纳米Ni-Al_2O_3金属陶瓷粉末热压致密化过程

Hot pressing densification process for nano Ni-Al_2O_3 powders

采用粒径小于100nm,金属Ni包覆Al2O3得到的纳米Ni Al2O3化学包覆粉为原料,将Ni含量不同的几种纳米Ni Al2O3(粒径约为38nm)金属陶瓷复合粉末首先采取模压成形方式压制成直径为30mm的圆片,然后放在石墨模具中在热压机上进行热压,研究热压(HP)温度和Ni含量对致密化过程的影响。研究结果表明:当Ni含量为20%和热压温度为1400℃时,制品密度和显微硬度最高;在1400℃热压2h,Al2O3 Ni2O烧结体的相对密度最高,达到99.6%,Al2O3 Ni5的显微硬度HV达到1690.9kg/mm2;随着Ni含量的增加,制品硬度降低,当Ni含量超过20%时,硬度降低非常显著,Ni含量为50%时HV降至1316.7kg/mm2;烧结体中Ni颗粒均匀分布在基体中,且大部分位于三角晶界处,有效地阻止了Al2O3基体晶粒的长大。

The chemically coated nano Ni-Al_2O_3 composite powders with particle diameter about 38 nm containing different Ni content were pressed into discs of diameter 30 mm, and then hot-pressed in graphite mould in hot pressing (HP) instrument using high pure argon atmosphere as a protective atmosphere. The influences of hot pressing temperature and nickel content of the composite powders were investigated on densification. The results show that the biggest sintered density and micro hardness can be obtained when nickel content is 20% at hot pressing temperature (1 400 ℃.) When at 1 400 ℃ and sintering for 2 h, the relative density of Al_2O_3-Ni_2O compact is 99.6%, the micro hardness of Al_2O_3-Ni5 compact is 1 690.9 kg/mm^2 . With the increase of the nickel content, the micro hardness of composite powders decreases remarkably, and decreases to 1 316.7 kg/mm^2 when nickel content is 50%. Microstructure analysis show that the nickel phase is uniformly distributes in the matrix Al_2O_3 phase, and most of nickel particle exists in the angular boundary and thus refines the Al_2O_3 matrix grains.