Experimental study on Nb₃Cr₂Ti_0.9W_0.4Fe₆ high entropy alloys with high strength and good ductility by laser powder bed fusion

High entropy alloys (HEAs) have been widely used in aerospace complex parts due to their unique mechanical properties. HEAs with body-centered cubic (BCC) structure have high strength and low plasticity. Due to the synergistic effect of solid solution strengthening and lower electron concentration, high entropy alloys containing refractory elements tend to have considerable strength and plasticity. A novel high strength Nb₃Cr₂Ti_0.9W_0.4Fe₆ HEA was developed in this work. The spherical powders were prepared by the dual process of mechanical alloying and high temperature remelting spheroidization (DP) since such technology has combined effect of mechanical milling (plastic deformation) and temperature lifting (atomic diffusion) to achieve the composition homogenization. At the same time, the powder prepared by gas atomization (GA) method is compared, and the printed parts are compared under the same parameters of laser powder bed fusion (LPBF). The results indicate that DP-SLM has higher microhardness and wear resistance than GA-SLM. The yield strength (YS), ultimate tensile strength (UTS) and average elongation (ε) of the samples measured by DP-SLM were 953 MPa, 1159 MPa and 14.8 %, respectively. The average elongation (ε) is 25 % higher than GA-SLM. The hot compression test of Nb₃Cr₂Ti_0.9W_0.4Fe₆ was carried out with Gleeble-3800 thermal simulation machine. The thermal processing diagram of the alloy under different stress variables was drawn by establishing the thermal deformation constitutive equation. The DP-SLM material recovers when the deformation temperature is 1000 ℃ with deformation rate stays at 0.01 s⁻¹. Nb₃Cr₂Ti_0.9W_0.4Fe₆ alloy processed at 1050–1150°C and a strain rate of 0.005∼ 0.1 s⁻¹ shows high power dissipation efficiency (up to 37 %) and better dynamic recrystallization structure. Nb₃Cr₂Ti_0.9W_0.4Fe₆ can be considered widely used in the engine combustion chamber, guide, turbine blade and turbo disk four hot end components. The BCC-HEA containing refractory element can also realize the synergistic increase of strength and toughness through reasonable design.