Effect of solution treatment and aging on microstructure and properties of laser powder bed fused FeCoNi alloy

doi:10.13251/j.issn.0254-6051.2025.02.019

Abstract

Abstract: Effects of solution treatment and solution treatment+aging on microstructure and mechanical properties of the FeCoNi medium entropy alloy prepared by laser powder bed fusion were investigated. The results show that the microstructure of solution treated alloy is BCC single-phase structure, and during the solution process, the strip-shaped molten pool dissolves and the grains undergo recrystallization and coarsening. Granular Ni₃Fe phase precipitates at the grain boundaries and within the grains of the solution treated and aged alloy, and its content decreases with the increase of solution temperature. Solution treatment at 900 ℃ and aging at 470 ℃ refine the grain size of the alloy from 4.16 μm(solution treated) to 2.43 μm. During the solution treatment process, the disappearance of cellular structure and the release of residual stress result in a decrease in the hardness of the 900 ℃ solution treated alloy to 314 HV0.2 and a tensile strength of 709 MPa. After solution treatment and aging, Ni₃Fe intermetallic compounds precipitate from the matrix, which enhances the strength of the FeCoNi alloy. The hardness of FeCoNi alloy after solution treatment at 900 ℃ and aging at 470 ℃ is 508 HV0.2, and the tensile strength is 1238 MPa. The alloy strength is mainly contributed by precipitation strengthening and grain refinement strengthening. However, the accumulation of dislocations near the grain boundary precipitates can cause stress concentration, leading to a decrease in the plasticity of the FeCoNi medium entropy alloy.

Key words: FeCoNi medium entropy alloy, laser powder bed fusion, solution treatment and aging, microstructure, mechanical properties

CLC Number:

TG456.7

Ye Guochen, Xia Zhonghu. Effect of solution treatment and aging on microstructure and properties of laser powder bed fused FeCoNi alloy[J]. Heat Treatment of Metals, 2025, 50(2): 121-127.

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