AN INVESTIGATION ON THE CREEP BEHAVOR OFZn-22Al-7SiC(p) COMPOSITE

摘要

Experiments were conducted on Zn-22%Al/7%SiC composite prepared by variable codepositionof multi-phase materials (VCM) to determine the effect of the reinforcement particulates onthe creep deformation behavior in region Ⅰ (low-stress region) and region Ⅱ (intermediate-stress orsuperplastic region) of the sigmoidal plot between stress and strain rate, which was previously reportedfor the reinforcement-free counterpart alloy. The microstructures of the starting material and deformedmaterials were characterized using Scanning Electron Microscope (SEM) and Transmission ElectronMicroscopy (TEM). The experimental data were analyzed and discussed with emphasis on the effect ofthreshold stress, τ0, and the role of the stress dependent matrix substructures. The creep data, whichextend over seven orders of magnitude of strain rate, showed that the apparent activation energy of creep,Qa, which was stress dependent, was higher than that for commercial and high purity Zn-22%Al alloy inregion Ⅰ, while in region Ⅱ the present materials, as the commercial and high purity alloys do, show a Qavalue in good agreement with that anticipated for grain boundary diffusion in the alloy. Themicrostructural data inferred from an examination of the crept specimens suggested that the origin of τ0may be related to the interaction between moving dislocations and dispersion particles; such dispersionparticles most likely represent oxide and nitride particles that are introduced in the material as a result ofprocessing the alloy by thermal spray and deposition.