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While there have been multiple recent reports in the literature focusing on the effects of magnetic field on the phase transformation behaviors, the research conducted with an ultra-high magnetic field greater than 20 T is still preliminary. In the current study, the structure evolution of Co-B alloys are experimentally studied with undercooling. The effects of a 25 T magnetic field on the solidification behavior and the subsequent solid-state phase transformation behavior have been investigated. The 25 T magnetic field is confirmed to have little effect on the homogeneous nucleation, but have some influence on the heterogeneous nucleation of Co3B and Co23B6 phases by modifying the wetting angle θ. The decomposition of Co23B6 phase in the subsequent cooling process can be effectively suppressed by applying the 25 T magnetic field. The present work might be helpful for not only theoretically understanding the influence of ultra-high magnetic field on the phase transformation behaviors but a potential technology of field-manipulation of magnetic materials.

Entropy-stabilized multi-component alloys have been considered to be prospective structural materials attributing to their impressive mechanical and functional properties. The local chemical complexions, microstates and configurational transformations are essential to reveal the structure–property relationship, thus, to promote the development of advanced multi-component alloys. In the present work, effects of local lattice distortion (LLD) and microstates of various configurations on the equilibrium volume (V0), total energy, Fermi energy, magnetic moment (μMag) and electron work function (Φ) and bonding structures of the Fe–Mn–Al medium entropy alloy (MEA) have been investigated comprehensively by first-principles calculations. It is found that the Φ and μMag of those MEA are proportional to the V0, which is dominated by lattice distortion. In terms of bonding charge density, both the strengthened clusters or the so-called short-range order structures and the weakly bonded spots or weak spots are characterized. While the presence of weakly bonded Al atoms implies a large LLD/mismatch, the Fe–Mn bonding pairs result in the formation of strengthened clusters, which dominate the local microstates and the configurational transitions. The variations of μMag are associated with the enhancement of the nearest neighbor magnetic Fe and Mn atoms, attributing to the LLD caused by Al atoms, the local changes in the electronic structures. This work provides an atomic and electronic insight into the microstate-dominated solid-solution strengthening mechanism of Fe–Mn–Al MEA.

The site occupancy of boron (B) in L12 γ′-Ni3Al and its (010) antiphase boundary (APB) are studied by first-principles calculations in the present work. Based on the electronic structures of the (010) APB, 12 initial tetrahedral sites for B are identified and reduced to 6 distinct configurations due to symmetry, which are transformed into 4 octahedral sites presented by the atomic trajectories during relaxations in first-principles calculations. It is revealed that B atoms prefer to occupy a site far away from the fault layers within the (010) APB of γ′-Ni3Al, agreeing well with previous experimental observations. Bonding charge density is utilized to provide a novel insight into the local L12 → D022 structural phase transformation of the APB and the corresponding tetrahedral-octahedral transition. The energetic site occupation of B is dominated by the lower electron density of the octahedral sites than that of tetrahedral sites.

Based on the growing power of computational capabilities and algorithmic developments, with the help of data-driven and high-throughput calculations, a new paradigm accelerating materials discovery, design and optimization is emerging. Titanium (Ti) alloys have been chosen herein to highlight an integrated computational materials engineering case study with the aim of improving their strength and ductility. The electronic properties of elemental building blocks were derived from high-throughput first-principles calculations and presented in the form of the Mendeleev periodic table, including their electron work function (Ф), Fermi energy (EF), bonding charge density (Δρ), and lattice distortion energy. The atomic and electronic insights of the composition–structure–property relationships were revealed by a data mining approach, addressing the key features/principles for the design strategies of advanced alloys. Guided by defect engineering, the deformation fault energy and dislocation width were treated as the dominating criteria in improving the ductility. The proposed yield strength model was utilized quantitatively to present the contributions of solid-solution strengthening and grain refinement hardening. Machine learning was used collaboratively with fundamental knowledge and feed back into a new training model, shown to be superior to the empirical molybdenum equivalence method. The results draw a conclusion that the integration of data mining and machine learning will not only generate plausible explanations and address new hypotheses, but also enable the design of strong and ductile Ti alloys in a more efficient and cost-effective way.

