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In this work, a novel "spark plasma sintering (SPS) of pre-alloyed powder followed by a hot packed rolling" method is proposed to fabricate the Ti 2 AlNb sheet. Ti 2 AlNb sheets with high tensile strength and good ductility are obtained without any post heat treatment. Ti 2 AlNb compact is first prepared by SPS of the pre-alloyed powders. The compact sintered at 1060 °C consists of only B2 phases with an average grain size of 25.88 μm. No α 2 phase forms after rolled at 1030 °C and the B2 grain size increases by increasing the rolling passes because of the fast grain growth of B 2 grains. Numerous ultrafine O phases precipitated inside the B 2 matrix after cooled in air, and they contribute to the excellent strength and ductility of the sheets. The mechanical property tests showed that the sheets rolled by 2 passes (thickness reduction: 42% + 42%) and 4 passes (30% + 21% + 21% + 21%) had the maximum tensile strength of 1239.03 MPa and the maximum elongation of 9.49%, respectively. All the rolled sheets presented ductile fracture mode with numerous dimples on the fracture surface. • A novel "SPS of pre-alloyed powder followed by hot packed rolling" method is proposed to fabricate Ti 2 AlNb sheet. • Ti 2 AlNb sheets with high strength and good ductility can be obtained without any post heat treatment. • The nano-sized O phases precipitated from B 2 matrix contribute to the excellent properties of the sheets. [ABSTRACT FROM AUTHOR]

In this study, the scanning electron microscope (SEM) and electron backscattering diffraction (EBSD) was used to investigate the evolution of the TiB whiskers (TiBw) orientation, microstructure, and texture during hot rolling. The mechanical properties at room-temperature were tested for as-rolled composites in different loading directions. Based on the calculated and measured Schmid Factors (SFs), the effect of texture on the modes of dislocation slip in different directions was researched. A generalized shear-lag model was modified to evaluate the strengthening contribution of TiBw in different directions. The effects of matrix texture, TiBw orientation, and Hall-Petch (H–P) relationship on the anisotropy of mechanical properties of as-rolled composites were comprehensively analyzed. Results show that recrystallization (DRX) mechanisms include continuous DRX (CDRX) and discontinuous DRX (DDRX) during hot rolling. When the rolling reduction was 70%, the matrix alloy displayed the {11 2 ‾ 0} <10 1 ‾ 0> texture (the crystal c-axis point to the TD, i.e. T-Texture) and recrystallization texture. With the increase of rolling reduction, the strength of as-rolled composites increased. The best mechanical properties were obtained in the rolling direction (RD) at 60% rolling reduction, in which the tensile strength and plasticity were increased by 14% and 17.3% respectively compared with as-sintered composites. The prismatic slip and the basal slip were activated in RD and transverse direction (TD) respectively during room-temperature tensile. The strengthening contribution of TiBw decreases from RD to TD. Analysis of the synergistic effect of TiBw load-transfer reinforcement and H–P reinforcement on property anisotropy shows that the combination of the H–P relationship and TiBw orientation weakens the as-rolled composites anisotropy. 1. The microstructure and texture evolution of TiBw/TA15 during hot rolling is analyzed. 2. The Schmid Factors of different slip systems for ideal T-texture are calculated. 3. The shear-lag model is modified to evaluate the strengthening effect of TiBw. 4. The synergistic effects of TiBw and grain size on the anisotropy are analyzed. [ABSTRACT FROM AUTHOR]

The hot deformation behaviors of an ultrafine-grained MoNbTaTiV refractory high entropy alloy (RHEA) fabricated by powder metallurgy (P/M) were investigated using isothermal compression tests in the deformation temperature range of 1100 °C ~ 1300 °C and the strain rate range of 0.0005 s−1–0.5 s−1. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) techniques were used to analyze the effect of the deformation temperatures and the strain rates on the flow stress behaviors and microstructural evolution during hot deformation. The results showed that the flow stresses exhibit typical dynamic recrystallization (DRX) characteristics, but show work hardening characteristics at 1100 °C and 0.5 s−1 deformation conditions and at 1200 °C and 0.5 s−1 deformation conditions. With increasing deformation temperature and decreasing strain rate, the maximum compressive stresses were dramatically decreased, and the average grain sizes also slowly increased. The limited growth of grains was due to the sluggish diffusion effect of high entropy alloys (HEAs) and the pinning effect of the ultrafine precipitated phases. The dominant DRX process gradually changed from discontinuous dynamic recrystallization (DDRX) to continuous dynamic recrystallization (CDRX) with increasing deformation temperature and decreasing strain rate. Both of these DRX processes were promoted by the ultrafine precipitated phases. The dominant deformation mechanism at low deformation temperature and high strain rate was grain deformation. Grain boundary gliding became the dominant deformation mechanism at higher deformation temperature and lower strain rate, but it was inhibited to some extent by grain growth and the ultrafine precipitated phases distributed at grain boundaries. [ABSTRACT FROM AUTHOR]