Effect of γ'-δ precipitates tailored by Ti3AlC2 on Inconel 718 composites: Microstructure evolution, enhanced properties and strengthening mechanism

The novel Ti3AlC2/Inconel 718 composites were fabricated by in-situ hot press reaction to improve the thermostability and strength of the In718 alloy. In this paper, the effect of Ti3AlC2 content on the microstructure and high-temperature properties of composites were investigated. Microstructures and mechanical properties were evaluated using scanning electron microscopy and tensile testing. The phase diagram and time-temperature-transformation curve of γ’-γ”-δ phases were simulated by JMatPro6.0 software. The results reveal that Ti3AlC2 has an obvious refining effect on Inconel 718 grain, and the dominant strengthening phase in composites is γ’ phase. The tensile results demonstrate that the addition of Ti3AlC2 to the Inconel 718 significantly improves the mechanical properties at elevated temperatures. The 15 vol% Ti3AlC2/Inconel 718 sample showed a higher tensile strength of 1241 ± 13 MPa with a noticeable elongation of 5.2 ± 0.4% at 650°C compared to the pure Inconel 718 (tensile strength = 852 ± 12 MPa, elongation = 7.9 ± 1.1%). At 750°C, 850°C and 900°C, the tensile strength of 15 vol% Ti3AlC2/Inconel 718 composite can reach 911 ± 11 MPa, 459 ± 15 MPa, 283 ± 10 MPa, increased by 35.2%, 61.1% and 68.5%, respectively. The superior strength of the Ti3AlC2/Inconel 718 composites is attributed to the dispersive second phases strengthening, grain refinement strengthening, and load transfer strengthening.