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High density Ba 4 Sm 2 Fe 2 Nb 8 O 30 (BSFN) multiferroics ceramics with tetragonal tungsten bronze structure had been prepared by microwave sintering (MS) for 30min and conventional sintering (CS) methods for 4 h at 1275 °C. Single tungsten bronze phase and equiaxial grains are obtained for the MS BSFN ceramics, while a small amount secondary phase of SmNbO 4 is observed in the CS BSFN ceramics with columnar grains. Compared to Ba 4 Sm 2 Fe 2 Nb 8 O 30 ceramics prepared by CS method, enhanced dielectric, ferroelectric and magnetic properties are achieved for the MS BSFN ceramics. The values of electric polarization Pr and coercive electric field Ec are 2.11 μC/cm2 and 7.14 kV/cm for the MS BSFN ceramics, respectively. Meantime, the magnetic polarization Mr of 0.410emu/g and coercive magnetic field Hc of 2930Oe are also obtained for the MS BSFN ceramics. Based on the density, crystal structure, point defect and grain, the reasons of enhanced dielectric, ferroelectric and magnetic properties are discussed for the MS BSFN ceramics It is indicated that Ba 4 Sm 2 Fe 2 Nb 8 O 30 is an intrinsic room temperature multiferroic materials. [ABSTRACT FROM AUTHOR]

Direct energy deposition process based on laser and powder feeding provides powerful ability in integrated manufacturing of multi-materials components. In this work, TC11/Ti 2 AlNb dual alloy thin walls were prepared by direct energy deposition process. The microstructure evolution and tensile properties of the dual alloy samples perpendicular to the interface after different heat treatments were investigated. The results indicated that there were two distinct composition transition zones between these two alloys due to the dilution effect during the process. From TC11 alloy side to Ti 2 AlNb alloy side, the phase evolved as: α + β → α + α 2 + β/B2 + O → α 2 + β/B2 + O → α 2 + B2 + O. As-deposited materials presented better mechanical performance than other two counterparts both at room temperature and 650 °C elevated temperature. For all samples, the fracture positions were not located within the interface zone, indicating the good mechanical performance of the interface zone. For demonstration, a TC11/Ti 2 AlNb dual alloy blisk was prepared by this process. [ABSTRACT FROM AUTHOR]

In the present work, the size-dependent microstructure evolution of the Al-Zn-Mg-Cu alloy powders and the TiB 2 /Al-Zn-Mg-Cu composite powders are studied experimentally and theoretically. Several different types of microstructures are formed within alloy powders as a function of powder size but just one type is formed within the composite powders. The transitions in microstructure within a powder such as planar interface breaking down into cellular microstructure are also observed. The occurrence of the planar interface is analyzed in terms of critical undercooling and critical cooling rate, and the breaking down of planar interface is correlated with the thermal history of the droplets modeled by Newtonian thermokinetics and interface velocity modeled by BCT models. In the composite powders, the location of TiB 2 particles depends on the entrapment/pushing by the solid/liquid interface. The disturbance of temperature field and multiple nucleation sites due to the introduction of TiB 2 particles contribute to the variation in the microstructure of alloy powders and composite powders. Unlabelled Image • Featureless, cellular/dendrite microstructures are formed within the alloy powders. • The microstructure evolutions and transitions depend on the thermal history of the droplet. • The breaking down of planar interface is discussed from critical undercooling, cooling rate and interface velocity. • The non-planar solid/liquid interface and lower undercooling make the discrepancy of the location of nanoparticles. • The temperature disturbance and multiple nucleation events lead to equiaxed microstructure in the composite powders. [ABSTRACT FROM AUTHOR]

Abstract In this work, the microalloying approach was adopted to improve the mechanical properties of Mg-6Zn-0.5Zr alloy by co-addition of trace Cu and Ce elements. The results showed that the grain size of the Mg-6Zn-0.5Zr-0.5Cu-0.5Ce alloy was refined, and MgZnCu and Mg-Zn-Ce phases formed by the microalloying of Cu and Ce. In addition, high-density nano-scale precipitates were found in the matrix after extrusion. The alloy with Cu and Ce addition showed a basal texture with a stronger texture intensity. The yield strength, ultimate tensile strength and elongation of the as-extruded Mg-6Zn-0.5Zr-0.5Cu-0.5Ce alloy were 304 MPa, 345 MPa and 20.0%, respectively. This work demonstrated a close microstructure-strength relationship in which the refined grain size and abundant nano-scale precipitates led to an increase in the tensile yield strength of approximately 59 MPa compared with that of the Cu and Ce free alloy. Highlights • Abundant nano-scale precipitates formed in ZK60-0.5Cu-0.5Ce alloy during extrusion. • The Mg-Zn-Ce phase with an orthorhombic structure was confirmed in this study. • The as-ext ZK60-0.5Cu-0.5Ce alloy showed a strong basal texture. • The tensile yield strength increased of 59 MPa after the co-addition of Cu and Ce. [ABSTRACT FROM AUTHOR]

The Mg–4.50Zn–1.13Ca (wt%) alloy was subjected to double extrusion, and the microstructure and mechanical properties of the extruded alloys were investigated. Double extrusion refined the microstructure significantly, resulting in the enhancement of mechanical properties of the double-extruded alloys compared with the single-extruded alloy. The yield strength of the single-extruded alloy was 173MPa, while the value was increased to 320MPa and 370MPa after subsequent second extrusion at 300°C and 250°C, respectively. The second extrusion ratio had little effect on the microstructure and mechanical properties of the double-extruded alloys, while grain size was decreased and strength was increased with the decrease of double extrusion temperature. The double-extruded Mg–Zn–Ca alloy exhibited superior elevated temperature mechanical properties, which was attributed to the fine stable Ca2Mg6Zn3 intermetallic compound particles dispersed in the alloy. [ABSTRACT FROM AUTHOR]

Abstract: The Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt.%) alloy was hot rolled with different final rolling reductions at 400°C. The microstructure evolution and texture of the sheets were analyzed, and their effect on the mechanical properties was discussed. All of the rolled sheets consist of fine dynamically recrystallized grains with almost random orientation, large deformed grains with strong basal texture. In addition, bent lamellar-shaped long period stacking ordered (LPSO) phases due to kink deformation were observed in the deformed grains. The volume fraction of the dynamic recrystallization increased with increasing final rolling reduction and the basal texture weakened gradually. The strength of the alloy sheets changed a little with increasing final rolling reduction, while the yield anisotropy and the ductility were significantly improved. The sheet final-rolled with thickness reduction of 60% exhibits tensile yield strength of 306MPa, ultimate tensile strength of 393MPa and elongation to failure of 14.6% at ambient temperature, and tensile yield strength of 264MPa, ultimate tensile strength of 345MPa and elongation to failure of 19.4% at 250°C. [Copyright &y& Elsevier]