Effects of microstructure and texture evolution during the industrial ECAE and recrystallization on tensile properties of pure niobium

Abstract

Abstract Straight extrusion (SE), single equal channel angular extrusion (S-ECAE) and double equal channel angular extrusion (D-ECAE) were performed in pure niobium on an industrial scale. Effects of the number of angular passes on microstructure and texture during extrusion and subsequent recrystallization in the niobium were investigated. Compared with the SE, the ECAE processes are beneficial to increase the misorientation of the sub-structures, and many high angle boundaries formed in niobium during the D-ECAE. The intensity of texture in the recrystallized niobium decreases with the increase of the number of angular passes. After recrystallization the D-ECAE grains are only with a few micrometers, and random orientation distribution appeared. The strain hardening rate of niobium during tension testing shows an obvious decrease after the S-ECAE process. The optimal tensile properties with ultimate tensile strength of 346 MPa and elongation of 41.5% have been obtained in the D-ECAE niobium after recrystallization. The mechanical performance has a significant improvement due to the ultra-fine grains and random orientations obtained by the twice industrial angular extrusions.