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Zn–(< 1 wt%)Mn alloy is a promising base alloy for developing biodegradable Zn–Mn-based alloys with high strength and high ductility. In this paper, the influence of solution heat treatment on microstructure and hardness of as-cast Zn–0.34Mn and Zn–0.76Mn alloys has been investigated. The temperature of 380 °C is a good choice for the solution heat treatment. ζ-MnZn13 phase is completely dissolved in Zn matrix after 20 h for Zn–0.34Mn alloy and after 30 h for Zn–0.76Mn alloy. Unexpectedly, temporary precipitation of ζ-MnZn13 is observed within grains of Zn–0.76Mn alloy at 5 h, which reaches the peak at 10 h and then decreases until it finally disappears. During the solution heat treatment, hardness of the Zn–Mn alloys decreases with time. Zn–0.76Mn alloy is always about 4–8 HV harder than Zn–0.34Mn alloy. The temporarily formed ζ-MnZn13 particles are rod-like or lath shaped. The orientation relationship between a representative lath-shaped ζ-MnZn13 precipitate and Zn matrix can be described as [101]ζ~//[2-1-10]m and (-131)ζ ~ 5.4° from (0002)m, which is firstly reported as far as our knowledge. The ζ-MnZn13 lath has the long axis parallel to [03-32]m and the habit plane parallel to (-111)ζ//(0-113)m. Simulation of lattice matching reveals that every two ζ-MnZn13 lattice sites match with one Zn lattice site along the direction of the long axis, which explains why the precipitate grows along this direction. No serious segregation of Mn is detected within Zn grains in the as-cast Zn–0.76Mn alloy. The reason why ζ-MnZn13 precipitates temporarily form during the solution heat treatment requires further investigation.

Conventional trial‐and‐error method is usually time‐consuming and expensive for multi‐objective optimization of Mg alloys. Although machine learning exhibits great potential to accelerate related research studies, machine learning prediction of properties of Mg alloys is often a prediction of a single target at a time. To address this, this paper integrates non‐dominated sorting genetic algorithm III multi‐objective optimization algorithm with light gradient boosting machine algorithm to simultaneously optimize yield strength, ultimate tensile strength, and elongation of Mg alloys. This is the first time that simultaneous machine learning optimization of these three objectives has been achieved for Mg alloys. This paper combines the non‐dominated sorting genetic algorithm III multi‐objective optimization algorithm with the light gradient boosting machine algorithm to optimize the yield strength, ultimate tensile strength, and elongation of Mg alloys. This is the first time to simultaneously optimize these three‐objective properties of Mg alloys and retain high‐precision predictions for each mechanical property.

Precipitation on deformation defects is essential for enhancing mechanical properties of age-hardenable alloys. In this work, we revealed how {10-12} twin boundary (TB) influences β-Mg17Al12 precipitation in Mg-9Al-1Zn alloy. The precipitates on the TBs are rodlike, while others are lath shape. Most precipitates hold the Burgers orientation relationship (OR) only with twin or matrix. Moreover, certain precipitate variants are absent and a new rule for variant selection on TB is proposed.

Two orientation relationships (ORs) and morphologies with well-defined facets of Mg 2 Sn precipitates in a Mg–Sn–Zn alloy were recently reported. However, the irrational angles of these two ORs were described without explanation. This study reveals that a unique matching-row-on-terrace structure exists in a dominant facet corresponding to either of the observed ORs. The calculated ORs, the orientations of three facets associated with each OR and the terrace-ledge structures in the dominant facets all match well with observations. The present method of row-matching analysis is useful for understanding high-index faceted interfaces and their associated irrational ORs.

The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to the limited slip system in this phase. α grains are mainly rotated from {101¯0} to {0002} during the deformation due to the {101¯2}<101¯1¯> twin. Twin variant selection is found in this study, and the orientation of all {101¯2} twins is oriented at {0002} in different α grains with different deformation degrees. The twin variant selection is well explained based on the strain relaxation along the loading axis and the Schmid factor for twinning shear.

Faceted interfaces are a typical key feature of the morphology of many microstructures generated from solid-state phase transformations. Interpretation, prediction and simulation of this faceted morphology remain a challenge, especially for systems where irrational orientation relationships (ORs) between two phases and irrational interface orientations (IOs) are preferred. In terms of structural singularities, this work suggests an integrated framework, which possibly encompasses all candidates of faceted interfaces. The structural singularities are identified from a matching pattern, a dislocation structure and/or a ledge structure. The resultant singular interfaces have discrete IOs, described with low-index g ’s (rational orientations) and/or Δ g ’s (either rational or irrational orientations). Various existing models are grouped according to their determined results regarding the OR and IO, and the links between the models are clarified in the integrated framework. Elimination of defect types as far as possible in a dominant singular interface often exerts a central restriction on the OR. An irrational IO is usually due to the elimination of dislocations in one direction, i.e., an O-line interface. Analytical methods using both three-dimensional and two-dimensional models for quantitative determinations of O-line interfaces are reviewed, and a detailed example showing the calculation for an irrational interface is given. The association between structural singularities and local energy minima is verified by atomistic calculations of interfacial energies in fcc/bcc alloys where it is found that the calculated equilibrium cross-sections are in a good agreement with observations from selected alloys.

The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to the limited slip system in this phase. α grains are mainly rotated from 101¯0 to 0002 during the deformation due to the 101¯2<101¯1¯> twin. Twin variant selection is found in this study, and the orientation of all 101¯2 twins is oriented at 0002 in different α grains with different deformation degrees. The twin variant selection is well explained based on the strain relaxation along the loading axis and the Schmid factor for twinning shear.

The microstructure evolution of the twin of TB6 (Ti-10V-2Fe-3Al) under planar wave detonation was studied. The initial microstructure of the alloy consists of an α and β phase. It is found that twin deformation is operated in only the α phase due to the limited slip system in this phase. α grains are mainly rotated from 101¯0 to 0002 during the deformation due to the 101¯2<101¯1¯> twin. Twin variant selection is found in this study, and the orientation of all 101¯2 twins is oriented at 0002 in different α grains with different deformation degrees. The twin variant selection is well explained based on the strain relaxation along the loading axis and the Schmid factor for twinning shear.

The transitional state of ordering in the long-period stacking ordered (LPSO) structure in Mg-Al-Gd alloy has been investigated by scanning transmission electron microscopy. It is found that the domains are the origin of observed transitional state. Three new patterns of clusters at this state can be fully explained by the superimposition of L12 type clusters located in different domains. The domains are further verified by different tilted views. Growth of preferred domains during ageing process will result in final ordered LPSO structure. Based on the idea of domains, less ordered LPSO structure in other dilute alloys can be also understood.

Cooperative growth of the structure units (SUs) in a 14H type long-period stacking ordered (LPSO) structure has been observed, and there is no obvious accumulation of transformation strain at the growth fronts. The atomic structures at this front are further characterized by Cs-corrected scanning transmission electron microscopy, and the partial dislocations associated SUs are uniquely defined based on the observations at different zone axes. It is found that the Burgers vectors of neighbouring partials are alternatively opposed so that the transformation strain is self-accommodated. Furthermore, this self-accommodation mechanism is rationalized by the elastic interaction energy for combinations of different partials.