International Journal of Lightweight Materials and Manufacture (Sep 2023)
Impact of aging temperature on the metallurgical and dry sliding wear behaviour of LM25 / Al2O3 metal matrix composite for potential automotive application
Abstract
The current study exhibits the influence of aging temperatures on the metallurgical, hardness, and dry-sliding wear behaviour of LM25 (Al-6.6Si-0.2Mg) alloy reinforced with Al2O3 particles. The LM25 alloy reinforced with 10 wt% of alumina particles was fabricated using the liquid metallurgy route followed by solutionizing and aging. The baseline LM25 alloy and its composite were solutionized at 538 °C for 8 h and were aged at 155, 165, and 175 °C for 12 h. Optical, FESEM, EDS, and X-ray diffraction analysis were done on the fabricated alloy and its composite in all conditions. The microstructure revealed the formation of the Mg2Si phase in the baseline alloy and the MgAl2O4 spinel generated at the composite interface of the aluminium matrix. The heat-treated alloy and composites were tested for their hardness on the Vickers microhardness tester. It was concluded that the aging temperature of 155 °C displayed significant enhancement in hardness values for tested samples. The heat-treated alloy and composite samples displayed an increment of 96% and 55% in hardness values relative to LM25. The wear rate and friction coefficient for the fabricated samples were analyzed using the pin-on-disc tribometer under dry sliding conditions. The hardness value increased from the as-cast state to samples aged at 155 °C and then decreased at 165 and 175 °C. Based on the wear study, a 14% and 25% decrease in the wear rate values for heat-treated alloy and composites were noted when sliding velocity was increased from 1 m/s to 3 m/s. However, the coefficient of friction (COF) decreased by 23% and 13% for the specimens in the same conditions. Furthermore, a similar trend was displayed by age-hardened LM25 alloy and the composite when subjected to varying load (5, 10, 15 N) condition. Lastly, the worn-out surface mechanisms were examined using FESEM analysis. Amongst the investigated samples, LM25/10 wt% Al2O3 composite aged at 155 °C revealed the least wear rate when subjected to an external load of 5 N and sliding velocity of 2 m/s. Therefore, it can be suggested to manufacture components in the automotive industry.
