Evaluation of Mechanical and Tribological Properties of Directionally Solidified Al-Si Based FG Composite

摘要

The present work aims to fabricate graphite reinforced Aluminum-Silicon (Al-Si) based functionally graded composite (FGC). The FGC's are obtained with the novel directional solidification technique under the influence of lateral vibrations. The accomplished cast composites are investigated for mechanical and tribological properties to understand the significance of vibrations. To validate the gradation in the structure, the FGC's have been analyzed for hardness at the top and bottom portion. Results revealed that top portion exhibited high hardness with 66 BHN compared to the bottom portion with 48 BHN respectively. These observations were also supported by the scanning electron microscope (SEM) morphologies which revealed that concentration of Si was more at the top portion. The spatial transition of Si can be attributed to the presence of the chill at the bottom and to the influence of lateral vibrations which has led to variation of properties within the structure. Ultimate tensile strength (UTS) results also showed shift in the properties with the bottom portion exhibiting 143.23 MPa compared to the top portion with 98.3 MPa. Furthermore, wear analysis carried out at the top and the bottom portion of the FGC showed that there is a decrease in wear loss, coefficient of friction and specific wear rate at the top portion compared to the bottom portion. Worn-out surface analysis revealed that graphite addition had imparted the self-lubricating property at the top portion which could serve as anti-friction and anti-wear applications in the automotive sector