The high-pressure behaviors of large-diameter single-walled boron nitride nanotubes (BNNTs) are studied by the first-principles method. One sp³-hybridized and three sp²/sp³-hybridized BN allotropes are obtained via compressing large diameter BNNTs. Due to the restricted movement of nonequivalent B and N atoms, the large BN nanotubes have a chance to form B-B and N-N bonds between intertubes under pressure, in addition to the common B-N bonds. The electron localization function and Mulliken's population analysis indicate the covalent nature of the B-B and N-N dimers. The electronic band structure and density of state calculations show a local conducting feature of tP24-BN and superhard semiconducting character of the other three allotropes with indirect band gaps of 1.28 – 3.13 eV.

The oxidation of 3Cr3Mo2NiW and 3CrNi3Mo steels was studied at 600 °C in air, and the test results suggest that the parabolic rate law fitted the oxidation kinetics of both steels. The microstructure, morphology, structure, and phase composition of the oxide film cross-sectional layers of the two Cr-Ni-Mo hot-work die steels were analyzed using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The influences of Cr, Ni, and Mo on the high-temperature oxidation resistance of the two Cr-Ni-Mo hot-work die steels are discussed, and the oxidation mechanism is summarized. Heat-treated samples were analyzed using electron backscattered diffraction (EBSD) to obtain inverse pole figures (IPFs) and average sample grain sizes, and the percentages of twin grain boundaries (TGBs) (θ = 60°) were also measured. After heat treatment, recrystallization was observed in both steels with a large portion of twin grain boundaries. After 10 h of oxidation, the dense chromium-rich oxide layer that formed in the inner oxide layer of 3Cr3Mo2NiW steel effectively prevented the continuation of oxidation. The inner oxide layer in 3CrNi3Mo steel formed an adhesion layer with a network structure composed mainly of Ni- and Cr-rich spinel oxide, without forming a barrier to prevent oxidation.

The uneven distribution and large size of the second phase weakens the effect of dispersion strengthening in ODS-W alloys. In this article, the W-Al₂O₃ composite powders were fabricated using a wet chemical method, resulting in a finer powder and uniformly dispersed Al₂O₃ particles in the tungsten-based alloy. The particle size of the pure tungsten powder is 1.05 μm and the particle size of W-0.2 wt.%Al₂O₃ is 727 nm. Subsequently, the W-Al₂O₃ alloy plates were successfully obtained by induction sintering and rolling processes. Al₂O₃ effectively refined grain size from powder-making to sintering. The micro-hardness of the tungsten alloy plates reached 512 HV_0.2, which is 43.7% higher than that of pure tungsten plates. The nano-hardness reached 14.2 GPa, which is 24.1% higher than that of the pure tungsten plate; the compressive strength reached 2224 MPa, which is 37.2% higher than that of the pure tungsten.

To improve the Al/Steel bimetallic interface, Eu was firstly added to the Al/Steel bimetallic interface made by liquid-solid casting. The effects of Eu addition on the microstructure, mechanical capacities, and rupture behavior of the Al/Steel bimetallic interface was studied in detail. As the addition of 0.1 wt.% Eu, the morphology of eutectic Si changed from coarse plate-like to fine fibrous and granular in Al-Si alloys, and the average thickness of the intermetallic compounds layer decreased to a minimum value of 7.96 μm. In addition, there was a more sudden drop of Fe in steel side and the Si in Al side was observed to be more than the other conditions. The addition of Eu did not change the kinds of intermetallic compounds in the Al/steel reaction layer, which was composed of Al₅Fe₂, τ₁-(Al, Si)₅Fe₃, Al₁₃Fe₄, τ₅-Al₇Fe₂Si, and τ₆-Al₉Fe₂Si₂ phases. The addition of the element Eu did not change the preferential orientation of the Al₅Fe₂, τ₁-(Al, Si)₅Fe₃, Al₁₃Fe₄, τ₅-Al₇Fe₂Si, and τ₆-Al₉Fe₂Si₂ phases, but refined the grain size of each phase and decreased the polar density of Al₅Fe₂ phase. Eu was mainly enriched in the front of the ternary compound layer (τ₆-Al₉Fe₂Si₂) near the Al side and steel matrix. The Fe and Al element distribution area tended to narrow in the interface after the addition of 0.1 wt.% Eu, which is probably because that Eu inhibits the spread of Al atoms along the c-axis direction of the Al₅Fe₂ phase and the growth of Al₁₃Fe₄, τ₅-Al₇Fe₂Si, and τ₆-Al₉Fe₂Si₂ phases. When the Eu content was 0.1 wt.%, the shear strength of the Al/Steel bimetal achieved a maximum of 31.21 MPa, which was 47% higher than the bimetal without Eu.