Conferences

Cocrystallization of MAX-Phases in the Ti–Al–C System

  
V.T.Witusiewicz,
 
U.Hecht,
 
B.Hallstedt,
    

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2015, #07/08
http://www.materials.kiev.ua/article/1977

Abstract

The structure and phase transformations in the Ti–Al–C system were studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy, including energy-dispersive X-ray spectroscopy and electron back-scatter diffraction on samples obtained by arc melting and annealing at high temperatures. It is shown that the ternary system has a cocrystallization region for both MAX-phases, N and H. The Ti41.5Al38.5C20 samples contain three phases at all experimental temperatures (from 650 to 1660 °C): Ti3AlC2 (N-phase of Ti3SiC2 crystal structure type), Ti2AlC (H, Cr2AlC type), and binary intermetallic TiAl3 (ε, its own crystal structure type). The morphology in the as-cast alloy and annealed samples (at temperatures above and below the solidus temperature, 1660 and 1250 °C, respectively) shows that invariant solidification at 1405 °C (solidus temperature) precedes the univariant simultaneous solidification of N- and H-phases, both MAX-phases separating from the melt.


AL–TI–C SYSTEM, MAX-PHASES, SOLIDUS, TI2ALC, TI3ALC2