The purity evolution of Ti3AlC2 MAX phase synthesized by mechanochemical route: The effect of Al content and high‐temperature annealing

This study explores the effects of excess Al and annealing at high temperature on the purity of Ti3AlC2 MAX phase synthesized by the mechanochemical route. In this regard, a constant stoichiometric ratio of Ti: Al: C = 3: 1: 2 along with three blends of nonstoichiometric ratios with excess Al (Ti: Al: C = 3: X: 2, X = 1.1, 1.2, and 1.5) were ball milled. Then, to examine the annealing at high‐temperature effects, the compacted ball‐milled powders were heated at 900 and 1200°C for 1 h. The phase identification revealed that 10 h of ball milling caused a reaction between the elemental powders, and Ti3AlC2 and TiC were formed. The mechanism of the reaction during the high‐energy ball milling process is assigned to a mechanically induced self‐propagating reaction. Addition of excess Al to primary powders caused to increase the purity of Ti3AlC2 significantly. Furthermore, annealing at high temperature leading to complete reactions of the ball‐milled powders and increased Ti3AlC2 purity. The maximum Ti3AlC2 content of 88% was obtained of initial powder of Ti: Al: C = 3: 1.2: 2 ratio after annealing at 1200°C. The Ti3AlC2 and TiC compounds were successfully synthesized after 10 h ball milling of elemental powders of Ti, Al, and C. The effects of excess Al and annealing at high temperature on the purity of Ti3AlC2 MAX phase synthesized by mechanochemical route were evaluated. Maximum Ti3AlC2 content of 88% was obtained from the initial powder of 3Ti/1.2Al/2C ratio and after annealing at 1200°C. The Ti3AlC2 cannot be obtained from 3Ti/1.5Al/2C ratio as starting mixture by MSR mechanism after 10 h ball milling process.