Two-dimensional (2D) materials with the advantage of low interlayer shear strain are ultilized as lubricants in aerospace and precision manufacturing. Moire superlattices (MSL), with attractive physical properties of electronic structures, interlayer hybridization and atomic forces, have been widely investigated in superlubricity, which is caused by elimination of interlayer lock-in by incommensurate atomic reconstruction. Although the foundations of superlubricity and the development of 2D lubricants via vanishing friction have been investigated, it is still important to comprehensively reveal the influence of MSL on the interlayer van der Waals (vdW) interactions of 2D lubricants. Here, the contributions of lattice distortions of solute-doped twisted bilayers (Mo, X)S2 (X = Al, Ti, V and Cr) to superlubricity are comprehensively investigated by high-throughput modelling and DFT-D2 calculations. It is revealed that the lattice distortion not only breaks the interlayer balance of repulsion and van der Waals interactions but also yields layer corrugation. These layer-corrugation-induced changes of the interlayer interactions and spacing distances are utilized to optimize lubricity, which matches with the experimental friction coefficients in the order of (Mo, Al)S2 > (Mo, Cr)S2 > MoS2 >(Mo, V)S2 >(Mo, Ti)S2. The evolutions of the band structures show an exponential relationship of the band edge width and layer deformations, paving a path to accelerate the development of advanced superlubricity materials via lattice distortions.

This article presents a brief review of our case studies of data-driven Integrated Computational Materials Engineering (ICME) for intelligently discovering advanced structural metal materials, including light-weight materials (Ti, Mg, and Al alloys), refractory high-entropy alloys, and superalloys. The basic bonding in terms of topology and electronic structures is recommended to be considered as the building blocks/units constructing the microstructures of advanced materials. It is highlighted that the bonding charge density could not only provide an atomic and electronic insight into the physical nature of chemical bond of materials but also reveal the fundamental strengthening/embrittlement mechanisms and the local phase transformations of planar defects, paving a path in accelerating the development of advanced metal materials via interfacial engineering. Perspectives on the knowledge-based modeling/simulations, machine-learning knowledge base, platform, and next-generation workforce for sustainable ecosystem of ICME are highlighted, thus to call for more duty on the developments of advanced structural metal materials and enhancement of research productivity and collaboration.

Two-dimensional (2D) materials with the advantage of low interlayer shear strain are ultilized as lubricants in aerospace and precision manufacturing. Moiré superlattices (MSL), with attractive physical properties of electronic structures, interlayer hybridization and atomic forces, have been widely investigated in superlubricity, which is caused by elimination of interlayer lock-in by incommensurate atomic reconstruction. Although the foundations of superlubricity and the development of 2D lubricants

With the quick development of high-speed railway and the service of the series of CRH (China Rails High-speed) for almost a decade, one of the greatest challenges is the managements/maintenances of those trains in environmental conditions. It is critical to estimate the intergranular corrosion damage initiations and propagations, thus, to setup the relative database in order to support foundations for an interactive corrosion risk management. In this work, ∑ 3 0 1 1 1 1 ¯ 1 coherent twin boundary (CTB) of FCC Al–X is utilized to reveal the interactions between interstitials (X = H, N and O) and CTB together with their embrittlement mechanism. The HCP-type fault layers within the CTB are same as those fault layers in growth fault, indicating the local FCC-HCP transformation at CTB and revealing the physical foundation for those criteria designing growth twins. The notable accumulation of bonding electrons of interstitial atoms occupying either T-site or O-site yields a dramatically reduction of Al–X and Al–Al bonding charge density and bonding strength, revealing the embrittlement mechanism of Al CTB.

