The effect of cooling rate on the quench sensitivity of 2618 Al/Al2O3 MMC

Metal matrix composites (MMCs) are materials consisting of metal alloys rei nforced with fibers, whiskers, particulates, and wires. Due to their superi or mechanical properties, such as low coefficients of thermal expansion and high specific stiffness, they are attractive for many structural and non-s tructural applications. The most notable production applications are found in the aerospace, automobile, and sports equipment industries. Despite the great potentials possessed by MMCs, there are some concerns regarding the e ffect of the reinforcements, which are mostly ceramics, on the properties o f the matrix alloys. One such property is the quench sensitivity of the mat rix material. Heat treatable aluminum alloys are quench sensitive (i. e. th eir properties and precipitation behavior change with cooling rate or quenc hant). The rate of cooling or the type of quenchant used during the fabrica tion process or the subsequent solution heat treatment affects the mechanic al properties of these materials. Therefore, any modification that can alte r the quench sensitivity significantly could have important consequences on the heat treatment of the alloys. Thus, the quench parameters may have to be more tightly controlled than for the unreinforced alloy in order to main tain consistent as-quenched properties. In the present study, the quench se nsitivity of 2618 Al alloy and its composite containing 10 vol. % Al2O3 par ticles was investigated using hardness measurements and differential scanni ng calorimetry (DSC). Although 2618 Al is quench sensitive, its quench sens itivity was significantly increased by the addition of Al2O3 particles. Als o, cooling rate affected the precipitation kinetics and the volume fraction of the precipitate phases formed in both materials.