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The present study investigated the effect of Gd on the microstructures and mechanical properties of permanent mould cast Mg-4Al-5RE (wt%) (where RE represents La-Ce mischmetal) alloy. Coarse grains and acicular Al11RE3 phases in Mg-4Al-5RE alloy are successfully refined by the addition of 0.66 wt% Gd. The average grain size is dramatically decreased from 493.9 μm to 205.8 μm, and the acicular Al11RE3 phase is modified to rod-like sharp with a pronouncedly decreased average length from 22.0 μm to 3.8 μm. The modified microstructures are attributed to the formation of Al2(Gd, RE) particles, which act as nucleation sites for both α-Mg and Al11RE3. Eventually, the modified alloy exhibits dramatically enhanced yield strength (YS), ultimate tensile strength (UTS) and elongation (EL) about 12%, 23% and 48%, respectively.

The Al-8Ce-3Y high pressure die-casting alloy was investigated through characterization and first-principles simulation. The alloy shows excellent comprehensive mechanical properties among Al-Ce system alloys. Also it owns a tensile strength of 87 MPa at 350 °C after 200 h holding, which is much superior than Mahle piston Al alloys. Mechanical improvement is attributed to formation submicron Al4(Ce,Y) fiber with Y addition uniformly distributed. Al4(Ce,Y) phase is stable considering formation energy and mixing enthalpy. This study provides superior mechanical performance of Al-Ce alloy to alleviate the low strength at both room and high temperatures.

In recent years, the semisolid processing has received extensive interest because of its noticeable advantages, and a series of criteria have been proposed to assess the processability of semisolid alloys. The aim of this work is to conduct a focused review on the criteria for evaluating the processability of semisolid alloys. It was found that the temperature sensitivity criterion is more commonly adopted, while the time sensitivity criterion has demonstrated a greater adaptability and the enthalpy sensitivity criterion seems to be more reasonable. Despite no general consensus, these criteria actually provide multi-angle evaluation methods for effectively assessing the suitability of semisolid metal (SSM) processing. In the future, the detailed criteria for assessing the semisolid processability of specific alloys need to be further explored, and it is particularly worth extending the evaluation criteria to Mg alloys due to their excellent lightweight effect and potential application, which is expected to attract wide attention of researchers in the semisolid processing field.

A lamellar Mg10GdZn phase was observed near the secondary eutectic β-phase ((Mg,Zn)3Gd) in an as-cast Mg–Gd–Zn alloy. It shows that the Mg10GdZn phase exhibits a 18R-type long period stacking ordered (LPSO) structure, while the lamellae within the α-Mg matrix exhibits a 14H-type LPSO structure. Moreover, it reveals that the hardness and elastic modulus of Mg10GdZn phase are much higher than those of the α-Mg by nano-mechanical measurements.

The real time microstructure evolutions of directional solidification in Mg–Gd alloys are obtained by synchrotron X-ray radiography, and the effects of different low cooling rates under a fixed thermal gradient are studied. Different from the organic alloys, the growth direction of columnar dendrites gradually rotates to the direction of the thermal gradient as the cooling rates increase, which is attributed to the difference of undercooling. Meanwhile, the interface velocity increases but the mean dendrite spacing decreases, and the morphology varies with implication for solute segregation.

We have performed a systematic transmission electron microscopy study of precipitated particles in Mg–Zn–Gd-based alloys after annealing. We find that the Mg–Zn phases and ellipsoidal-shaped icosahedral quasicrystal phases (I-phase) are precipitated and distributed by partition in the grains, which can be attributed to the composition segregation of the alloying elements in the as-cast alloys. The content of alloying element is found to be crucial to the precipitation of nanoscale I-phase. The nanoscale I-phase ranges in size from a few to dozens of nanometers, revealing that the precipitation process satisfies the classical nucleation and growth theory.

An intermediate frequency magnetic field (IFMF) was imposed upon Gd–Mg diffusion couples that were annealed at 773 K. It was found that the average thickness of diffusion layer under the magnetic field was much wider than that without the magnetic field, indicating that the atomic diffusion ability was enhanced. The magnetic field was then applied to the solution treatment of Mg–16.66Gd–0.088Zr (wt%) alloy. Compared with the samples without magnetic field, the area fraction of the eutectic phase (Mg 5 Gd phase) was evidently lower at each time point when the IFMF was imposed during the solution treatment, i.e. the solution treatment process was accelerated by the magnetic field. These two phenomena are mainly due to the enhanced atomic diffusion ability in Mg–Gd alloy under IFMF.

In this study, we have developed an excellent mechanical properties of an ultrafine-grained quasicrystalline strengthened magnesium alloys by conventional extruding as-casted Mg–1.5Zn–0.25Gd (at%) ingot at 373 K with an extrusion ratio of about 9:1. After extrusion, multi-modal microstructure was formed, i.e. exhibited large deformed grains surrounded by fine dynamical recrystallization grains and the mean grain sizes smaller than 1 μm. The extruded sample shows excellent tensile properties at ambient temperature with ultimate tensile strength of 417 MPa, 0.2% proof stress of 395 MPa and elongation to failure of 8.3%. The notable improvement in strength mainly attributed to the grain refinement, dense distribution of the fine precipitates inside the fine dynamical recrystallization grains and the high intensity of typical basal texture.

