Effect of starting composition on the synthesis of nanocrystalline TiC during milling of titanium and carbon

Abstract

Titanium and carbon powder mixtures with compositions of Ti 100− x C x ( x = 50, 40, 30) were milled under a helium atmosphere using a magneto ball mill. For Ti 50C 50 and Ti 60C 40 powder mixtures, nanocrystalline TiC was formed via a mechanically induced self-propagating reaction (MSR), indicated by an abrupt increase in the temperature of the milling vial that corresponded to the formation of TiC. The sudden temperature increase occurred after milling for approximately 70 h for Ti 50C 50 and after approximately 40 h for Ti 60C 40. No such abrupt temperature increase was detected when milling Ti 70C 30 and XRD analysis indicated that, for Ti 70C 30, the reaction to form TiC proceeded gradually as milling progressed. These results demonstrate that, for milling conditions that lead to the formation of TiC via MSR, a minimum carbon content is required to sustain the self-propagating reaction to form TiC, below which TiC is formed via a gradual reaction.