Creep of duplex alumina-titanium nitride polycrystalline microstructures

Compression creep results in an inert atmosphere are presented for fine-grained Al₂O₃-TiN composites deformed under a stress range of 10-50 MPa stress and a temperature range of 1250°-1400°C. The effects of TiN content (10-70 vol%) and the preparation route (i.e., reactive versus nonreactive hot pressing) are considered. Al₂O₃ and TiN both are efficient grain-growth inhibitors, relative to each other; thus, deformation develops in stable equiaxed microstructures. Except for low TiN contents (10 and 20 vol%), the processing route does not markedly influence the observed strain rates, at least up to a strain of -0.16. In all cases, deformation occurs mainly via interfacial/grain-boundary sliding, and its rate is enhanced in approximate proportion to the amount of Al₂O₃/TiN interfacial area. The deformation rate seems to be limited by either some interface reaction or a complex boundary diffusional mechanism that occurs at the Al₂0₃ grain boundaries.