Synthesis and Characterization of a Nearly Single Bulk Ti2AlN MAX Phase Obtained from Ti/AlN Powder Mixture through Spark Plasma Sintering

Abstract

MAX phases are an advanced class of ceramics based on ternary carbides or nitrides that combine some of the ceramic and metallic properties, which make them potential candidate materials for many engineering applications under severe conditions. The present work reports the successful synthesis of nearly single bulk Ti2AlN MAX phase (>98% purity) through solid-state reaction and from a Ti and AlN powder mixture in a molar ratio of 2:1 as starting materials. The mixture of Ti and AlN powders was subjected to reactive spark plasma sintering (SPS) under 30 MPa at 1200 °C and 1300 °C for 10 min in a vacuum atmosphere. It was found that the massive formation of Al2O3 particles at the grain boundaries during sintering inhibits the development of the Ti2AlN MAX phase in the outer zone of the samples. The effect of sintering temperature on the microstructure and mechanical properties of the Ti2AlN MAX phase was investigated and discussed.

Study of the Influence of Sintering Atmosphere and Mechanical Activation on the Synthesis of Bulk Ti2AlN MAX Phase Obtained by Spark Plasma Sintering

“…For a better understanding, several micro-XRD analyses on different zones of the samples were performed and are marked with yellow numbers above the corresponding image. For the case of the MAX-1200, the presence of the Ti 4 AlN 3 (Position no.1, Figure 3 e) is confirmed, which is formed on the border of the sample, as we previously reported [ 28 ]. The formation of Ti 2 AlN by SPS of Ti and AlN powders has been previously described [ 25 ].…”

“…However, the presence of other crystalline phases presented under the XRD quantification sensibility cannot be excluded. It is noticeable that the MAX-1200 is the sample that gave the higher Ti 2 AlN MAX phase percentage (98 wt.%), and further information about its synthesis and characterization has been reported previously by focusing on the sintering temperature effects [ 28 ]. Some researchers once said that the Ti 2 AlN MAX phase obtained by the SPS method also turned out to be accompanied by secondary undesired phases, reaching up to 10 wt.%, which depended mainly on the consolidation parameters and starting powders [ 25 , 26 , 38 ].…”

“…This phase corresponds to the 413 MAX phase, and studies on it are scarce [ 38 , 39 ]. Previously, the formation of the Ti 4 AlN 3 on the Ti and AlN powder sintering by SPS has been attributed to the conditions that occurred only at the border of the sample [ 28 ]. Other previous studies explained the formation of the Ti 4 AlN 3 based on a transformation from a MAX phase of a low n order to a higher-order [ 40 ].…”

“…For the production of the Ti 2 AlN MAX phase, several powder metallurgy processes have been used, such as self-propagating high-temperature synthesis (SHS) [ 11 , 12 , 13 ], microwave sintering [ 14 ], hot pressing (HP) [ 15 , 16 , 17 , 18 , 19 , 20 ], hot isostatic pressing (HIP) [ 13 , 21 , 22 ], and spark plasma sintering (SPS) [ 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. The processing approach may be used depending on starting powder mixtures such as Ti+Al (milled in a nitrogen atmosphere), Ti+AlN, TiN+AlN, Ti+TiN+AlN, Ti+Al+TiN, under vacuum, argon, or nitrogen.…”

“…The mechanism of formation and the reaction sequences between 800 and 1450 °C that occur during synthesis by reactive SPS of Ti and AlN powder mixtures have been previously discussed. In previous work, the lower sintering temperature (1200 °C) at which we nearly achieved a single-phase bulk Ti 2 AlN MAX (>98% purity) starting from the Ti/AlN powder mixture and processed through reactive SPS was reported [ 28 ].…”