MICROSTRUCTURAL REFINEMENT OF Ti BILLETS BY EQUAL CHANNEL ANGULAR PRESSING

摘要

This paper reports the effect of prior deformation on the refinement of microstructure in commercial purity (CP) titanium subject to equal channel angular pressing (ECAP). CP Ti Grade 2 billets were subject to multiple-strike isothermal forging before ECAP. Microstructures and mechanical properties were observed after the initial forging and then after 1, 2, 3, and 4 passes of ECAP. Grain size reduction from 50 μm to 1 μm by forging makes it possible to create a uniform ultrafine-grained structure with an average grain size of 0.6 μm after 2 ECAP passes. This is comparable to the grain size obtained after 8 ECAP passes without prior forging. Moreover, this kind of treatment resulted in a yield strength of 750 MPa in contrast to 680 MPa obtained after 8 ECAP passes.