Title: Creep damage behaviour of Al6061-Al2O3 particulate composites

Authors: Maurizio Vedani, Elisabetta Gariboldi

Addresses: Politecnico di Milano, Dipartimento di Meccanica, Piazza L. da Vinci 32, 20133 Milano (Italy). Politecnico di Milano, Dipartimento di Meccanica, Piazza L. da Vinci 32, 20133 Milano (Italy)

Abstract: Aluminium-based particulate reinforced composites were developed to enhance stiffness, wear resistance and mechanical properties. Their tensile and creep resistance at temperatures up to 250°C is generally limited due to reduced high temperature properties of the matrix alloys. However, scientific research is extremely active in this field and many fundamental research works are carried out in order to understand the effects of particulate addition on matrix high temperature behaviour. The aim of the present investigation was the evaluation of high-temperature creep damage properties of two Al6061-Al2O3 particulate reinforced composites having different reinforcement volume fractions (10 and 20 vol.%). Short- and medium-term creep tests were performed at 150 and 250°C. Fractographic analyses and microstructural observations on longitudinally sectioned samples were carried out in order to assess the existence and localisation of creep damage as well as to identify creep damage mechanisms. It was stated that creep of the two particulate MMC was mainly controlled by aluminium matrix deformation and that the mechanical interaction between matrix and reinforcement generally played a minor role. The matrix/particle interaction heavily affected the last stage of creep deformation, when the occurrence of microstructural damage led to the final fracture. Differences in the mechanical behaviour at 250°C of the two materials was explained by means of SEM analysis as the result of different microstructural damage mechanisms. In addition, the Rabotnov-Kachanov model was adopted to describe the damage evolution during creep of the two alloys. The model, which takes into account a simple damage parameter and which derives the material parameters from experimental creep curves, was able to clearly distinguish between the different damage evolutions related to interface debonding and particles fracture.

Keywords: Al6061-Al2O3p composites; creep damage; high temperature behaviour; metal matrix composites.

DOI: 10.1504/IJMPT.2002.001313

International Journal of Materials and Product Technology, 2002 Vol.17 No.3/4, pp.243-260

Available online: 13 Dec 2003 *

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