J.Q. Li

Dense pure binderless WC bulk material prepared by spark plasma sintering

The phases, microstructures and mechanical properties of binderless WC bulk materials prepared by the spark plasma sintering technique were investigated systematically. The addition of carbon was added to eliminate the impurity phase W2C. The relative density, Vickers hardness and grain size increase obviously with increasing sintering temperature, but increase weakly with increasing pressure or sintering time. The high relative density of 99·1%, HV30 of 27·5 GPa and fracture toughness KIC of 4·5 MPa m1/2 of pure binderless WC bulk with a grain size of 400 nm was obtained by sintering the WC powders with a particle size of 200 nm and the addition of 0·63 wt-%C at 1800°C for 6 min under 70 MPa.

Structural and magnetic properties of DyCo4―xFexGa compounds

The structural and magnetic properties of the DyCo 4− x Fe x Ga compounds with x =0, 0.5, 1, and 1.5 have been investigated by X-ray diffraction and magnetic measurements. Powder X-ray diffraction analysis reveals that each of the DyCo 4− x Fe x Ga compounds has a hexagonal CaCu 5 -type structure (space group P 6/ m m m ). The Fe solubility limit in DyCo 4− x Fe x Ga is x x , the larger the unit-cell parameters a , c , V , and the 3 d -sublattice moment but the smaller the 3 d uniaxial anisotropy. Magnetic measurements show that the Curie temperature of DyCo 4− x Fe x Ga increases from 498 K for x =0 to 530 K for x =1.5, the compensation temperature T comp decreases from 286 K for x =0 to 238 K for x =1.5, and the spin-reorientation transition temperature increases from 403 K for x =0 to 530 K for x =0.5. No spin-reorientation transition was found in the samples with x =1.0 and 1.5. The saturation magnetization of DyCo 4− x Fe x Ga measured at 173 K increases but the magnetization measured at 300 K decreases with increasing Fe content x .