Phase transformation and strengthening of the gas-atomized FeCoCr NiMo 0.5 Al 1.3 high-entropy alloy powder during annealing
Heliyon(2024)
Abstract
Phase evolution and strengthening of the FeNiCoCrMo 0.5 Al 1.3 powder alloy produced via inert gas atomization and annealed in the temperature interval of 300 - 800 degrees C have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and microhardness testing. It was found that annealing at 300 - 600 degrees C leads to an increase of the element segregations between the several solid solutions with a rise of the lattice misfit ( epsilon) to 1.5 % and microhardness growth to 1070 HV. It was assumed that elastic stress caused by the element partitioning is the main strengthening mechanism: microhardness rises linearly with misfit rise with dHV/d epsilon = 43400 MPa. Sigma arises after the maximum elastic deformation (in 1.5 %) was reached. Formation of the dispersed coherent sigma phase in the annealing interval 600 - 800 degrees C results in the microhardness rise. Oxidation that began at 800 degrees C in 27 h is accompanied with FCC formation due to a depletion of the B2 in Al caused by Al 2 O 3 formation. Estimation of the activation energy of the initial stage of the solid solution decomposition gives a very low value in 0.65eV, apparently caused by the high concentration of quenched vacancies. The activation energy of sigma formation approximately coincides with the activation energy of self-diffusion in BCC metals (about 2.60 eV).
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Key words
High entropy alloys,Powder,Gas atomization,Annealing,Strengthening,Solid solution decomposition
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