Carbon nanotubes (CNTs) reinforced aluminum-based composites exhibit characteristics such as low density, high specific strength, and high specific stiffness, making them promising materials for applications in aerospace, automotive lightweighting, and other fields. The dispersion of CNTs in the aluminum matrix and the strength of the interface between CNTs and the aluminum matrix are crucial for the preparation of CNTs reinforced aluminum-based composites. In this study, CNTs were surface-modified with partial coating of Al2O3, and then the CNTs reinforced 2195 aluminum-based composite (2195/CNT composite) were prepared using a combination of melting-casting process and hot extrusion. The tensile strength, yield strength, and elongation of the aged 2195/CNT composite reached 697 MPa, 590 MPa, and 11.3 %, respectively, demonstrating a significant improvement in mechanical properties compared to 2195 alloy prepared under the same conditions. CNTs were primarily present at grain boundaries, and a small amount of glow stick-like Al4C3 phase was found near the CNTs. The formation of glow stick-like Al4C3 phase was attributed to the segregation of solute elements at the interface in the alloy. First-principles calculations revealed that solute elements tended to segregate at the interface closer to the aluminum matrix. Moreover, the segregation of Cu and Ag elements at the interface could enhance the cleavage energy of the Al4C3/Al interface, while the segregation of Mg elements reduced the cleavage energy of the interface. This study also analyzed the reinforcement mechanisms involved in the 2195/CNT composite.

Aluminum and its alloys are known to be susceptible to hydrogen embrittlement, however, current experimental techniques face significant challenges in directly observing hydrogen atom distributions and their interactions with microstructural features in Al alloys. In this study, we investigate hydrogen-enhanced decohesion at Al/Al₃Li interfaces in Al alloys using a systematic first-principles approach. Our results demonstrate that hydrogen atoms preferentially occupy at strained locations within both Al and Al₃Li phases, with the Al/Al₃Li phase exhibiting a stronger trapping capability at the Al/Al/Al₃Li interface. This hydrogen distribution leads to reduction in cohesive strength of Al/Al₃Li interface. Moreover, we show that the extent of hydrogen-enhanced decohesion on Al/Al₃Li interface is influenced hydrogen concentration and temperature. These findings provide fundamental insight into hydrogen trapping and embrittlement mechanisms at Al/Al₃Li interfaces and offer guidance for designing Al–Li alloys with improved hydrogen resistance through targeted control of composition and microstructure. 

Interstitial elements play a complex role on shear deformation in Ni, however, current experimental techniques face limitations in observing interstitial elements distribution and their interaction with the micro-structures in Ni. In this work, first-principles calculations have been used to investigate solubility behaviors of interstitial solutes (H, B, C, N, and O) in bulk Ni with the variables of component and strain. Moreover, the solute segregation behaviors at the stacking faults and their effects on stacking fault energies have been evaluated with a focus on the H-induced localized plasticity phenomenon, while H-X solute pair competitions in Ni has also been discussed in detail. Finally, the variations of shear moduli and stacking fault energies of Ni with the presence of interstitial solutes have been evaluated and their correlation has been proposed. The results revealed a strong effect of volumetric strain on interstitial solute segregation in Ni, while stacking faults acted as potential traps for interstitial solutes. The H-induced localized plasticity has also been proved in terms of stacking fault energy. Our findings aim to contribute to the development of strategies to strengthen Ni alloys that are utilized in the complex chemical environment, thereby mitigating shear failure and enhancing the critical shear stress of Ni alloys.

The solute segregation and its effects on the cohesion of the Fe/Y₂Ti₂O₇ interface in ferritic oxide dispersion strengthened (ODS) alloy have been investigated using first-principles calculations. The computational results indicate that W, Cr, Al, Nb, Zr, and Hf are prone to segregate to the Fe/Y₂Ti₂O₇ interface and enhance the cohesive strength of the Fe/Y₂Ti₂O₇ interface, improving its stability. He atoms exhibit a strong tendency to segregate at the Fe/Y₂Ti₂O₇ interface, leading to embrittlement of the interface. Moreover, in the case of co-existing of W, Cr, Al, Nb, Zr, and Hf with He atoms, it is found that W, Cr, and Al increase the segregation energy of He at the Fe/Y₂Ti₂O₇ interface. This promotes the diffusion of He from the Fe/Y₂Ti₂O₇ interface into the bulk of the Y₂Ti₂O₇, thereby reducing He-induced embrittlement at the Fe/Y₂Ti₂O₇ interface. Finally, the electronic structures of the Fe/Y₂Ti₂O₇ interfaces with and without solute elements, as well as the interaction between metallic solutes and He, have been discussed in detail to reveal the mechanisms of alloying reduction effect on He-segregated embrittlement at the Fe/Y₂Ti₂O₇ interface. The results obtained from this work suggest that adjusting the alloying components in ODS alloys can improve the radiation resistance of the alloy, providing theoretical guidance for the design and optimization of ferritic ODS alloys.

A first-principles investigation on the effect of O-doping and W-addition as well as O-W coexistence effect on the Ni/Ni3Al interface in Ni-based alloys is performed. The results reveal that O occupies octahedral interstitial sites while W substitutes for Ni or Al atoms at the Ni/Ni3Al interface. O significantly reduces the interface cohesive strength, while W enhances the cohesion of the Ni/Ni3Al interface. In the cases of O-W co-existence, O and W maintain their individual weakening and strengthening effects, in most cases, the weakening effect of O-doping is more pronounced. When O is located in the coherent (002)γ/γ′ layer, the fracture strength and toughness of the co-doping interface are even worse than when O doped alone. Furthermore, the influence of O-W co-doping on the interface appears insensitive to the atomic distance between O and W. Electronic structure analysis reveals that the embrittling effect of O originates from its local electron aggregation effect, while W results in a strengthening effect at close range and a slight weakening effect at longer distances in the interfacial region. The findings provide insights into the complex effects of multiple elements interactions and suggest a potential strategy for the design of Ni-based alloys. 

