Sintering behavior of ultrafineanocrystalline W/Cu composite powders synthesized by sol-spray drying and subsequent hydrogen reduction process

摘要

Ultrafine particle with nanocrystalline W-10 wt.%Cu and W-20 wt.%Cu composite powders were synthesized by sol-spray drying and hydrogen reduction processes. The sintering densification and microstructure evolution of these powders were investigated. The results showed that significant densification occurred at the sintering temperature ranging from 1000℃ to 1200℃, which was dependent on the copper content. For the W-20Cu compacts, 96.4% of the theoretical density could be realized when sintered at 1200℃ for 60min. Nevertheless, W-10Cu compacts could obtain only 90% of the theoretical density even though the sintering temperature was elevated to 1300℃ for 60min. This indicated that a low copper content was unfavorable for sintering densification of W-Cu powder. When the sintering temperature was further increased to 1420℃ and the holding time was prolonged to 90min, the relative density of the W-20Cu and W-10 Cu compacts reached 99.1%. In the range of 1100～1420℃, the activation energy of sintering densification for W-20Cu and W-10Cu decreased with increasing sintering temperature. There is no obvious grain growth when the sintering temperature was below 1200℃, whereas rapid grain coarsening occurred when the sintering temperature was above 1300℃, companying with obvious grain spheroidizing. In addition, the grain coarsening at 1420℃ was in good agreement with the Ostwald mechanism and the calculated kinetic coefficients of grain coarsening for W-10Cu and W-20Cu were about 0.067μm~3/min and 0.026μm~3/min, respectively.