Katsuhiko Takahashi*, Minoru Asada** and Masahiro Kawakami*
* Faculty of Engineering, Toyohashi University of Technology, Toyohashi 441-8580 ** Department of Ecomaterials Engineering, Toyama National College of Technology, Toyama 939-8630The microstructure of Ni reduced from (Ni, Mg)O was observed, and then the effects of MgO content and temperature on sintering characteristics of the reduced Ni powder were investigated. The results were summarized as follows.
The fine MgO particles were uniformly dispersed in the reduced nickel. The diameters were 10-50 nm.
The porosity of sintered Ni was increased with an increase in MgO content at 1273-1573 K. The sintering temperature of more than 1473 K was required for Ni containing MgO to remarkably decrease the porosity. The porosity decreased linearly as a logarithmic function of time. The grain growth of Ni was expressed by a 1/3 power function of time.
Consequently, the smallest porosity of sintered Ni containing MgO was obtained at 1573 K, and then its hardness increased with increasing MgO content and sintering temperature.
It was obvious by observing the microstructure that the sintering behavior showed an intermediate stage. The sintering mechanism was discussed by assuming the vacancy volume diffusion.
solid solution, reduction, oxide particle dispersion strengthening nickel, sintering, porosity, grain growth, diffusivity