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• High-strength Ti 2 AlNb sheet was fabricated by hot packed rolling the spark-plasma-sintered pre-alloyed powders. • Extreme high tensile strength of 1532 MPa without any post heat treatment was obtained after two rolling passes. • The micro-sized O and nano-sized O phases contributed to the high tensile strength of the sheet. In this work, we fabricated high-strength Ti 2 AlNb sheets by hot packed rolling the spark-plasma-sintered pre-alloyed powders at the B2 + O phase field. We rolled the sheets with three different schemes, namely, sheet A (thickness reductions of 42% + 42%), sheet B (30% + 30% + 30%), and sheet C (30% + 21% + 21% + 21%). Results showed that the spheroidizing of the O phase occurred during the multiple rolling processes, and sheet C consisted of only spherical O phases. The mechanical property tests showed that Ti 2 AlNb sheets with tensile strengths higher than 1400 MPa could be obtained without any post heat treatment. Both micro-sized O and nano-sized O phases contributed to the excellent mechanical properties of the sheets. The multiple rolling processes resulted in slight decreases in tensile strength but an increase in ductility. All sheets showed brittle fracture mode with reduction of area smaller than 5%. [ABSTRACT FROM AUTHOR]

• Ti x VNbMoTa refractory high-entropy alloys with ultra-fine grains were fabricated by MA and SPS. • The mechanical alloying time of the milling powders with high Ti content was extended by the severe agglomeration. • The fluctuation of yield strengths is attributed to the changes of strengthening effect. Ti x VNbMoTa refractory high-entropy alloys (RHEAs) were fabricated by mechanical alloying (MA) and spark plasma sintering (SPS) based on classic VNbMoTaW RHEA. The effect of Ti content on the microstructures and mechanical properties of the Ti x VNbMoTa RHEAs were systematically investigated. The results showed that the milling powders with more Ti content were agglomerated severely in the early stage of the MA process, leading to the extension of mechanical alloying time. The mechanically alloyed powders in all groups exhibited single body-centered-cubic (BCC) phase after the MA process. The sintered alloys were consisted of ultra-fine matrix and precipitation phase. The grain sizes of the matrix and precipitation phases, as well as the volume fraction of the precipitation phases were increased with the increase of Ti content. The MA and SPS processes and the replacement of Ti not only greatly reduce the densities, but also significantly improved the ductility, strength and specific strength of the alloys. The yield strengths were decreased first and then increased with the increase of Ti content in the Ti x VNbMoTa RHEAs, which is mainly attributed to the weakened effect of grain boundary strengthening, and the enhanced effect of the substitution solid solution strengthening and the interstitial solid solution strengthening. The rapidly increased sizes and volume fractions of the precipitated phases in Ti1.5 and Ti2 destroyed the continuity of matrix and the coordination of deformation, resulting in the decrease of ductility. [ABSTRACT FROM AUTHOR]

• DFT and AIMD were combined to study the oxidation mechanism of CrN. • Surface energy of CrN low-index surface was calculated. • The adsorption configuration and electronic structure were analyzed. • The dynamics process of O 2 dissociation and adsorption was studied by AIMD. • The PDOS change during AIMD simulation were analyzed. [Display omitted] Density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD) are combined to investigate the CrN oxidation mechanism. The surface energy, adsorption configuration and electronic structure of oxygen molecule and atom on the CrN (100) surface are investigated through DFT calculation. AIMD calculation is used to investigate the geometric configuration and electronic structure evolution of O 2 molecule adsorption and dissociation process at 1073 K. Results show that the (100) surface has the lowest surface energy. The top site of Cr atom is the most stable adsorption site for oxygen molecules and atoms, and the adsorption energy values are −4.276 eV and −4.975 eV, respectively. Charge density difference results show that both oxygen molecule and atom undergo charge transfer with the Cr atom. The O atom gains electrons while the Cr atom loses electrons. Results of partial density of states show that the Cr O bond is formed due to the hybridization between the O-p and Cr-d orbitals. At 1073 K, AIMD results show that the O 2 molecule automatically dissociates into O atoms, and the dissociated O atoms form stable covalent bonds with the surface Cr atom. The hybridization between the O-p and Cr-d orbitals gradually increases, thereby forming stable adsorption. [ABSTRACT FROM AUTHOR]