Synthesis and reaction path of Ti‐Al‐C MAX phases by reaction with Ti‐Al intermetallic compounds and TiC.

In this study, it was verified that the synthesis of Ti‐Al‐C MAX phases has advantages when using intermetallic compounds rather than using only elemental powders. The formation behavior of the MAX phases was presented through diffusion experiments. In the case of using elemental powder, Ti2AlC is produced at 1300°C, and Ti3AlC2 is produced at 1400°C. When intermetallic compounds are used, Ti2AlC is produced at 1000°C, and Ti3AlC2 is produced at 1300°C. In the case of the elemental powder, it is verified that Ti3AlC2 content is decreased and Ti2AlC is increased when heat treatment is performed at 1400°C for 3 h. Rather Ti3AlC2 content is increased when intermetallic compounds are used. When an intermetallic compound is used, synthesis occurs more actively at high temperatures, and the tendency to be thermally decomposed can be prevented. When TiAl and TiC are heat treated, Al of the intermetallic compound is diffused into TiC, and C of TiC is diffused into the intermetallic compound. Furthermore, there are many two‐dimensional defects in TiAl, which act as a C diffusion channel. C diffuses into TiAl to produce TiCX, and the MAX phases is generated by the short‐range diffusion of Al. At the region of TiC, TiC transforms into TiCX after C diffuses into TiAl, which consequently structure of TiC changes from cubic to hexagonal. This is the same crystal structure as the MAX phases, and it is confirmed that the (110) surface is maintained. A Ti‐C layer structure of the (110) surface is maintained, and it was determined that Al is diffused during this time to generate the MAX phases. [ABSTRACT FROM AUTHOR]