Effect of Rare Earth Oxide Addition on the Microstructure and Properties of Ultrafine Grain W-20Cu Composites

Abstract

Ultrafine W-20wt%Cu (W-20Cu) powders doped with 0 wt%∼0.8 wt% rare earth oxides Ce_0.8Sm_0.2O_1.9 (SDC) were synthesized by the EDTA-citrate method using ammonium metatungstate and copper nitrate as raw materials, and the resultant powders were pressed and sintered at 1250 °C in H₂ atmosphere for 2 h to obtain SDC/W-20Cu composites. Morphology of the SDC/W-20Cu powders and microstructure of the sintered SDC/W-20Cu composites were observed by SEM, and density, physical and mechanical property of sintered SDC/W-20Cu composites were also tested to investigate the influence of rare earth addition. The results show that the SDC/W-20Cu powders are irregular in shape with particle size ranging from 100 nm to 200 nm. The addition of SDC has slight influence on the electrical conductivity, but obviously refines the grain size and improves the mechanical properties of the W-20Cu composites. The sintered SDC/W-20Cu samples have relative density above 97%. Bending strength and micro-hardness HV of the SDC/W-20Cu specimens are 1128 MPa and 3180 MPa with the addition of 0.6 wt% SDC, respectively, and the highest tensile strength reaches 580 MPa and 258 MPa at room temperature and 600°C, respectively.