S.F. Liu

Elimination of Elongated Bands by Clock Rolling in High-Purity Tantalum

Abstract135-deg clock rolling was developed to process high-purity Ta plate aiming to remove the elongated bands occurred in unidirectionally rolled sample. Results showed that compared to unidirectional rolling, clock rolling facilitated the split behavior of {100} grains and could diminish the stored energy difference between {111} orientation and {100} orientation. Consequently, the nucleation ability of {100} grain was enhanced, which should contribute to the disappearance of the elongated bands.

Strain accommodation of -normal direction-oriented grains in micro-shear bands of high-purity tantalum

AbstractThe <110>ND(<110>//normal direction)(<110>ND) grains in micro-shear bands in high-purity tantalum were investigated using electron backscatter diffraction and X-ray line profile analysis. The generation of the <110>ND grains and their subdivision and rotation behaviors upon the subsequent deformation were characterized by multi-scale analysis methods based on information about the slip systems, misorientation angle/axes and stored energy. The obtained results show that in the transverse plane, <110>ND grains are oriented at angles of 15°–25° to the adjacent deformed matrices in the 60% rolled specimen, and at angles of 25°–35° in the 87% rolled specimen. The <110>ND grain provided strain accommodation during the shear deformation. Moreover, the energy of the <110>ND grains in the 87% rolled specimen is approximately three times larger than that in the 60% rolled specimen, indicating that the role of strain accommodation is enhanced with the increase in the micro-shear stress concentration in a local region in tantalum.

Through-thickness texture gradient of tantalum sputtering target

For sputtering targets, through-thickness texture is critical for assuring reliable sputtering performance. In this paper, through-thickness texture gradient of a rolled and subsequently annealed tantalum sputtering target was investigated. The results show that by carefully controlling the rolling process, shear-related components at the surface of the rolled sample could be avoided. Both the rolled sample and the annealed target develop a through-thickness texture gradient with the formation of a stronger {1 1 1} fiber in the center layer compared with that in the surface layer.

Revealing substructure in clock-rolled Ta aided with triple focused ion beam

Clock rolling was developed to make deformation microstructure homogenize in high-purity Ta. The substructure of deformed Ta was revealed by electron back-scatter diffraction (EBSD) technique aided with triple focused ion beam (FIB). The results indicate that the triple FIB method can produce a mirror surface required by EBSD analysis. The clock rolling works well for the homogenization of deformed microstructure. Particularly, the local stored energy in {111} orientated grains is largely reduced by clock rolling, whereas it is enhanced in {100} orientated grains because of the occurrence of grain subdivision.