Pure polycrystalline Zr was deformed by equal channel angular pressing, and the microstructural characteristics were analyzed. By repeated alternating equal channel angular pressing, it was possible to refine the grain size from 200 to 0.2μm. Subsequent annealing heat treatment at 550C resulted in a grain growth of up to 6μm. Mechanical twinning was an important deformation mechanism, particularly during the early stage of deformation. The most active twinning system was identified as 85.2º {10▪2}<¯10▪1> tensile twinning, followed by 57.1º {10▪1}<¯10▪2> compressive twinning. Crystal texture as well as grain-boundary misorientation distribution of deformed Zr were analyzed by X-ray diffraction and electron back-scattered diffraction. The equal channel angular pressing-deformed Zr showed a considerable difference in the crystallographic attributes from those of cold-rolled Zr or Ti, in that texture and boundary misorientation-angle distribution tend toward more even distribution with a slightly preferential distribution of boundaries of a 20 to 30º misorientation angle. Furthermore, unlike the case of cold rolling, the crystal texture was not greatly altered by subsequent annealing heat treatment. Overall, this suggested that equal channel angular pressing was a viable method to obtain significant grain refining in hexagonal close-packed metals.

Microstructure Evolution in Zr under Equal Channel Angular Pressing. W.S.Choi, H.S.Ryoo, S.K.Hwang, M.H.Kim, S.I.Kwun, S.W.Chae: Metallurgical and Materials Transactions A, 2002, 33[3A], 973-80