An investigation of the isothermal creep response of Al-based composites by neutron diffraction

Discontinuously reinforced aluminium-based composites containing particulat e or whisker SiC reinforcements at different volume fractions, were produce d via a powder-route. Isothermal creep tests have been carried out at 270, 300 and 320 degrees C. During these tests axial and transverse strains were monitored using a non-contacting laser scanning extensometer arrangement. At the same time neutron diffraction has been used to measure the elastic p hase strain evolution with composite creep deformation. It was found that a fter the initial loading the phase strains remained essentially constant du ring primary and secondary creep. This indicates that the initial matrix/re inforcement inelastic misfits remain largely unchanged, probably due to the setting up of a dynamic equilibrium between misfit generation and stress r elaxation. For each system, the neutron data has been combined with Eshelby modelling to obtain a measure of the load transfer. It was found that whil e the reinforcement often bears the larger share of the load, under certain conditions this is not the case. This would suggest that under these condi tions the presence of the reinforcement is deleterious to the composite cre ep response. (C) 2000 Elsevier Science S.A. All rights reserved.