F.C. Wang

Strength-improved Zr-based metallic glass/porous tungsten phase composite by hydrostatic extrusion

Hydrostatic extrusion, as a quite rarely applied technique, is used for the deformation of the Zr-based metallic glass/porous tungsten phase composite prepared by pressure infiltration. The fracture strength increases from 1852 MPa for the as-cast composite to 2112 MPa for the as-extruded composite. An apparent work hardening behavior was also observed in the as-extruded composite. The improved mechanical properties of the as-extruded composite are proposed to contribute to the stable interface between the metallic glass phase and the tungsten phase and the high dislocation density of the tungsten phase. (c) 2007 American Institute of Physics.

Dynamic Tensile Property of Zr-based Metallic Glass/Porous W Phase Composite

The dynamic tensile deformation and fracture behavior of the Zr-based metallic glass/porous W phase composite were investigated at room temperature by means of the Split Hopkinson Tension Bar (SHTB). It was found that the composite exhibited no appreciable macroscopic plastic deformation prior to catastrophic fracture and the fracture surface was perpendicular to the axial direction. Substantive micro cracks were observed along the interface between W grains or the interface between the metallic glass phase and the W phase. Scanning electron microscopy (SEM) observations revealed that vein-like patterns, dimple-like patterns and substantive ridge-like structures were the typical fracture morphologies on the fracture surface for the metallic glass phase and the morphology of the W phase is a mixture of intergranular and transgranular fracture. Based on those results referred above, the dynamic tensile deformation and fracture mechanism of the Zr-based metallic glass/porous W phase composite were discussed in detail.

Design, Preparation and Thermal Properties of (La0.4Sm0.5Yb0.1)2Zr2O7 Ceramic for Thermal Barrier Coatings

According to the theory of phonon transport and thermal expansion, a new complex rare-earth zirconate ceramic (La0.4Sm0.5Yb0.1)2Zr2O7, with low thermal conductivity and high thermal expansion coefficient, has been designed by doping proper ions at A sites. The complex rare-earth zirconate (La0.4Sm0.5Yb0.1)2Zr2O7 powder for thermal barrier coatings (TBCs) was synthesized by coprecipitation-calcination method. The phase, microstructure and thermal properties of the new material were investigated. The results revealed that single phase (La0.4Sm0.5Yb0.1)2Zr2O7 with pyrochlore structure was synthesized. The thermal conductivity and the thermal expansion coefficient of the designed complex rare-earth zirconate ceramic is about 1.3W/m•K and 10.5×10-6/K, respectively. These results imply that (La0.4Sm0.5Yb0.1)2Zr2O7 can be explored as the candidate material for the ceramic layer in TBCs system.