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The plastic anisotropy in terms of tensile mechanical property, Lankford coefficient (r), and microstructure evolution of as-extruded Mg-1Y (wt%) and Mg-5Y (wt%) sheets along the extrusion direction (ED), transverse direction (TD), and diagonal direction (DD) were investigated in detail at temperatures between 25 ℃ (RT) and 300 ℃. The sheets exhibited anisotropic deformation behavior at lower temperatures, and nearly isotropic for Mg-5Y at 300 ℃ in these three directions. For both sheets, the ultimate tensile strength anisotropy (UA) and elongation anisotropy (EA) was not sensitive to the temperature, while the yield strength anisotropy (YA) decreased significantly from 49.1% (Mg-1Y) and 40.2% (Mg-5Y) at RT to 7.2% and 2.7% at 300 ℃, respectively. The r values of Mg-1Y in all directions first increased from 0.66-1.4 (RT) to 0.81–1.98 (200 ℃) then decreased to 0.67–1.56 (300 ℃), while those of Mg-5Y decreased from 1.04-2.05 (RT) to 1.18–1.35 (300 ℃) with increasing temperature. Few twins were observed in Mg-5Y after tension at RT while large amounts of twins occurred in Mg-1Y. The huge reduction of twins and the weakened basal texture are believed to increase the r value from 0.66 (Mg-1Y) to 1.04 (Mg-5Y) at RT. At 300 ℃, dynamic recrystallized (DRX) grains appeared in Mg-1Y while only a few DRX grains showed up in the vicinity of grain boundaries in Mg-5Y, which may be closely related to grain boundary segregation of the yttrium atoms. [ABSTRACT FROM AUTHOR]

Mg-0.5Sn-(0, 0.3 wt%) Y alloys were obtained by casting with a metal mould, then extruded to acquire the as-extruded sheets. The microstructures, and mechanical properties of the alloys were studied. The results indicated that Sn 3 Y 5 particles generated after the addition of Y into the Mg–Sn alloys. This contributed to the presence of fine grains in the extruded Mg-0.5Sn-0.3Y sheets, the size of which decreased from ∼16 μm to ∼4 μm, accompanied by a significant improvement in the mechanical properties. Specifically, with Y addition, the ultimate tensile strength and elongation along the extrusion direction increased by 21% and 191%, respectively. The crystallographic matching relationships between Sn 3 Y 5 and Mg were established via an edge-to-edge matching model. The calculated results illustrated that Sn 3 Y 5 had small crystallographic misorientation with α-Mg, and served as the sites of heterogeneous nucleation for the Mg matrix, which led to grain refinement of Mg-0.5Sn-0.3Y sheets. Meanwhile, the diffraction patterns obtained by transmission electron microscopy along [0001] Mg // [11 2 ‾ 3 ‾ ] Sn3Y5 well agreed with the simulation results and validated the prediction. Furthermore, the macro-texture and work hardening behaviour of the extruded sheets implied that in the tensile test, the as-extruded Mg-0.5Sn-0.3Y sheets underwent both basal and prismatic < a > slips, while only the basal slip was observed in Mg-0.5Sn. As more slip systems were activated and more mobile dislocations could be formed, this in combination with the fine-grain strengthening effect, resulted in the large tensile elongation and high tensile strength of the Mg-0.5Sn-0.3Y sheets. Image 1 • The grain size decreased by ∼78% in Mg-0.5Sn sheet with Y addition. • Both the strength and ductility of Mg-0.5Sn-0.3Y sheet were enhanced. • Sn 3 Y 5 have small crystallographic misorientation with matrix, serving as the heterogeneous nucleation sites. • Mg-0.5Sn-0.3Y sheet experienced both basal and prismatic slip, while Mg-0.5Sn only endured basal slip. [ABSTRACT FROM AUTHOR]

In this work, the multi-scaled micron SiC and carbon nanotubes (CNTs) reinforced AZ61 matrix composites were successfully fabricated by powder metallurgy method followed by hot extrusion. The CNTs were adsorbed onto the surface of the micron SiC particles through hydrogen bonding caused by the groups functionalized on the surface of SiC particles (hydroxyl (-OH)) and CNTs (carboxyl (-COOH)), and then a shift speed ball milling was used to disperse the CNTs uniformly in the matrix. The microstructure characterization showed that this method could maintain the structural integrity of the CNTs, and the hybrid reinforcements could significantly refine the grain size of the matrix. In addition, the basal texture of the composites was weakened gradually as the content of the reinforcement increased. Microstructural investigation revealed that fine MgO formed by in-situ reaction between the oxygen groups and the magnesium matrix resulted in enhanced interfacial bonding. The ultra-high strength and good ductility (ultimate tensile strength: 412 MPa, yield strength: 345 MPa, and elongation: 8.0%) were achieved in the AZ61-5SiC-0.5CNTs composite. The significantly improved strength of the composites was mainly attributed to the synergistic influence of grain refinement, load transfer and increased dislocation density in the matrix due to thermal mismatch while the good ductility can mainly be attributed to the weakened basal texture. This work introduces a method of coupling a novel processing method with hybrid reinforcements approach to develop magnesium matrix composites with high strength and good ductility. [ABSTRACT FROM AUTHOR]