Analysis of microstructure and mechanical properties of alumina composites reinforced with Ti2AlN MAX phases

This study presents new findings on nitride MAX phases addition to ceramic matrix. Synthesised Ti ₂ AlN was incorporated into alumina matrix with the use of powder metallurgy. Due to the low thermal stability and tendency of MAX phases for decomposition, Spark Plasma Sintering (as rapid sintering method) was utilized for composites consolidation. In order to evaluate the possibility of adopting Ti ₂ AlN as reinforcing phase, the emphasis of the research was placed on microstructural analysis. Additionally, mechanical properties and tribological performance of produced sinters were examined. Successful synthesis of Ti ₂ AlN phase was confirmed by XRD and FTIR analysis. Moreover, performed observations revealed that MAX phase preserved it layered structure in prepared composites. In addition, obtained results showed an improvement in the mechanical properties within entire range of Ti ₂ AlN addition. Highest Vickers hardness (1974 HV) was measured for sinters with 2 and 2.5 wt% addition, while indentation fracture toughness reached maximum value of 4.84–5.13 MPa*m ^1/2 for shares in the range of 1.5–3 wt%. In case of composites with Ti ₂AlN content above 3 wt% decrease in mechanical properties was observed. For these sinters, adopted MAX phase undergoes phase transformation and reactions, resulting in presence of TiN, Ti ₂Al and Ti ₃AlN in microstructure. Additionally, composites with addition of 2, 2.5 and 5 wt% of Ti ₂AlN, when tested under the load of 60 N, where characterised by lower wear rate than reference pure alumina sinter.