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To investigate the influence of the morphology and amount of quasicrystal I phase on discharge performance, a comparative study is conducted on the discharge characteristics of Mg-2.4Zn-0.4Y (ZW-1), Mg-3.6Zn-0.6Y (ZW-2), and Mg-4.8Zn-0.8Y (ZW-3). As the content of Zn and Y rises, the amount of quasicrystal I phase increases, and its morphology transforms from dot-like to strip-like structures. ZW-1 exhibits the best corrosion resistance and discharge performance, followed by ZW-2, with ZW-3 performing the worst. Based on the electrochemical results and characterization, the quasicrystal I phase can enhance the dissolution of the magnesium anode throughout the discharge process. Nonetheless, an excess of the quasicrystal I phase increases galvanic corrosion, leading to unstable discharge voltage and reduced anode efficiency.

In this study, micro-nano hybrid SiCp/7075Al composites were successfully prepared for the first time by ultrasonic-assisted semi-solid stirring casting method. The effects of micro-nano hybrid SiCp on the microstructure and mechanical properties of 7075 Al were studied. The results show that the distribution of SiCnp and micron SiCp in the microstructure was uniform. During the extrusion process, most of the micron SiCp were subjected to significant load and broken, which increased the contact area with the matrix and promoted the interface bonding. In addition, the enhanced interfacial interaction promoted the formation of MgAl2O4 phase, which significantly improved the mechanical properties. SiCnp not only had a significant effect on grain refinement, but also promoted the enrichment of Cu, accelerated the formation of GP zone, and promoted the formation of more nano-MgZn2 precipitates. The yield strength and the elastic modulus of micro-nano hybrid SiCp/7075 Al composites reached 450 MPa and 94 GPa, respectively. The synergistic effect of SiCnp and micron SiCp could produce composite strengthening effects such as load transfer strengthening, thermal mismatch strengthening and Orowan strengthening. Moreover, a large number of dislocation pile-ups were observed near the interface between micron and nano SiCp and Al matrix. This leaded to a higher work hardening rate of the composites as the particle content increases. The higher work hardening rate enhanced the strain hardening ability of the material during plastic deformation, thereby significantly improving the tensile strength and elongation of the material.

Traditional magnesium structural materials are used widely due to their light weight; however, their corrosion resistance is poor. In order to address this problem and improve the strength simultaneously, SiCp-, SiCnp-, and SiCnw-reinforced Mg-2Zn-0.1Y (wt. %, MZY alloy) matrix composites (SiC/MZY composites) with the same contents (0.3 wt. %) were prepared and extruded at low temperature in this paper. The effects of SiC morphology on the microstructure, mechanical properties and corrosion resistance of MZY alloy were studied. The results show that the grain size can be refined by adding SiC reinforcement. Compared with the unreinforced MZY alloy, the strengths of the SiC/MZY composites were all improved, with a yield strength of more than 440 MPa and an ultimate tensile strength of more than 450 MPa. However, only the corrosion rate of the composites reinforced by submicron SiCp was improved significantly. The hydrogen evolution corrosion rate (PH) was reduced by 81% relative to the MZY alloy. This can be attributed to the decreased galvanic corrosion pairs, as well as the decreased potential difference between the second phase and the matrix in the SiCp/MZY composite. Additionally, a compact product film on the surface of the SiCp/MZY composite can also protect the matrix. The materials prepared in this study showed excellent strength and high corrosion resistance at relatively low cost, providing valuable insights and design ideas for the development and application of those materials in marine and offshore engineering applications.

