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Three kinds of high-performance as-extruded Mg-Gd-Zn-Zr alloys were successfully prepared by controlling Zn and Gd contents and atomic ratio. The microstructure, mechanical properties and corrosion resistance of the three alloys were studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD), electron backscattering diffraction (EBSD), tensile-compressive experiment and electrochemical experiment. The results showed that the coarse grains and continuous second phase of as-cast alloys were refined and broken after hot extrusion, and the main components were α-Mg, W–Mg 3 Gd 2 Zn 3 , I–Mg 3 Zn 6 Gd and MgZn 2 phases. The mechanical properties and corrosion resistance tests revealed that the as-extruded GZ22 alloy had the highest ultimate tensile strength (UTS) of 362 ± 6 MPa and the lowest corrosion rate of 0.94 mm/year, which was attributed to the fine grains and a small amount of dispersed second phase. The strength of as-extruded GZ56 alloy decreased due to excessive hard and brittle W-phase. Meanwhile, a large amount of second phase content made the alloy had the lowest corrosion resistance. In addition, the as-extruded GZ26 alloy with high Zn/Gd atomic ratio had good comprehensive mechanical properties, and its UTS and elongation (EL) were 332 ± 3 MPa and 24.5 ± 0.6%, respectively. The unique feature of this alloy was that weak texture intensity led to good tension-compression yield symmetry, and its corrosion resistance was second only to that of the as-extruded GZ22 alloy. [ABSTRACT FROM AUTHOR]

Mg-xAl alloys (x = 3–12 wt%) were prepared by high pressure solidification. The microstructure of the alloys was studied using Scanning Electron Microscope (SEM) and Electron Backscatter Diffraction (EBSD), and the strengthening mechanism was analyzed in combination with the compressive properties of the experimental alloys. Furthermore, the grain boundary segregation of Al solute was investigated by experiments and first-principles calculations. For the Mg-xAl alloys solidified under atmospheric pressure, the microstructure will be a single solid solution when the Al content of the alloy is less than 5 wt%. However, for the Mg-xAl alloys solidified under 4 GPa pressure, the microstructure will always ba e single solid solution when the Al content of the alloy is less than 12 wt%. Moreover, the segregation of Al solute with a high concentration gradient can be observed at plenty of grain boundaries (area fraction is as high as 46%), because α-Mg dendrites are significantly refined under high pressure. In addition, many Al atoms are dissolved in the α-Mg matrix owing to high pressure. On this basis, it is found that grain boundary segregation of Al solute can decrease the grain boundary energy, and increase the bonding strength of grain boundaries. As a result, the Mg–Al alloys solidified under high pressure have superior compression properties. The compression strength of the Mg–9%Al alloy and the Mg–12%Al alloy solidified under 4 GPa is as high as 458 MPa and 490 MPa respectively, the alloys retain superior plasticity simultaneously. [ABSTRACT FROM AUTHOR]

Slip/twinning activity and theoretical critical shear strengths (τ max) during room-temperature tensile deformation of as-extruded pure Mg and Mg-1wt.%Y sheets were investigated quantitatively via electron back-scattered diffraction (EBSD), scanning electron microscope (SEM) and first-principles calculation. Slip trace analysis results indicated the relative frequency of the active slip modes transformed from basal slip (100%) for pure Mg, to basal slip (84.8%), prismatic slip (9.7%) and pyramidal slip (5.5%) for the alloy. The proportion of grains containing twins reduced significantly from 20.5% to 5.92% with Y addition. To explain the mechanism for the enhancement of the non-basal slip activity in Mg–Y alloy, the critical resolved shear stress of basal slip and pyramidal II slip were assessed by calculating τ max. The calculated results showed that the τ max ratio of the pyramidal II slip to basal slip decreased from 13.7 to 7.5, which may be responsible for the observed enhanced activity of non-basal slip. [ABSTRACT FROM AUTHOR]