A novel method to enhance the performance of an ex-situ Al/Si-YSZ metal matrix composite

Abstract

A novel technique was used to synthesise an Al–Si/YSZ composite with improved bonding strength between the matrix and YSZ particles. Based on thermal analysis results, Bi was added in slurry state at 605 ± 5 °C, and two-step stirring was applied. It was found that the duration of mushy zone decreased and solidification rate increased with the addition of YSZ particles. Elemental mapping analysis on etched and deep-etched conditions revealed that these YSZ particles were surrounded by Bi. Mechanical characterisation showed that YS, UTS, El% and the hardness of the A356 + Bi/YSZ composite increased by 25.5%, 2%, 43% and 24% respectively. Fractography analysis confirmed that the interfacial bonding strength at Al/YSZ improved significantly with the addition of Bi. The wear rate and friction coefficient of A356 + Bi/YSZ decreased to 0.464 and 0.55 mm3/Km respectively, which are 34.6% and 6.7% lower than the values obtained for the A356/YSZ composite. The worn surface revealed mild abrasion wear mechanisms in the A356 + Bi/YSZ composite.