The Effect of Different Annealing Temperatures on Recrystallization Microstructure and Texture of Clock-Rolled Tantalum Plates with Strong Texture Gradient

Abstract

The texture and the bulk stored energy along the thickness direction were extremely inhomogeneous in the clock-rolled tantalum sheets with 70% reduction. Therefore, the effects of different annealing temperatures on the microstructure and texture distribution of tantalum plates through the thickness were investigated by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The results showed that the occurrence of strong {111} recrystallization texture in the center layer can be attributed to the subgrains nucleation mechanism when annealed at the low temperature. Many subgrains with {111} orientation appeared in the center layer, due to its high stored energy and preferential nucleation sites of the {111} deformed matrix, and rapidly grew into the effective nucleus, resulting in the large {111} grain size and strong {111} texture after complete recrystallization. Contrarily, at the high temperature, high-angle grain boundaries had sufficient driving force to generate migration, due to the lack of recovery, and the growth time of recrystallized nucleus was much shorter, contributing to relatively uniform recrystallization microstructure and texture distribution along the thickness.

Numerical simulation of microstructure evolution of high-purity tantalum during rolling and annealing

“…The dimensions of tantalum plate, mill roll and the technical parameters of rolling and annealing are consistent with experiments [7,8,16]. The radii of the upper and lower rolls are 500 mm, the rolling temperature and speed are 20 • C and 0.2 m s −1 , and the thickness of the tantalum plate before rolling is 20 mm.…”

“…Like other BCC metals, tantalum undergoes thermoplastic deformation during rolling, with its grains elongated in the rolling direction and compressed in the normal direction, resulting in significant shear bands at its grain boundaries [14][15][16][17][18][19]. When the rolling temperature is lower than 800 K, the tantalum plate does not undergo dynamic recrystallization during rolling [20,21], while the static recrystallization occurs during annealing [7,8]. Therefore, our model studied the microstructure evolution of high-purity tantalum from three aspects: thermoplastic deformation during rolling, static recrystallization and grain growth during annealing.…”

“…Tantalum recrystallization was observed during the annealing process after rolling [7,8]. When the annealing temperature is above 1000 K, the microstructure evolution is dominated by static recrystallization and grain growth [20,24].…”

“…Liu et al [6] used circumferential rolling not only to weaken the uneven texture distribution in the initial tantalum plate, but also to effectively improve the microstructure and storage energy distribution. Zhu et al [7,8] found that large {111} grains appear in the center layer at low temperature annealing and the size of recrystallized grains was relatively uniform at high temperature annealing, while the large grains appear in the surface layer if the annealing time is too long after cold rolling. Some researchers have also studied the microstructure evolution of pure tantalum metal under rolling and annealing by various numerical models.…”

Texture and Microstructure Evolution of Ultra-High Purity Cu-0.1Al Alloy under Different Rolling Methods

“…Cu thin film, used as the basic component, can greatly affect the performances of integrated circuits, which also indicates the possible directions to optimize the properties of devices by improving the quality of the Cu film. Among numerous factors changing the quality of the thin film, the sputtering target with features of high purity, grain refinement, random orientations, and large scale should be considered primarily due to the following reasons: (i) Only Cu and Cu alloy targets with purities of 6 N or above can well ensure the uniformity of sputtering film and the fine wiring quality [5]; (ii) the finer the grain is, the faster the sputtering rate is, while the more homogeneous grain size has more uniform deposition rate and sputtering film [6,7]; (iii) for face-centered cubic (FCC) metals, the sputtering rate is S (111) > S (100) > S (110) [8,9], while the atomic line density is L (110) > L (100) > L (111) , indicating that the random crystallographic orientations of the sputtering target can improve the uniformity Crystals 2021, 11, 1113 2 of 12 of film [7,10,11]. Clearly, the uniform and fine grain size combined with random orientations in the target can improve the quality of the sputtering film.…”