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Unidirectional rolled (UR) and clock rolled (CR) high purity tantalum sheets were analyzed with an emphasis on the microstructural difference in surface layers. Misorientation characteristics of deformed grains with different orientations are analyzed in detail by visualizing the misorientation angle based on an electron backscatter diffraction dataset. {100}(<100>// normal direction (ND)) grains were found to associate with long-range cumulative orientation changes in CR sample while {111} (<111>// ND) grains were found to contain many micro-shear bands and microbands in UR sample. Then, micro-shear bands and micro-bands were detailedly characterized by transmission electron microscope, and the analysis based on Schmid factor suggested that the primary slip system activated in {111} grains leads to the formation of micro-bands during UR process. Band contrast values were used to evaluate the energy stored in {100} and {111} grains and results showed that the gap of energy between them was narrowed by CR process. Additionally, significant dispersion degree of hardness values indicates the inhomogeneous deformation in UR sample, while different degree in annealed stage indicates the different recrystallization kinetic for UR and CR samples. Upon annealing, nucleation prefers to occur along {111} deformed matrices or {111}-{100} boundaries in UR sample and recrystallization grains are large in size. While nucleation tend to take place in intersected regions in CR sample and recrystallization grains are small, which contributes to the appearance of fine grains in fully recrystallized CR sample. [ABSTRACT FROM AUTHOR]

It is urgent to develop new copper alloys for future fusion reactors (e.g. DEMO and CFETR). This work involved the design and fabrication of an alloy, Cu-0.8Cr-0.12Zr-(0.05Si), with increasing high-temperature softening resistance by thermo-mechanical treatment. The influence mechanism of Si on its mechanical properties and softening resistance at high temperature was investigated. The peak-aged Cu–Cr–Zr alloy containing Si exhibits higher ultimate tensile strength of 622 MPa, yield strength of 588 MPa with a considerable elongation of 17% and electrical conductivity of 76% IACS. The dislocation and Orowan strengthening trigged for finer Cr precipitates are proven to be the main reasons for the improvement in strength. Moreover, the increase in elongation originates from the deformation twins due to the lower stacking fault energy, as confirmed by the first principles. Meanwhile, the addition of Si can significantly improve the high-temperature softening resistance of the alloy. The main reason is that the growth of Cr precipitates is suppressed by adding Si, and its pinning effect on the boundary is better, thereby inhibiting the occurrence of recrystallization. [ABSTRACT FROM AUTHOR]

An investigation on the evolution of annealing twins in a cold rolled (95% thickness reduction) high-purity nickel was reported as a function of annealing temperature. Electron backscattered diffraction (EBSD) analysis revealed that both the grain boundaries migration and the formation of cube texture promoted the proportion of Σ3 boundaries during recrystallization. Moreover, further increasing annealing temperatures showed that the frequency of annealing twins markedly decreases due to encountering of the growing cube-oriented grains one another during grain growth to form new LAGBs. [ABSTRACT FROM AUTHOR]

Abstract: High-purity nickel samples with different volume fractions of initial cube textures were cold rolled to 96% reduction and subsequently annealed at different temperatures. The survived cube orientation fractions in the cold-rolled samples were found to be in proportion to the volume fraction of the initial cube texture. The initial cube fraction could affect the recrystallization process significantly, which showed some huge differences in the case of low temperature annealing from that of high temperature annealing. [Copyright &y& Elsevier]

Commercial purity aluminum (99.5%) was fabricated by equal channel angular pressing (ECAP) up to total accumulated strains of approx. 10. The annealing behavior of material deformed to total strains of approx. 1 and 10 was investigated, using heat treatments of 2 h at various temperatures from 100 to 500 °C. The microstructure of the annealed materials was characterized using the electron back-scatter pattern technique. A number of parameters were determined including the distribution and average values of both the boundary spacings and misorientations. For samples deformed to a total strain of 1, annealing resulted in discontinuous recrystallization. For samples deformed to a total strain of 10, annealing resulted in microstructures exhibiting characteristics of both uniform coarsening and, in a number of places, of discontinuous recrystallization. An attempt was made, based on the boundary spacing distributions, to separate these two components. The grain size after annealing was still however small, being just 6.4 μm after 2 h at 300 °C. [Copyright &y& Elsevier]