Raman spectroscopy as a tool to study TiC formation during controlled ball milling

Titanium and carbon elemental powder mixtures with compositions of Ti100-xCx (x=50,40,30) were milled under a helium atmosphere using a magnetoball mill. For Ti50C50 and Ti60C40 powder mixtures, the combined results of external mill temperature monitoring and x-ray diffraction (XRD) analysis indicated that, after a specific incubation period, titanium carbide (TiC) was formed rapidly via a highly exothermic mechanically induced reaction. However, contrary to the current understanding of mechanically induced self-propagating reactions, Raman spectroscopy clearly showed the formation of nonstoichiometric TiC in Ti50C50 and Ti60C40 powders prior to the sudden exothermic event occurring inside the mill. This result has not been reported in previous studies that used only XRD analysis to characterize the as-milled powders. It is now thought that a significant component of the heat generated after the incubation period may be due to a combination of rapid grain growth and/or recrystallization of the preexisting TiC, rather than the direct formation of TiC. When milling Ti70C30, the reaction to form TiC proceeded gradually as milling progressed. (C) 2005 American Institute of Physics.