Reactive synthesis and phase evolution of W2FeB2 alloy powders

Abstract

Using industrial FeB, tungsten powder, and amorphous boron powder as raw materials, W₂FeB₂ alloy powder was successfully prepared by reaction synthesis. The reaction mechanism was analyzed by comparing the phase compositions of the alloy powder at different temperatures and holding times. The crystal structure of the W₂FeB₂ phase in the alloy powder was studied, and the content of each phase in the powder was analyzed by the density of the alloy powder. The results showed that the density of the powder obtained at 1150 °C for 3 h reached 14.32 g cm⁻³, and the alloy powder was composed of 93.42wt% W₂FeB₂ phase with orthogonal structure and 6.58wt% W₂B phase. The reaction synthesis process involved the diffusion of B atoms and Fe atoms into the W matrix, firstly forming binary phases such as WB, W₂B, Fe₂B, W_xFe_y, and then generating ternary phases W_xFe_yB_z, and finally forming W₂FeB₂ phase. The powder morphology was optimized by plasma spheroidization, and the fluidity of the powders increased with the decrease of the powder feeding rate. The powder flow rate reached 19 s/50 g with a 3 g min⁻¹ powder feeding rate. Metastable phases such as (Fe_0.6W_2.8)B₄ and W_3.5Fe_2.5B₄ appeared after plasma spheroidization, but the phases could be eliminated with 1150 °C – 3 h annealing process.