Combustion Synthesis of Ti3AlC2 Porous Skeleton with Spontaneous Infiltration by Aluminum Melt for Ti3AlC2-Al Cermet Preparation

This work shows the results of the application of the SHS process for the production of cermet Ti
3
AlC2-Al by a new method in two stages. At the first stage, SHS was applied to obtain a ceramic MAX phase Ti
3
AlC
2
in the form of a porous skeleton, which, in the hot state, with a short time delay (pause) of several seconds, was brought into contact with the Al melt at the second stage to carry out spontaneous high-temperature infiltration by this melt. The SHS of the Ti
3
AlC
2
phase was carried out from the initial pure powder elements titanium Ti, aluminum Al, and graphite C through the combustion of a stoichiometric mixture of powders inside a refractory crucible in an air environment with pouring the combustion product with aluminum melt. It has been found that the optimum pause after the combustion process and before pouring the melt is 7–8 seconds, which provides, on the one hand, the porous MAX phases structure formation completion from the starting reactants in the cooling skeleton, and on the other hand, the spontaneous infiltration of the melt into the pores. It is shown that, upon infiltration of pure Al melt, complete decomposition of the MAX-phase Ti
3
AlC
2
occurs with the fo rmation of TiC and TiAl
3
, but the presence of 12% Si, 5% or 32% Cu in the alloyed Al melt contributes to the partial retention of Ti
3
AlC
2
in SHS cermet. The phase composition of cermets infiltrated with pure Al is a TiAl
3
-TiC-Al composition, while cermets infiltrated with silicon or copper-doped aluminum alloys are Ti
3
AlC
2
-TiC-Ti
3
AlC
2
-Al and Ti
3
AlC
2
-TiC-CuAl
2
-Al compositions, respectively. The yield strength of SHS cermets obtained by infiltration with an A1-12 % Si melt exceeds that for a pure Al-12% Si alloy
$(\sim 260$
MPa) by approximately 58% and is
$\sim 410$
MPa.