Effect of matrix and atmosphere on the creep deformation of aluminum alloy matrix composites

Creep behavior of two types of aluminum alloy matrix composites, which were reinforced with alumina particles and have different matrix alloy, have been investigated at temperatures from 573 to 773 K. Matrices of the composites were 6061 and 2014 Al alloys. The composites contained about 10 or 20 vol.% of alumina particles, the size of which is about 10–30 μm. Creep curves, stress dependence of the minimum creep rate, microstructures after creep deformation and the effect of atmospheres, air and Ar, on the creep behavior were examined. The difference in the volume fraction of the alumina particles does not affect the creep strength for both composites. The effects of the difference in the matrix alloy on creep strength varies depending on temperature. The effects of precipitates and the dissolution of them on the creep strength are discussed. Creep curves of both composites are dominated generally by tertiary creep in air and Ar at every temperature except extremely low stress range at 773 K, where primary creep dominates the creep curves in both atmospheres. Large primary creep strain following a initial inverse type of transient creep, that is S curve, was observed in air in the low stress range at 773 K. In Ar atmosphere, the characteristic S curve and large primary strain were not observed in both composites. The effect of the oxidation on the creep curve, microstructure and creep strain in the extremely low stress range at 773 K are discussed.