Magnesium alloys have been currently investigated as potential biodegradable implant materials. In this study, a patent Mg alloy Mg–Nd–Zn–Zr (Jiao Da BioMg, hereafter, denoted as JDBM) was researched as a potential biodegradable stent material in comparison with the clinical trial Mg alloy WE43. The corrosion behaviors of the as-extruded JDBM and WE43 were investigated in artificial plasma by in vitro degradation measurements and cyclic polarization tests. The results showed that the corrosion rate of JDBM was much lower than that of WE43 alloy. Most importantly, the JDBM alloy showed a uniform corrosion behavior in artificial plasma, which could avoid stress concentration as well as a rapid reduction in the mechanical integrity. The investigations indicated that the as-extruded JDBM alloy may be a promising implant material suitable for stent applications.

AZ31 samples were implanted with 90 keV cerium ions with a dose of 1 × 1017 ions/cm2. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS) and Glancing angle X-ray diffraction (GAXRD) were used in order to investigate the characterization of elements in the implanted surface. The results indicate that after cerium implantation a pre-oxidation layer with double structure was formed. The influence of cerium implantation on the cyclic oxidation behaviour of AZ31 samples was studied at 773 K in air for 96 h, and the morphologies of the oxide scales were examined by scanning electron microscopy (SEM). It was found that the oxidation resistance of the implanted sample has been improved. The mechanisms to explain the experimental results were also proposed.

As-cast microstructures of Mg–5Zn–2Nd–1.5Y–0.6Zr–0.4Ca electromagnetic casting alloy were characterized in detail, revealing the presence of W-phase (Mg 3 RE 2 Zn 3 ) at grain boundaries. After hot extrusion at 643 K with two extrusion ratios of 38 and 22 respectively followed homogenization at 673 K for 16 h, the alloy showed an ultrafine grain size of 2–5 μm due to dynamic recrystallization in the course of hot extrusion, and exhibited a high strength of 357 MPa at room temperature, which can partially be attributed to the MgZn 2 type Laves phase precipitating during hot extrusion.

A new equal channel angular extrusion (ECAE) processing, two-step ECAE, was applied to control the microstructure and mechanical properties of AZ31 Mg alloy. The ultra-fine grain size of 0.5 μm has been produced, and both the ductility and yield stress of the alloy were significantly increased after the processing, which is ascribed to grain refinement as well as incomplete dynamic recovery and recrystallization during the second-step ECAE at 453 K.

Compared with traditional direct chilling casting (DC) ingot, the edge and center microstructures of Φ270 mm low-frequency electromagnetic casting (LFEC) ingot are fine and uniform; and the macrosegregation is also greatly reduced. When the electromagnetic intensity is kept as 9000 At, with decreasing the frequency, the center microstructures are much finer and the macrosegregation is much lower. In the range of frequency employed in the experiments, the optimum frequency is found to be 15 Hz.

The composite electroforming technology was propounded to fabricate silicon carbide powder (SiC p ) reinforced copper-based composites. The influences of the concentration of SiC p in plating solution, the temperature of plating solution and current density on the SiC p content in Cu/SiC p composites were studied. Results showed that it could promote codeposition of Cu and SiC p and increase SiC p content in composites effectively through optimizing the technology parameters. Results of the study on thermal and mechanical properties of Cu/SiC p composites indicated that with SiC p content (vol.%) increasing, bend strength and HV (Vickers hardness) increased, but coefficient of thermal expansion (CTE) and conductivity factor decreased. In addition, internal stress existed in Cu/SiC p composites, which had influences on HV and thermal expansion property of Cu/SiC p composites.

In situ composites of Zn–27Al–6.3Mg–3.7Si alloy have been fabricated by centrifugal casting using the heated permanent mold. This kind of composites is consisted of three layers: inner layer segregates lots of blocky primary Mg2Si and a little blocky primary Si, middle layer does not contain primary Mg2Si and primary Si, outer layer contains a little primary Mg2Si and primary Si. The position, quantity and distribution of primary Mg2Si and primary Si are determined by solidification velocity under the effect of centrifugal force and their floating velocity inward. The inner and outer layer contained primary Mg2Si and primary Si exhibit much higher hardness and wear resistance than the middle layer.

A new type of patented biodegradable biomedical magnesium alloy Mg–Nd–Zn–Zr (hereafter, denoted as JDBM) was prepared in this study. The biocorrosion properties of the as-extruded JDBM alloy were investigated in simulated body fluid (SBF) by hydrogen evolution, mass loss and electrochemical tests. The biocorrosion properties of as-extruded AZ31 and as-extruded WE43 alloys as well as the mechanical properties at room temperature were also studied in order to compare with the novel JDBM biodegradable biomedical magnesium alloy. The results show that the as-extruded JDBM alloy not only owns much better mechanical properties at room temperature but also exhibits much better biocorrosion properties in SBF.

Hot-tearing susceptibility of Mg–9Al– x Zn alloys is studied. Crack-ring molds were used to test the hot-tearing susceptibility. In situ thermal analysis, optical microscopy, scanning electron microscopy (SEM) and line scan were used to examine the hot-tearing behavior. Hot-tearing originates along the grains at the end of solidification. With Zn additions, the quantity of phase with low melting point in grain boundaries is increased, its melting point is decreased and the hot-tearing susceptibility is increased. The segregation of Zn element in grain boundaries is the main contribution to the high hot-tearing susceptibility of Mg–9Al– x Zn alloys.