Ying Chun Wang

Effect of Composition on Microstructure and Dynamic Mechanical Properties of W-Ni-Cu Alloys

The effects of tungsten contents (80-88wt.%) and different Ni:Cu ratio (7:3-3:7 by weight) on microstructure and dynamic mechanical properties of W-Ni-Cu alloys were investigated. Results show that at the same sintering conditions, with tungsten content increasing from 80 wt % to 88 wt %, tungsten grains increase slightly. Spherical and more uniform tungsten grains distribute in matrix phase in 85W alloys with Ni:Cu ratio of 1:1 than that of 3:7 and 7:3. The results also show that the dynamic yield strength of W-Ni-Cu alloys goes up with tungsten content increasing, but keep similar deformation capability. With strain rate increasing in the range of 2600-4200s-1, 85W displays strain rate softening effect. Adiabatic shear bands are formed at strain rate over 3200s-1.

Effect of Austenizing Temperature on Microstructures and Mechanical Properties of Cr-W-Ni-Alloy Steel

An investigation was made to determine the effect of austenizing temperature on microstructure and tensile properties of Cr-W-Ni-alloy steel. Correlations of microstructure tensile properties and austenizing temperature parameters were established. Analysis of optical and scanning electron microscope show that there were a lot of coarse spherical undissolved carbides dispersed on the lath martensitic matrix in as-quenched specimens when austenized at 900°C while there were only very little nanometer carbides when austenized at 1000°C and 1100°C. The tensile properties show that austenizing temperature had large effect on the mechanical property of the Cr-W-Ni-alloy steel. Oil quenching after austenized at 1100°C for 26 minutes followed with tempering at 260°C for 3h, Cr-W-Ni-alloy steel obtained best strength and ductility match.