Creep behaviour of a SiC particulate reinforced Al-2618 metal matrix composite

Abstract

The creep behaviour of Al-2618 reinforced by approximately 10 μm SiC particles has been characterized by constant strain rate tests at 438 K and 493 K, followed by careful measurement of stress, work hardening during primary creep and extensions to failure. The high stress exponents recorded for secondary creep are comparable to literature values for other particle reinforced MMCs and decrease with test temperature. This can be interpreted by a combination of a recoverable internal stress generated by load partition and a creep threshold stress. A critical strain rate above which a sudden transition in creep behaviour occurs is clearly visible at 10 −4 s −1 with the material tested at 493 K. Identical material tested at 438 K shows a much less pronounced transition in behaviour at strain rates above 3 × 10 −7 s −1. However, both these values are found to be consistent with a diffusional relaxation model for internal stress recovery during creep deformation. Data from these tests fall on a common activation line with other particle dispersed Al alloys consistent with a bulk diffusion relaxation process.