In situ tailoring of precipitation behavior and improving mechanical properties of (Ti2AlC+Y2O3) reinforced TiAl alloy produced by directed energy deposition

A (Ti2AlC + Y2O3) synergistically reinforced Ti-48Al-2Cr-2Nb alloy was prepared by directed energy deposition with in situ tailoring of precipitate formation by induction preheating and thermal cycle. The influence of C and Y2O3 coaddition on the microstructure and high-temperature compressive properties was systematically investigated. The results indicated that Ti2AlC was formed by adding elemental C, and the Ti2AlC phase was mainly distributed in two forms: long rod-shaped Ti2AlC with a micron scale that distributed uniformly in the matrix, and lenticular Ti2AlC particles with nanometer size that distributed along the (alpha 2/gamma) lamellar interface. The Y2O3 particles were randomly distributed in the matrix. Columnar grains in vertical cross section along the building direction were completely eliminated by adding C and Y2O3. The high temperature compressive strength increased from 597 MPa to 758 MPa at 850 degrees C by adding C and Y2O3. Finally, the precipitation mechanism of nano-Ti2AlC was discussed in detail. This work provided a valuable reference for the preparation of highperformance TiAl alloys by in situ tailoring of the precipitates during the DED process.