Combustion synthesis of NiAl/TiC composite from mechanically activated elemental powders

Abstract

The aim of this study was the synthesis of a homogenous distributed NiAl/TiC composite by combustion synthesis of elemental powders. The effect of the mechanical activation process was evaluated. The phase characterization and evaluation of the microstructure during milling and combustion synthesis were carried on by XRD and SEM-EDS and TEM-EDS, respectively. The XRD result of as-mixed powder compact after combustion synthesis showed that in addition to TiC0.75 and NiAl, some undesired phases like Ni3Al and Ni2Al­3 formed. While after combustion synthesis of 3h mechanically activated powder compact, only AlNi and TiC formed. The microstructural evaluations by SEM-EDS and TEM-EDS analysis confirmed the synthesis of truly homogenized NiAl/TiC composite. The mechanism of NiAl/TiC formation consists of dissolution of nickel, titanium, and graphite in molten aluminum and precipitation of TiC primarily and then the formation of NiAl. The value of microhardness of synthesized NiAl/TiC was 1070±12 HV. The main reason for this result is a uniform distribution of spherical TiC reinforcement in the NiAl matrix. Therefore, the mechanical activation process facilitated the reactions and improved the mechanical properties of the final composite.