The effect of second phase on the creep deformation of 6061Al matrix composites.

Creep behaviour of two types of 6061Al matrix composites, which were reinforced with 10 and 20 vol.% of alumina particles or II and 18 vol.% of alumina short fibers, have been investigated at temperatures ranging from 573 to 773 K. Creep curves, stress dependences of the minimum creep rate and the microstructure after creep deformation were examined. A quantitative analysis of creep curves was also carried out by the theta-projection method. The difference in the volume fraction of the reinforcing second phases does not affect the creep strength in both types of composites. Creep strength of the fiber reinforced composites is higher than that of the particle reinforced ones at 673 and 773 K. Parameters determined by theta-projection method are able to describe the creep curves of the composites quantitatively. It has been shown that the precipitation of the solute atoms influences the creep behaviour at 573 K in both composites. The existence of the soft regions around the second phase is suggested in the particle reinforced composite crept under low stress at 773 K. (C) 1997 Elsevier Science S.A.