Synthesis in hydride cycle of Ti–Al–C based MAX phases from mixtures of titanium carbohydrides and aluminum powders

Abstract

MAX phases are new type of easily machinable cermets, demanded in modern materials science as construction materials. One of the most widely studied and promising representatives of the titanium-based MAX phases are hexagonal Ti2AlC and Ti3AlC2. Current methods of their synthesis are unsuitable for their mass production. The creation and development of new methods and technologies for their producing are urgent tasks of materials science. The modern technologies are required providing high quality and productivity, cost-effective, environmentally friendly and easily scaled methods. In 2007, in our Laboratory of High-Temperature Synthesis of the IChPh of Armenian NAS, the Hydride Cycle method (HC) for synthesis of refractory alloys and intermetallic compounds was elaborated. The gist of this method is the use of the synthesized by Self-propagating High-temperature Synthesis mode (SHS) transition metal hydrides as starting materials. In the present work, for the first time, the HC method was applied in the synthesis of Ti2AlC and Ti3AlC2 MAX phases. Preliminarily, HCP TiC0.45H1.07÷1.17, FCC TiC0.5H0.22÷0.73 and TiC0.67H0.31-0.39 titanium carbohydrides were synthesized in the SHS mode and used as starting reagents. The present work was set to study the effect on the phase composition and structure of the synthesized MAX phases of conditions of HC. The analysis methods, used to certify the synthesized MAX phases, were: chemical, differential-thermal, X-ray phase. The microstructures of the samples were snapshot on SEM Prisma E scanning electron microscope. The work resulted in the synthesis in HC of single-phase Ti2AlC and Ti3AlC2 MAX phases with unit cell parameters [а = 3.0553; c = 13.6459; c/a = 4.466; P63/mmc] and [a = 3.0552; c = 18.7396; c/a = 6.132], respectively. This work demonstrated advantages of HC over the traditional methods of MAX phases synthesis.