Structure and Properties of TixMo1–xCyNz Interstitial Alloys

Abstract

The study of the crystal structure and properties of multicomponent interstitial alloys helps obtain new materials with improved properties. In this paper, we report a study of the crystal structure and microhardness of bulk samples of Ti_xMo_1–xC_yN_z interstitial alloys differing in concentrations of their constituent elements. Samples were prepared by self-propagating high-temperature synthesis and homogenized by annealing at 2600 K for 8 h, followed by furnace-cooling. According to neutron diffraction data, the alloys have a face-centered cubic crystal structure in which the Ti and Mo atoms substitute for each other and occupy position 4b at random, and the C and N atoms also substitute for each other and occupy octahedral position 4a. Using X-ray diffraction data, we determined the crystallite size, dislocation density, and lattice strain in the alloys by the Rietveld method. The microhardness of the samples was determined by the Vickers method. The crystallite sizes determined by the Williamson–Hall method and using the Scherrer formula were found to differ significantly, but in both cases the crystallite size, dislocation density, and lattice strain increase with increasing component concentration in the composition of the alloys. With increasing carbon content, the crystallite size and lattice strain of the alloys decrease, whereas the dislocation density rises. With decreasing crystallite size and increasing dislocation density, the microhardness of the alloys shifts to higher carbon content. As the crystallite size and lattice strain decrease and the dislocation density rises in response to changes in the composition of the Ti_xMo_1–xC_yN_z alloys, their microhardness rises by a factor of 1.5–2 in comparison with binary titanium carbide and nitride. The present results can be helpful for application of interstitial alloys in tool making and high-temperature engineering.