In this paper, three sizes (5, 20 and 50 μm) SiC particles (SiCp) were selected, and the SiCp/Mg–6Zn–1Gd-0.3Ca (SiCp/ZG61X) composites with ∼50 vol.% were successfully prepared by squeeze casting. The effect of particle size on the properties of the composites was studied, while the wear resistance and the wear mechanism of composites were investigated. The results showed that compared with the matrix alloy, the addition of SiCp can significantly improve the properties of the composites, in which the strength increased from 175.2 to 326.5 MPa and the modulus increased from 45.0 to 159.6 GPa. At the same time, the coefficient of thermal expansion and friction were significantly reduced. In addition, the smaller the particle size, the higher the strength and modulus of the composite. However, for the coefficient of friction and thermal expansion, the larger particle size was conducive to the reduction of the two coefficients. The analysis of friction and wear behavior showed that the wear mechanism of the matrix alloy was mainly abrasive wear and adhesive wear, while the wear mechanism of the composites was abrasive wear and layered wear.

A large amount of lamellar phases were precipitated in Mg-9Gd-xAl (x = 0.4, 0.6, 0.8, 1.0, 3.0 wt.%) alloy after solution treatment. In order to explore the composition and formation condition of the lamellar phase, the Mg-9Gd-xAl alloys were subjected to solution treatment at different time, then the influence of lamellar phase on mechanical properties was investigated in Mg-9Gd-xAl alloys. The results indicate that the lamellar phase consists of three elements, Mg, Al, and Gd, and the atomic ratio is close to 1:1:1. It was identified that the lamellar phase is (Mg, Al)2Gd phase which has the same crystal structure with Al2Gd. In addition, the lamellar phases were parallel to each other inside one grain, but the alignment directions inside the adjacent grains were different, which provide strong second phase strengthening effect. After solution treatment, the ultimate tensile strength of Mg-9Gd-0.6Al alloy with abundant lamellar phase is greatly improved to 193 MPa.

In this work, the microstructure and mechanical properties of Mg–Al–Ca–Mn alloys with different Ca/Al ratios (0.2, 0.6 and 1.0) have been investigated. The results showed that with the increase of the Ca/Al ratios, the grain sizes of the alloys were significantly refined, and the morphologies and types of main second phases changed from a block Mg17Al12 phase to a semi-continuous Al2Ca (C15) phase and a continuous network (Mg, Al)2Ca (C36) phase. The extruded Mg–2.4Al–2.4Ca–0.6Mn alloy, which was consisted of dynamically recrystallized grains and undynamically recrystallized regions, possessed outstanding mechanical properties with the yield strength of 335.9 MPa, the ultimate tensile strength of 354.7 MPa and the elongation of 8.4%. This was mainly due to the resultant effects of grain refinement strengthening, secondary phases strengthening, texture strengthening and work hardening.

Magnesium matrix composites synergistically reinforced by SiC nanoparticles and second phases were prepared by 12 passes of multi-pass forging, varying the temperature. The effects of grain refinement and the precipitates on the hot deformation behavior were analyzed. Deformation zones which could be observed in the fine-grained nanocomposite before hot compression disappeared, and the trend of streamlined distribution for the precipitated phases was weakened. At the same compression rate, as the compression temperature increased, the number of precipitated phases decreased, and the grain size increased. For fine-grained nanocomposites, after the peak stress, there was no obvious dynamic softening stage on the stress–strain curve, and then the steady stage was quickly reached. The critical stress of the fine-grained nanocomposites was lower than that of the coarse-grained nanocomposites, which can be attributed to the large amounts of precipitates and significantly refined grains. The deformation mechanism of the coarse-grained nanocomposite was controlled by dislocation climb resulting from lattice diffusion, while the deformation mechanism for the fine-grained nanocomposite was dislocation climb resulting from grain boundary slip. The activation energy of the fine-grained nanocomposite was decreased, compared with the coarse-grained nanocomposite. The area of the workability region for the fine-grained nanocomposite was significantly larger than that of the coarse-grained nanocomposite, and there was no instability region at a low strain rate (0.001–0.01 s−1) under all deformation temperatures. The optimal workability region was 573 K /0.001–0.01 s−1 for the fine-grained nanocomposite, and the processing temperature was lower than the coarse-grained nanocomposite (623–673 K).

