On plastically-accomodated creep in an inclusion bearing material

The creep behavior in a discontinuous fiber-reinforced metal-matrix composi te without other interfacial relaxation mechanisms than matrix plastic flow has been examined. The existence of steady-state creep is revealed from th e following four points First, it is pointed out that the variation princip les do not prove the existence of the energy minimum state and the creep te rmination. Second, it is shown that for viscous matrix material, creep cont inues with the same strain as elastic, which is important and does not chan ge the stress distribution. Third, finite element method (FEM) analysis rev eals steady-state creep. Without the constant dilation option, an incorrect result of the creep termination is obtained. At last, the creep behavior o f AL-AI,Ni in situ composite is measured experimentally. At high stresses, a stress exponent of 5 and an activation energy of 130 kJ mol(-1) are obtai ned, showing plastic accomodation, while at low stresses, 1 and 85 kJ mol(- 1) are obtained showing diffusional accomodation. (C) 2000 Elsevier Science S.A. All rights reserved.