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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60min,其材料致密度已达到96.4%。1420℃烧结90min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276.3kJ/mol减小到1420℃时的29.1kJ/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0.024μm3/min。
Ultrafine / nanocrystalline W-20Cu (mass fraction) composite powders were prepared by spray drying-hydrogen reduction method. The powder compact was directly pushed out into the high temperature zone from room temperature and sintered directly for water quenching. The densification and Microstructure changes. The results show that the ultrafine / nanocrystalline W-20Cu powders densify rapidly when sintered at 1000-1200 ℃. Powder compact sintered at 1200 ℃ for 60min, the material density has reached 96.4%. 1420 ℃ 90min sintering time to achieve more than 99% density. The sintering densification activation energy at 1100 ~ 1420 ℃ decreases continuously from 276.3kJ / mol at 1100 ℃ to 29.1kJ / mol at 1420 ℃. When the temperature is lower than 1200 ℃, W grain growth is not obvious, when the temperature exceeds 1300 ℃, W grain began to significantly grow. With increasing temperature, the grain size of spherulites is significantly spheroidized. At 1420 ℃, the grain size grows up to the Ostwald mechanism with G3 = kt. At this time, the kinetic coefficient K of grain growth is only 0.024μm3 / min.