[en] The as-cast Mg-4Zn-2Gd-0.5Ca alloy mainly contained I phase and W phase, while the I phase dissolved into Mg substrate after homogenization treatment which improved the alloy’s corrosion resistance. After the application of multidirectional forging (MDF), the grains were refined obviously accompanied with the precipitation of I phase. With the increasing pass of MDF, both the size of dynamic recrystallized grains and the amount of precipitated I phase increased. The corrosion resistance of Mg-4Zn-2Gd-0.5Ca alloy became worse after 1 pass of MDF as compared with the as-homogenizated condition because of the precipitation of I phase. Neverthless, the corrosion resistance of the as-MDFed Mg-4Zn-2Gd-0.5Ca alloy deteriorated with the increasing pass of MDF. As compared with grain refinement, the precipitated I phase is thought to play a main role on the corrosion behavior of Mg-4Zn-0.5Ca alloy.

[en] The high-current pulsed electron beam (HCPEB) treatment with current density 6 J/cm² was applied on AZ91 Mg alloy to improve its corrosion resistance. Results showed that the net-like Mg₁₇Al₁₂ disappeared on the surface of AZ91 Mg alloy after irradiation by HCPEB, which was instead of supersaturated Al element on the surface. Nevertheless, the application of HCPEB also led to the formation of crater-like and groove-like structures as well as micro-cracks on the surface of AZ91 Mg alloy. After HCPEB treatment by 3, 5 and 10 pulses, the AZ91 Mg alloy exhibited better corrosion resistance. However, the increasing amount of micro-cracks reduced the anti-corrosive properties of AZ91 Mg alloy as the pulse increased to 20 and 30.

[en] Ti/Al/Mg/Al/Ti laminated composites were fabricated via hot-pressing at 350 °C, 400 °C and 450 °C successfully. The influences of interface morphology, diffusion zone, constraint effect on the mechanical properties were investigated. At Ti/Al interface, intermetallic compounds aren't found. Whereas, they form at Al/Mg interface. With the increasing temperature, the bonding strength of Al/Mg interface doesn't change linearly, and the maximum strength is obtained at 400 °C because of intermetallic compounds with appropriate thickness. With the increase of temperature, the hardness at both Ti/Al and Al/Mg interfaces increases owing to the solid solution and the intermetallic phases. Also, the ultimate tensile strength of LMCs increases with sacrificing the fracture elongation. The rule of mixture is used to predict the theoretical strength. It is found that the theoretical values are less than the measured, and the reasons may relate to interfaces in Ti/Al/Mg/Al/Ti laminated composites. (author)

[en] Particle reinforced magnesium matrix composite (PMMC) possesses the merits of high specific strength, high specific modulus, better dimensional stability, good wear resistance and lower production cost, which is thought as a promising material in the field of aerospace, automobile, electronic communication, etc. To eliminate the casting defect, the PMMC is usually experienced hot deformation process. The present paper mainly focuses on the deformation behavior of PMMCs. First, the development of PMMCs based on particle size is introduced. Then, the hot deformation technology and deformation mechanism of PMMCs at elevated temperature are given and analyzed, respectively. After reviewing the dynamic recrystallization and texture of PMMCs, its future development is suggested based on the current research progress.

