Effect of Ageing Temperature on the Hardness, Microstructural and Dry Sliding Wear Performance of the Functionally Graded A356 Alloy

The present investigation aims to fabricate functionally graded aluminium alloy A356 processed through stir casting followed by vertical centrifugal casting. The hardness was examined using a Vickers’s microhardness tester, and the microstructure was examined through an optical microscope (OM), high-resolution scanning electron microscope (HRSEM), and X-ray diffraction (XRD) instrument. The dry sliding wear behaviour was examined using a pin-on-disc tribometer to study the influence of ageing temperatures (145, 165, and 185 °C), various zones (outer, middle, and inner) and applied load (10, 20, and 30N) on the specific wear rate (SWR) and coefficient of friction (COF). The sample aged at 165 °C had a 50% higher maximum hardness in the higher hardness zone than the as-cast FG aluminium alloy. Taguchi's technique and analysis of variance (ANOVA) determined the best and most significant sliding wear variables. The lowest SWR and COF of 0.00100 mm³/Nm and 0.382 were identified at the 165 °C aged higher hardness zone with a load of 10 N, and ANOVA analysis revealed that the applied load had a major impact. The worn surface examination confirmed the minimal wear damages in the higher hardness zone with an abrasive wear mechanism. The wear debris examination confirmed the oxide layer formation due to the tribochemical reactions.