Fabrication of aluminum–ceramic skeleton composites based on the Ti2AlC MAX phase by SHS compaction

Abstract

A one-stage manufacturing technology of aluminum-ceramic skeleton composites by combining the processes of self-propagating hightemperature synthesis (SHS) of a porous skeleton formed by the MAX phase of the Ti2AlC composition and its impregnation by the aluminum melt under the pressure (SHS compaction). A composition of the exothermic charge 2Ti + C + 22,5 wt % Al + 10 wt % TiH2, which provides the formation of a porous skeleton of the Ti2AlC phase without impurity phases by the SHS technology, is selected. It is shown that when impregnating the hot SHS skeleton with aluminum, new phases are formed such as the MAX phase (Ti3AlC2), titanium carbide (TiC), and titanium aluminide (Al3Ti). However, the content of the basic MAX phase remains high, and the ceramic component of the material consists of Ti2AlC by 76 %. When analyzing the microstructure, it is revealed that the composite has certain residual porosity after the impregnation and cooling. The influence of the impregnation pressure (q = 22, 28 and 35 MPa) on the distribution of the aluminum content over the height and radius of the diametral sample section is investigated experimentally. It is shown that the nonuniform Al distribution over the sample bulk is caused by the nonuniform pressure and temperature fields as well as different compactibility of hot inner and colder outer sample parts. The degree of compaction of characteristic zones is leveled as the impregnation pressure increases, and composition inhomogeneity over the sample bulk decreases. The difference of aluminum concentration over the sample bulk at q = 35 MPa does not exceed 5 %. By the hardness level (HB ≈ 150 kg/mm2), the SHS-compacted aluminum-ceramic skeleton composite based on the Ti2AlC MAX phase corresponds to high-strength Al–Zn–Mg–Cu aluminum alloys.