Ti2AlC triggered in-situ ultrafine TiC/Inconel 718 composites: Microstructure and enhanced properties

Abstract

In situ ultrafine TiC dispersion reinforced Inconel 718 alloy with enhanced mechanical properties was fabricated by the technique of reactive hot-press sintering Ti2AlC and In718 powders. The effect of Ti2AlC precursor additions (5 vol.%, 10 vol.%, 15 vol.%) on microstructure and mechanical properties of TiC/In718 composites were investigated. A relationship of microstructural characteristics, room and elevated temperature mechanical performance, and underlying strengthening mechanisms were analyzed. The results show that initial Ti2AlC precursor transformed completely into ultrafine TiC particulate (∼230 nm) and distributed uniformly in the matrix after sintering 5 and 10 vol.% Ti2AlC/In718. However, TiC particulates tended to aggregate to stripes with the addition of Ti2AlC up to 15 vol.%, which, in adverse, weaken the properties of In718. The 5 vol.% Ti2AlC/In718 sample showed a higher tensile strength of 1404 ± 13 MPa with a noticeable elongation of 9.8% at room temperature compared to the pure In718 (ultimate tensile strength (UTS) = 1310 MPa, elongation = 21.5%). At 600 °C, 700 °C, 800 °C and 900 °C, tensile strength of the as-sintered 5 vol.% Ti2AlC/In718 composite was determined to be 1333 ± 13 MPa, 1010 ± 10 MPa, 685 ± 25 MPa and 276 ± 3 MPa, increased by 9.2%, 14.6%,14.2% and 55%, respectively, compared with that of monolithic In718 alloy. The excellent tensile properties of TiC/In718 composite can be ascribed to the combined mechanisms in term of increased dislocation density, dispersive Orowan and load transfer mechanisms.