Investigation of Ni nanocrystallization and the effect of Al 2O 3 addition by high-energy ball milling

Abstract

The effect of Al 2O 3 on synthesis of Ni nanocrystalline powder by high-energy ball milling has been investigated. Ni and Ni–10 wt.% Al 2O 3 powders were ball milled in an argon inert atmosphere. The milled powders were characterized by X-ray diffraction, scanning electron microscopy and microhardness measurements. The high-energy ball milling of Ni after 12 h resulted in crystalline size of about 48 nm, microhardness of 430 HV and particle size of 20 μm. Heat treatment of milled Ni powder showed an increase of lattice ordering degree and thermal stability. In milling of Ni–10 wt.% Al 2O 3, the adhesion of powders onto milling media was observed. The presence of 10 wt.% Al 2O 3 led to severe wear of vial, entrance of a large amount of Fe and formation of FeNi phase. The product of milling in this system was FeNi matrix nanocomposite which exhibited a high microhardness value of 810 HV.