MICROSTRUCTURE EVOLUTION AND MECHANICAL PROPERTIES OF ULTRAFINE GRAIN PURE-TI

摘要

A study was made to investigate microstructural evolution and tensile properties of ultrafine grain pure-Ti produced by equal-channel angular pressings. After 4 isothermal equal-channel angular pressings, initial coarse grains (15 μm) were significantly refined to 0.3 μm with homogeneous microstructure which was resulted from 180° rotation of the sample between pressings. Ultrafine grain pure-Ti exhibited the considerable improvement in yield strength while losing strain hardening capacity as compared to coarse grained microstructure at ambient temperature, which was mainly attributed to ultrafine grain microstructure with non-equilibrium grain boundaries. Specifically, such high strength of ultrafine grain pure-Ti was discussed in relation with dislocation model based on dislocation bow-out behavior.