초미세 결정립 순-Ti의 미세조직 및 상온 인장 물성

Abstract

A study was made to investigate microstructural evolution and mechanical properties of ultra-fine grained (UFG) pure-Ti produced by equal channel angular (ECA) pressings. The deformed structures were analyzed by finite element method and transmission electron microscopy with the increment of straining. After 4 isothermal ECA pressings, initial coarse grains (30 μm) were significantly refined to ~0.3 μm with homogeneous distribution of microstructure which was resulted from 180˚ rotation of the sample between pressings. UFG 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 ultra-fine grain microstructure with non-equilibrium grain boundaries. Such high strength and unusual strain hardening behavior of UFG pure-Ti were discussed in relation with two dislocation models based on dislocation bow-out and dynamic recovery associated with trapped lattice dislocations.