Effects of TiC nanoparticle additions on microstructure and mechanical properties of FeCrAl alloys prepared by directed energy deposition

Abstract

• Near fully dense TiC particles strengthened FeCrAl alloys have been fabricated by directed energy deposition. • TiC additions significantly refine the grain sizes and prompt columnar to equiaxed grain transition. • TiC particles strengthened FeCrAl alloys have good mechanical properties both at room temperature and high temperature of 650 ℃. Directed energy deposition (DED) additive manufacturing process has been attractive to the fabrications of FeCrAl alloys due to the advantage of near net shaping of complex shaped components. In order to improve the strength, TiC particles strengthened FeCrAl alloys have been fabricated by DED using blended FeCrAl powder and TiC nanoparticles. The results show that the TiC particles in the DED alloys have submicron sizes, and polygonal or dendritic shapes. Most TiC particles are distributed along the dendritic/grain boundaries. The additions of TiC particles effectively refine the grain sizes, and at the same time prompt a columnar to equiaxed transition of grains. The grain sizes are reduced from 1377 μm to 47 μm, 21 μm and 22 μm when the TiC particle contents in the DED alloys increase from 0 wt% to 0.7 wt%, 2.4 wt% and 3.5 wt%, respectively. The room temperature strength of the FeCrAl alloys increase with the increase of TiC particle content. With 3.5 wt% TiC particle content, the FeCrAl alloy has good mechanical properties with yield strength of 437 MPa, ultimate tensile strength of 688 MPa, and an elongation of 19 %. The 650 ℃ high temperature strength of the FeCrAl alloys first decrease and then increase with the increase of TiC particle content. With 3.5 wt% TiC particle content, the FeCrAl alloy has excellent mechanical properties with yield strength of 208 MPa, ultimate tensile strength of 223 MPa, and an elongation of 53 %. The present study provides an important basis for fabricating high strength particle-strengthened FeCrAl alloys using the DED process.