The microstructure and mechanical properties of the Al_0.7CoCrFeNiCu high-entropy alloy (HEA) were studied in both as-cast state and annealed state, and the results showed that the alloy was composed of FCC1, FCC2, and BCC phases. Cu-rich and Fe-Cr-rich precipitates were present within the BCC phase, while small amounts of needle-like precipitates were observed in both the FCC1 and the FCC2 phases. After annealing at 700°C, the matrix phase composition of the alloy did not change significantly, but the volume fraction and size of the needle-like precipitates increased with the holding time. The hardness and yield strength first increased and then decreased with the extension of the holding time, reaching peak values at 48 h of holding time of 364 HV and 667 MPa, respectively. During annealing at 900°C, the volume fraction of needle-like phases first increased and then decreased with prolonged holding time, while the precipitates underwent significant coarsening. The hardness and yield strength reached peak values at 1 h of holding time of 311 HV and 493 MPa, respectively. During the subsequent holding process, as the needle-like phase significantly coarsened, the mechanical properties of the alloy steadily declined, which led to the overall mechanical properties after annealing at 700°C being superior to those after annealing at 900°C.

The oxidation behavior of AlCoCrFeNiCu_0.5 high-entropy alloy (HEA) in air at both 800 °C and 900 °C has been analyzed and corresponding microstructural evolution after oxidation has also been studied. The experimental studies revealed that the as-cast AlCoCrFeNiCu_0.5 alloy is mainly composed of BCC and FCC phases, moreover, there is a spinodal structure with the constituent phases being NiAl-B2 and FeCr-BCC. After annealing at 900 °C for 6 h, the spinodal structure disappeared, but there was σ phase at grain boundary. Oxidation caused significant changes in the matrix of the alloy. The primary phases of the oxidized matrix are the NiAl-B2 phase and FeCoCr-FCC1 phase. A substantial amount of Al was consumed in matrix to form Al₂O₃ on the surface, resulting in the formation of Al-depleted layer. The longer the oxidation time, the thicker the Al-depleted layer, and a concentrated distribution of Cu-rich FCC2 phase was observed in this region. The isothermal oxidation kinetics of the alloy at both 800 °C and 900 °C followed the parabolic law. The k_p values for oxidation at 800 °C and 900 °C were 7.367 × 10^− 14 (g²·cm^− 4·s^− 1) and 2.105 × 10^− 13 (g²·cm^− 4·s^− 1) respectively, indicating that the kp value at 900 °C was 2.86 times that at 800 °C. A continuous Al₂O₃ layer on the surface being the key to its superior oxidation resistance of the HEA at both temperatures.

This study investigates high-entropy CrMnFeCoNi alloys with reduced Co content using density functional theory. The muffin-tin orbital method and coherent potential approximation successfully predict experimental values for volume, magnetic moment, and elastic constants. Thermodynamic properties, analyzed using the Debye–Gruneisen model, emphasize the need to consider both electronic and magnetic contributions to the free energy. The alloys exhibit anti-Invar behavior, with a significant increase in the linear thermal expansion coefficient with increased temperature. This effect is slightly more pronounced for reduced Co content, leading to a larger lattice parameter and a decrease in elastic constants. However, the changes are small, suggesting that similar mechanical properties can be achieved with lower Co content.

The oxidation behavior of the Fe-9.96Ni-10.7Cr-6.49Al-0.25Zr-3.49Mo- 0.005B (wt%) (FBB8) alloy at 800 ℃ and 900 ℃ was investigated and the microstructural evolution of the oxide layer and substrate was also analyzed. The mechanisms by which zirconium doping influences the oxidation behavior of FBB8 are investigated, and a dynamic segregation mechanism is utilized to explain the differing effects of Zr at 800 ℃ and 900 ℃. At 800 ℃, the slow diffusion of Zr results in an oxide layer predominantly composed of alumina, during which Zr inhibits the diffusion of cations. In contrast, at 900 ℃, a composite oxide structure is formed, with zirconium dioxide embedded within Al2O3, leading to accelerated oxidation of the alloy. The NiAl phase acted as an aluminum reservoir during oxidation at 900 ℃. However, due to its small area-to-volume ratio, Al could not diffuse to the oxide scale/alloy surface, leading to internal oxidation in the alloy. This research provides a foundation for understanding the reactive element effect and offers data support for the development of Zr-containing alloys.

This study investigates the thermodynamic and mechanical properties of Y4Zr3O12 and Y2Ti2O7 oxides in ferritic alloys with and without Helium utilizing a systematic first-principles approach. Firstly, the atomic arrangement of Y and Zr atoms at cation 18f sites in δ-(Y–Zr–O) oxide is identified, while it is found that Y4Zr3O12 exhibits a more robust formation tendency than Y2Ti2O7. Furthermore, it is noted that both Y4Zr3O12 and Y2Ti2O7 oxides demonstrate a prior ability to trap Helium compared to the bcc-Fe matrix, which leads to a substantial enhancement on the stiffness of both oxides. The elastic moduli of both Y4Zr3O12 and Y2Ti2O7 oxide exhibit a gradual increase with the growing Helium concentration. As a result, the enhanced shear modulus of oxides and sustained shear modulus of the bcc-Fe matrix collectively contribute to the overall strength of ferritic alloys under Helium environments. The findings in this work propose valuable insights for guiding critical strategies in the design of high-performance oxide-dispersion-strengthened ferritic alloys, particularly for applications in Helium environments.