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Through molecular dynamics simulations, this study investigates the orientation and temperature dependence of the tensile mechanical properties, the failure mechanism, and crack propagation characteristics of MgAl2O4 single crystal. The results reveal significant anisotropy and temperature sensitivity in the mechanical properties of MgAl2O4. Particularly, [111]-oriented MgAl2O4 exhibits the highest elastic modulus and ultimate tensile strength but a relatively minor failure strain. In the 300 K to 2100 K temperature range, the elastic modulus, ultimate tensile strength, and failure strain decrease with increasing temperature. At 2100 K, MgAl2O4 exhibits excellent structural stability and high-temperature strength. The failure mechanism is a brittle fracture initiated by the continuous convergence of vacancies into micropores/microcracks. The propagation of microcracks is influenced by crystal orientation and slip bands. Nevertheless, high temperatures significantly accelerate crack propagation, leading to premature failure. This study provides guidelines for preparing MgAl2O4 with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

In this work, the interfacial structure, adhesion properties, and electronic structure of the Al(001)/MgAl2O4(001) interface are investigated via density functional theory calculations. Considering different termination atoms and stacking sites, six interfacial models are explored. The results show that the OAlO-terminated O-top stacking configuration has the greatest interfacial adhesion work of 2.51 J m−2. The nature of bonding between atoms at the Al(001)/MgAl2O4(001) interface is determined by analyzing their interfacial electronic structures, such as valence charge density difference, Bader charge, and density of states. The atoms of the Al(001)/MgAl2O4(001) OAlO-terminal exhibit not only the Al-Al metal bonding but also ionic bonding. For the O-top and two hollow configurations, Al-O covalent bonding components are also present, which mainly originate from the coupling between the Al-3p and O-2p orbitals. In turn, the OAlO-terminated O-top stacking configuration possesses deeper negative energy bands in the Al-O resonance peaks of the interfacial atoms than the OAlO-terminated hollow stacking configuration, resulting in stronger interfacial bonding. Finally, the OAlO-terminated O-top stacking interface corresponds to the most stable interfacial structure. [ABSTRACT FROM AUTHOR]

In the present work, the molecular dynamics (MD) simulation is employed to investigate the tensile and compressive deformation behavior of nano-polycrystalline Ti with the mean grain size of 6.8 nm. The deformation behaviors reveal that the nano-polycrystalline Ti has different deformation mechanisms under the tension or compression. When the nano-polycrystalline Ti is applied tensile loading, the dislocation density quantification shows that there is no significant new dislocation appearing before the tensile strain reaches the failure strain (ε = 0.12). Instead, a 25° difference in the grain boundary misorientation angle between two grains was observed, which indicates that the grain boundary rotation and sliding are appeared to dominate the tensile deformation process of nano-polycrystalline Ti. When the nano-polycrystalline Ti is applied compressive loading, the compressive stress increases linearly with the increase in compressive strain before the compressive strain arrives 0.075. Once the compressive strain exceeds 0.075, the nano-polycrystalline Ti enters the plastic deformation stage. In this case, the hcp-Ti atoms near the grain boundary were firstly transformed to the bcc-Ti atoms and then the hcp-Ti atoms within the grain transforms into the bcc-Ti atoms with the increase in compressive strain, which indicates that the plastic deformation of nano-polycrystalline Ti during the compression is dominated by the phase transformation from hcp-Ti to bcc-Ti. In addition, it is found that the deformation behaviors of nano-polycrystalline Ti are sensitive to strain rate and temperature. The present work could be beneficial for the design and fabrication of nano-polycrystalline Ti alloys with excellent mechanical properties. [ABSTRACT FROM AUTHOR]