The hot deformation behavior and processing characteristics of AZ91 alloy and nano-SiCp/AZ91 composite were compared at temperature ranges of 523 K–673 K and strain rates of 0.001–1 s−1. Positive impact of SiC nanoparticles on pinning grain boundaries and inhibiting grain growth was not obvious when deformation temperature was below 623 K, but was remarkable when the temperature was above 623 K. By comparing compressive stress-strain curves of AZ91 alloy and nano-SiCp/AZ91 composites, the addition of nanoparticles could improve the deformation ability of a matrix alloy under high-temperature conditions. There was no essential difference of deformation mechanism between AZ91 alloy and the composite, but hot deformation activation energy of the composite was significantly lower than that of the AZ91 alloy. The AZ91 alloy and the composite had the same workability region of 600 K–673 K and 0.001–1 s−1, while instability region for the composite was reduced compared with that of AZ91 alloy at high temperature.

Mg–3Al–Zn alloy with the addition of Al and Si as a eutectic alloy was subjected to conventional hot rolling. The corresponding mechanical properties, microstructure evolution, and dynamic recrystallization mechanism were investigated by optical microscope, scanning electron microscope, electron backscattered diffraction (EBSD), and tensile tests. The experimental results indicated that the Mg–3(Al–Si)–Zn alloy had a microstructure refinement, thus rendering an enhanced mechanical properties in comparison with the Mg–3Al–Zn alloy. The refined Mg2Si particles could act as potential nucleation sites for recrystallization in as-rolled Mg–3(Al–Si)–Zn alloy sheets, which resulted in more completely recrystallized regions through particle stimulated nucleation and a weakened basal texture compared to Mg–3Al–Zn alloy. The improvement in the tensile strength of the as-rolled Mg–3(Al–Si)–Zn alloy can be attributed to grain refinement and second phase strengthening caused by the refined Mg2Si particles. [ABSTRACT FROM AUTHOR]

SiC nanoparticles reinforced magnesium matrix composite was fabricated by ultrasonic vibration assisted squeeze casting. Since ultrasonic device could meet the use requirements according to theoretic calculation, uniform dispersion of SiC nanoparticles was expected to achieve. The grains of the composite were refined compared with the AZ91 alloy, which was related to the increase of nucleation sites during solidification and Zenner pinning effect caused by SiC nanoparticles. With increasing the ultrasonic power, grain size of the composite changed no obviously while the morphology of β-Mg17Al12 phase was significantly affected. The ultimate tensile strength, yield strength, and elongation to fracture of the composites fabricated under different ultrasonic powers were simultaneously improved compared with the AZ91 alloy. The increase of yield strength could be attributed to Hall-Petch strengthening and Orowan strengthening for the present composites. Theoretical value of the yield strength obtained by the square root method was close to the experimental value. [ABSTRACT FROM AUTHOR]

A high-strength and good-ductility Mg93.83Zn1.5Dy4.5Zr0.17 (at%) alloy containing long-period stacking ordered (LPSO) phases was prepared by conventional casting, heat treatments and an equal channel angular pressing (ECAP) process. The microstructure evolution, especially the second phases (LPSO phases), and the mechanical properties of Mg93.83Zn1.5Dy4.5Zr0.17 alloy tailored by different treatments were investigated. The results showed that the microstructure of the as-cast alloy was composed of α-Mg matrix, block LPSO phases and eutectic phases. And, the latter two phases formed a continuous network structure in the vicinity of grain boundaries. After heat treatments, the eutectic phases in the vicinity of the grain boundaries all dissolved, while large amounts of block LPSO phases and lamellar phases were precipitated. The LPSO phases were refined obviously and a large number of kinks emerged after the ECAP treatment. The as-cast alloy exhibited ultimate tensile strength and elongation of 152MPa and 3.58% at room temperature, respectively. After a series of treatments, the ultimate tensile strength of the alloy was increased to 322MPa with elongation of 23.6%. [ABSTRACT FROM AUTHOR]