In this work, effects of solute atoms (X) on lattice parameters, bulk modulus, enthalpy of formation, lattice distortion energy, electron work function (EWF) and bonding morphology/strength of HCP Ti95X are comprehensively studied by first-principles calculations. Here, X includes the α-stabilizer Al, and the β-stabilizer Cr, Mo, V and Nb, which are commonly combined in the high-strength Ti7333 and Ti5553 alloys. Attributing to various atomic size and number of valence electrons of these solute atoms, the mechanical (lattice distortion) and the chemical (solute atom) contributions to the local lattice strains are clearly distinguished in terms of lattice distortion energy and bonding charge density. It is found that the equilibrium volume of Ti95X decreases linearly with the increased HCP volume of each solute atom. The less change of volume yields minimum lattice distortion energy. Moreover, a higher value of Δρ caused by the electron redistributions of solute atoms than the matrix indicates an improved bonding strength via the coupling effects of lattice distortion and valence electrons. The bonding strength of Ti95X increases in the order of Ti-Al

In the present work, the effect of solute atoms on the lattice parameters, atomic volume, stacking fault energies ( $$ \gamma_{\text{SF}} $$ ), bulk modulus, and bonding structures of HCP Ti is studied comprehensively by first-principles calculations. Here, the alloying effects on the growth fault (I1), deformation fault (I2) and extrinsic fault (EF) are considered, with the solute atoms (X = Al, Cr, Mo, Nb, and V) commonly utilized in the high-strength Ti-7333 and Ti-5553 alloys selected. It is found that the stacking fault energies of pure Ti increase in the order of $$ \gamma_{\text{I1}} $$ V > Cr > Mo > Nb for I1 and I2 and V > Al > Cr > Nb > Mo for EF, respectively. The bonding charge density is utilized to characterize the electronic redistributions caused by the fault layers and the lattice distortions. It is presented that the rod-type bonds of the non-fault layers change into the tetrahedral-shaped bonds of fault layers, displaying the local HCP–FCC-type phase transformation. With the addition of various solute atoms with different atomic size and valance electrons, the bond strengths of Ti–Al and Ti–Nb are weaker than those of Ti–Cr and Ti–Mo as there are fewer densities of bonding electrons. This work gains some insights into the atomic and electronic basis for the solid-solution strengthened bulk and stacking faults of HCP Ti, providing fundamental information to the development of advanced high-strength Ti alloys.

Brittle compounds and large residual stresses are easily formed at the diffusion bonding (DB) joints of dissimilar intermetallic compounds, which will deteriorate the performance of the joints. In this study, in order to conduct an in-depth study of the strengthening mechanisms, the post-bonded heat treatment (PBHT) and post-bonded hot deformation (PBHD) were applied to the TiAl/Ti2AlNb DB joint. Comparative studies were implemented aiming to reveal the strengthening mechanisms and their influence on interfacial microstructure and mechanical properties. The experimental results indicated that the harmful intermetallic compound AlNb2 phase in the DB joint was eliminated by PBHT and PBHD. Meanwhile, the diffusion layers were changed from O + (AlNb2+α2) + (α2+β/B2+γ) three layers of DB joints to (α2+β/B2+O + Ti3NbAl2) + (α2+β/B2+γ) two layers of PBHD joint. Interestingly, the Ti3NbAl2 phase was first found in the DB joint after PBHD. After testing, the tensile strength and the relative tensile strength (defined as the tensile strength ratio of the joint and the TiAl alloy) of samples increased by 272.54 MPa and 39.2% after PBHD, respectively. In comparison, the tensile strength and the relative tensile strength of samples increased by 75.96 MPa and 10.96% after PBHT. This demonstrated that PBHD could induce the formation and uniform dispersion of the Ti3NbAl2 phase, which is indispensable to improve the tensile strength of the TiAl/Ti2AlNb DB joint.

