溶胶-喷雾干燥超细/纳米晶W-20Cu复合粉末的烧结行为

Sintering Behavior of Ultrafine/Nanocrystalline W-20Cu Composite Powders Synthesized by Sol-Spray Drying

摘要:

采用喷雾干燥-氢气还原法制备超细/纳米晶W-20Cu(质量分数, %)复合粉末，粉末压坯直接从室温推入高温区烧结不同时间后直接取出水淬，研究其烧结致密化和显微组织的变化。结果表明，超细/纳米晶W-20Cu粉末在1000 ~1200 ℃烧结时发生迅速致密化。粉末压坯在1200 ℃烧结60 min，其材料致密度已达到96.4%。1420 ℃烧结90 min时致密度达到99%以上。1100~1420 ℃烧结时其烧结致密化活化能不断减小，从1100 ℃时的276.3 kJ/mol减小到1420 ℃时的29.1 kJ/mol。当温度低于1200 ℃时，W晶粒长大不明显，当温度超过1300 ℃时，W晶粒开始有明显长大。随温度的升高W晶粒发生显著球形化，1420 ℃烧结时发现其晶粒长大符合G3=kt的Ostwald机制，此时晶粒长大动力学系数K仅为0.024 μm3/min

Abstract:

Ultrafine/nanocrystalline W-20Cu (mass fraction) composite powders were synthesized by sol-spray drying and subsequent hydrogen reduction process. The powders compacts were sintered at various sintering temperatures for different holding time and then were rapidly quenched in water. The sintering densification and microstructure evolution were investigated. The results show that significant densification occurs at the sintering temperature ranging from 1000 to 1200 oC and 96.4% theoretical density can be realized when sintered at 1200 oC for 60 min. When the sintering temperature is further elevated to 1420 oC and the holding time is 90 min, the relative density of the sintered compacts exceeds the level of 99%. In the range of 1100-1420 oC, the activation energy of sintering densification decreases with the sintering temperature increasing and the value decreases from 276.3 kJ/mol at 1100 oC to 29.1 kJ/mol at 1420 oC. There is no obvious grain growth during the sintering stage below 1200 oC, whereas the grain coarsening is very rapid when the sintering temperature is above 1300 oC. As the sintering temperature increasing, the tungsten grains become spherical. In addition, the grain coarsening at the temperature of 1420 oC is in good agreement with the Ostwald mechanism and the grain coarsening kinetic coefficient is 0.024 μm3/min