Thermal shock behaviour of particle reinforced 2618 Al/Al2O3 MMC

Discontinuously reinforced metal matrix composites (DRMMCs) based on alumin um alloys are fast becoming the materials of choice in many structural and non-structural applications. They have the unique combination of strength, stiffness, coefficient of thermal expansion and affordability as well as th e capability to be manufactured by conventional metal processing methods. T he most notable production applications ar e found in the aerospace, automo bile, electronics and sports equipment industries. Despite the great potent ial possessed by MMCs, there are still some concerns regarding the effect o f the reinforcements. which are mostly ceramics, on the properties of the m atrix alloys. Among these is the thermal shock resistance of the matrix mat erial. Some of the applications in which DRMMCs are bound to find themselves will inevitably involve an element of thermal cycling where components will be s ubjected to rapidly changing stress states and thus thermal shock damage. I n the present study, the thermal shock behaviour of 2618 Al alloy and its c omposite containing 10 vol.% Al2O3 particles was investigated using hardnes s measurements, scanning electron microscopy (SEM) and differential scannin g calorimetry (DSC). Under cyclic thermal shock conditions, the matrix allo y failed by matrix cracking at the surface, whereas the reinforcing Al2O3 p articles simply shattered. Also, thermal shock treatment affected the preci pitation kinetics and the volume fi action of the precipitate phases formed in both materials.