EFFECT OF THERMAL-STRESS ON THE MICROSTRUCTURES OF ALUMINUM METAL-MATRIX COMPOSITES

Discontinuous reinforced aluminium metal matrix composites have been s ynthesized using nanocrystalline mullite and zirconia of diameters ran ging between 20-30 nm prepared by a sol-gel route. Uniaxial hot pressi ng technique was used to prepare the composites in the temperature ran ge varying between 450-610 degrees C, close to the matrix metal solidu s. The thermal stress-induced evolution of microstructures of the Al m etal matrix were characterised by applying X-ray diffraction line prof ile analysis in terms of the defect parameters such as particle (domai n) sizes, root mean square strains, lattice parameter changes, disloca tion densities etc. The microhardness (Vickers) values of the composit es have been measured and correlated with the values of thermal stress along with other parameters depicting the matrix microstructures. (C) 1998 Elsevier Science S.A.