Characteristics of creep deformation in discontinuously reinforced metal matrix composites

Abstract

Recent developments in the creep characteristics of metal matrix composites (MMCs) at elevated temperatures are reviewed. Creep in MMCs is controlled by plastic flow in the matrix materials so that both the matrix alloys and the composites exhibit similar creep properties. When MMCs and their matrix alloys are fabricated using identical powder metallurgy procedures, both sets of material exhibit an increasing apparent stress exponent with decreasing applied stress which is indicative of the presence of a threshold stress. These threshold stresses arise from the presence of fine incoherent oxide particles introduced during atomisation when using powder metallurgy techniques or they may arise from the presence of precipitates in the crystalline lattice when using ingot metallurgy procedures. An additional creep resistance may be introduced in the MMCs by the occurrence of load transfer in which part of the external load is transferred to the reinforcement.