Rationalization of Plastically-Accommodated Steady-State Creep of a Composite

Abstract

Composite creep deformation was analyzed, based on a continuum plasticity representation of the matrix, in an ideal composite at high temperatures in the case of negligible interfacial diffusion and sliding. A general formula of the steady-state creep strain rate was derived for a composite consisting of an ellipsoidal rigid reinforcement and a creeping matrix with a stress exponent of one. A closed-form solution was then derived for a composite with a cylindrical reinforcement under pure shear deformation in a two-dimensional analysis. The resultant creep deformation satisfies the requirements of impotency, volume conservation and interfacial continuity. Traces of two types of edge dislocations were analytically drawn; they show that dislocations climb over the reinforcement, retaining no dislocations either in the matrix or at the interface. Also, two types of dislocations simultaneously climb up and down at any portion in the matrix through dislocation core shuffling without long-distance diffusion. Finally, it was concluded that plastically-accommodated creep is characterized by two types of dislocations that simultaneously climb over a reinforcement, generating a heterogeneous creep strain increment without long-distance diffusion.

High-Temperature Creep Mechanism of Dual-Ductile-Phase Magnesium Alloy with Long-Period Stacking Ordered Phase

“…In addition, they showed that load was no longer transmitted to the rigid reinforcing phase at zero interfacial strength, and that the creep strength under such a situation was lower than that of the matrix alone. Sato et al 13,14) studied the creep behaviors of MMCs with rigid reinforcing phases and showed that composite weakening and dispersion strengthening occurred in the low-stress region, where the strain gradient was +1 This Paper was Originally Published in Japanese in J. Japan Inst. Met.…”