In the present work, the localized corrosion and stress corrosion cracking (SCC) behaviors of a commercial 6005A-T6 aluminum extrusion profile was studied comprehensively. The velocity of crack growth in self-stressed double-cantilever beam (DCB) specimens under constant displacement was estimated, which also provides insight into the local microstructure evolutions at the crack tips caused by the localized pitting corrosion, intergranular corrosion (IGC), and intergranular SCC. Characterizations of local corrosion along the cracking path for a period of exposure to 3.5% NaCl were revealed via optical microscope (OM), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The typical features of the pits dominated by the distribution of precipitates included the peripheral dissolution of the Al matrix, channeling corrosion, intergranular attack, and large pits in the grains. The discontinuous cracking at the crack tips indicated the hydrogen-embrittlement-mediated mechanism. Moreover, the local regions enriched with Mg2Si and Mg5Si6 phases and with low-angle grain boundaries presented better SCC resistance than those of the matrix with high-angle grain boundaries, supporting a strategy to develop advanced Al–Mg–Si alloys via interfacial engineering.

The electronic structures and properties of ten TiAl/Ti2AlNb heterogeneous interfaces with three Ti2AlNb phases (B2, D019, O) and different terminations/boundaries were comprehensively studied via first-principles calculations. Their interfacial bonding features, strength and relative stability are quantitatively and qualitatively revealed by the equilibrium energy, Fermi energy, interfacial energy (γint), electron localization function and bonding charge density (Δρ), respectively. Accordingly, it was revealed by the partial and total electron density of states that the decreasing tendency of the bond strength in the order of Ti-Nb > Ti-Al > Nb-Al at the interfaces was attributed to the electrons hybridization of Ti-d states, Nb-d states and Al-p states. Since the γint decreased in the order of TiAl/B2 > TiAl/O > TiAl/D019, the TiAl/D019 interfaces with the lowest energy was regarded as the most stable phase boundaries and was further validated by the electron back-scattered diffraction analysis. It is found that the D019 phase is dominated at the interface boundaries while the B2 serves as a transition phase distributed on its both sides. On the contrary, the metastable O phase can form in the bulk Ti2AlNb but not at the interface due to their largest distortion when precipitating at the phase boundary. This work provides an insight into the atomic and electronic basis for the bonding and strengthening mechanisms of TiAl/Ti2AlNb heterogeneous interfaces.

Here, the nature of intergranular corrosion features and mechanisms for commercial 5083-H111, 6082-T6 and 6005A-T6 Al alloys are investigated comprehensively, supporting foundations for their management and maintenances under environmental conditions. It is found that the localized corrosions including the pitting, intergranular corrosion (IGC), exfoliation together with their coupling effects tend to the follow the direction and the morphology of precipitations and the elongated rolling/extrusion directions, suggesting grain refinement would be an effective approach to enhance the strength and IGC resistance. The microstructure characterizations and orientation statistics reveal the indicators improving durability and damage tolerance properties in the development of advanced Al alloys.

Y-junction carbon nanocoils (Y-CNCs) were synthesized by thermal chemical vapor deposition using Ni catalyst prepared by spray-coating method. According to the emerging morphologies of Y-CNCs, several growth models were advanced to elucidate their formation mechanisms. Regarding the Y-CNCs without metal catalyst in the Y-junctions, fusing of contiguous CNCs and a tip-growth mechanism are considered to be responsible for their formation. However, as for the Y-CNCs with catalyst presence in the Y-junctions, the formation can be ascribed to nanoscale soldering/welding and bottom-growth mechanism. It is found that increasing spray-coating time for catalyst preparation generates agglomerated larger nanoparticles strongly adhering to the substrate, resulting in bottom-growth of CNCs and appearance of the metal catalyst in the Y-junctions. In the contrary case, CNCs catalyzed by isolated smaller nanoparticles develop Y-junctions with an absence of metal catalyst by virtue of weaker adhesion of catalyst with the substrate and tip-growth of CNCs.