Texture Evolution of Niobium Single Crystal Processed by Interrupted ECAE

H.R.Z. SANDIM; R.E. BOLMARO; HEIDE HELOISE BERNARDI

Campinas

Congreso; XV Brazilian MRS. XV SBPMAT; 2016

Brazilian MRS

Niobium has a body-centered cubic structure and it has unique properties like a high melting point, high ductility even at cryogenic temperatures, superconductivity, good corrosion resistance, and also biocompatibility [1, 2]. However, pure niobium has low tensile strength, and in some specific applications a high value is mandatory. Strength might be improved by severe plastic deformation, for example, equal channel angular extrusion (ECAE). The sample was analyzed by light optical microscopy, Vickers hardness testing and the changes in texture through the extrusion channel were determined by X-ray diffraction and the results were compared with those reported in the literature for deformed bcc materials and with those predicted using the viscoplastic selfconsistent (VPSC) model [3]. The present work describes the texture evolution of a niobium single crystal deformed by 1 pass in an interrupted ECAE experiment using a die angle of θ = 120o, and the results show that initial texture is rotated of 60° (θ/2) around the axis TD (transversal direction) when the sample is extruded through the shear zone of the channel, and this rotation remains constant until the final deformation. After passing through the channel, the niobium has a single texture component identified as (¯1¯12)[111]. Moreover, deformation inhomogeneities (bands) are shown elongated and at an angle of 60° with the extrusion direction (ED). This angle coincides with the main shear plane of an ECAE matrix with θ = 120o.