strength and flexural strength were found higher in the case of thixocast samples as compared to gravity cast. Thermal diffusivity considerably increased due to thixocasting, while its value slightly reduced with increment of thixocast temperature.