INTERNAL-STRESS AND MICROSTRUCTURE OF SIC REINFORCED ALUMINUM-ALLOY-2014

Precipitates and interfaces in a SiC particulate reinforced AA 2014 al loy have been characterized by high-resolution transmission electron m icroscopy and X-ray microanalysis. The kinetics of precipitation and t he lattice parameter and microstress variations during ageing of the c omposite were studied by X-ray diffraction at elevated temperature. Th e kinetics of precipitation in a composite sample and a stress-free re ference powder differ substantially. Thermal misfit stresses induced b y SiC particulates increase the rate of precipitation by approximately a factor three, but do not influence the type or total amount of prec ipitates. Due to the different precipitation rates, X-ray diffraction measurements of three-dimensional stresses must be made with caution; discrepancies between the sample and the reference powder compositions may give erroneous results. There is no evidence of interfacial react ions between the particulates and the matrix alloy, or of pore formati on or preferential precipitation at the interfaces. (C) 1998 Acta Meta llurgica Inc. Published by Elsevier Science Ltd. All rights reserved.