[en] Highlights: • The Ti particles are elongated significantly in Ti_p/Mg–6Zn-0.2Ca composites along extrusion direction after hot extrusion. • The Ti_p/Mg–6Zn-0.2Ca composite exhibited a high yield strength of 383.6 MPa with an ultimate tensile strength of 404.8 MPa and a decent elongation to failure of 4.8%. • The strain hardening rate of Mg–6Zn-0.2Ca matrix increased by the addition of Ti particles. • Dislocation slip inside Ti particles plays an important role in the softening of Mg–6Zn-0.2Ca matrix during the process of plasitic deformation. Pure titanium particles reinforced Mg–6Zn-0.2Ca magnesium matrix composites were fabricated by semi-solid stirring casting followed by hot extrusion in this work. The microstructures and mechanical properties of the Mg–6Zn-0.2Ca alloy and its composites were studied. The Ti particles in as-extruded composites are significantly elongated along the extrusion direction. The average aspect ratio of Ti particles increases while the average size decreases, with the extrusion temperature decreasing. Ti particles promote the dynamic recrystallization of the matrix alloy, break the long-strip Ca₂Mg₆Zn₃ phases and refine the size of MgZn₂ phases in the Mg–6Zn-0.2Ca matrix, especially for low extrusion temperatures. The Ti_p/Mg–6Zn-0.2Ca composite extruded at 240 °C exhibited a high yield strength (YS) of 383.6 MPa with an ultimate tensile strength (UTS) of 404.8 MPa and a decent elongation to failure (EL) of 4.8%. The high strength is associated with fine grains, nano-precipitates as well as Ti particles. In addition, the work hardening rate of Ti_p/Mg–6Zn-0.2Ca composite is higher than that of Mg–6Zn-0.2Ca alloy at the early stage of plastic deformation due to the combined effects of the elongated Ti particles, the grain refinement and nano-scale MgZn₂ precipitates. However, the work hardening rate of the composite decreases faster owing to dislocations cross-slip. And the composite is easier to soften, which results from grain boundary sliding of fine grains and work hardening of deformable Ti particles.

[en] Highlights: • CaP coating were prepared on AZ91 alloy by pulse electrodeposition method. • Morphology and phase of CaP coatings were studied by thermodynamic analysis. • The most homogeneous pure HA was obtained with the duty cycle value of 0.10. • The coating deposited at the duty cycle of 0.10 has the best barrier properties. - Abstract: In present work, calcium phosphate coatings on AZ91 substrate were prepared by pulse electrodeposition at different duty cycle (0.05, 0.10, 0.15, 0.20) in the mixed solution of 0.1 M Ca(NO₃)₂ and 0.06 M NH₄H₂PO₄ at 60 °C. Phase composition and corrosion behavior of the as-deposited coatings were studied. Results showed that the calcium phosphate coatings had a grass-like structure. As the duty cycle increased, phase composition of the coatings changed from hydroxyapatite (HA) to mixture of HA and dicalcium phosphate dihydrate (DCPD). The adhesion of strength between the coatings and the substrate were higher than 10 MPa. Potentiodynamic polarization test and electrochemical impedance spectroscopy test in simulated body fluid (SBF) indicated that the samples deposited with calcium phosphate coatings exhibited better corrosion resistance as compared with the bare AZ91 alloy.

[en] In the present study, the Al 6061/Mg ZK60/Al 6061 composite sheets with the trapezoidal shaped intermediate layer were successfully obtained by multi-pass hot roll bonding. The microstructure and mechanical properties of the composite sheets under different rolling passes were investigated. The results demonstrated that the interface of the composite sheets achieved the strong interface metallurgy bonding, without discernible voids, cracks, and other defects. The introduction of the three-dimensional (3D) interface layer significantly improved the interface bond strength of the composite sheets. The interface layer composed of Al₃Mg₂ and Al₁₂Mg₁₇ was observed at the interface of the composite sheets. The thickness of the intermetallic compounds (IMCs) layer varied with the position of the interface, and the IMCs layer was the thinnest near the center of the sheet. The IMCs layer was continuously coarsening and fragmenting with the increase of rolling deformation, and stress concentration was easily generated at the interface between the Mg layer and the Al layer, so the crystal grains were more refined than that inside of the component sheets, which made the actual strength of the composite sheets higher than the theoretical strength. With the proceeding of the rolling process, the internal grain size of the component sheet gradually increased, and the interface products were coarsened and fragmented, which reduced the tensile properties of the composite sheets. The interface layer with moderate thickness and intact interface layer in the composite sheets appeared uniformly broken when it was under tensile stress, and the direction of microcracks generated was perpendicular to the tensile direction, which hindered the crack propagation and delayed the fracture of the composite materials and thereby enhanced the elongation of the composite sheets. Simultaneously, the trapezoidal shaped intermediate layer made the cracks deflect along the interface, which was conducive to the strengthening and toughening of the interface area, to improve the plasticity of the composite sheets.