Hydrogen trapping and micromechanical behavior in additively manufactured CoCrFeNi high-entropy alloy in as-built and pre-strained conditions

Abstract

The hydrogen trapping and micromechanical behaviors of additively manufactured CoCrFeNi high-entropy alloy (HEA) using the laser powder bed fusion (L-PBF) technique in the as-built and pre-strained states were explored through nanoindentation and micro-tensile experiments combined with thermal desorption analysis. To analyze the influence of pre-straining, both global pre-strains, imposed using the interrupted tensile tests, and local strain levels, estimated using the digital image correlation measurements, were employed. It was revealed that pre-straining (which increases the dislocation density in the alloy) does not enhance the hydrogen effects on the micromechanical performance of the L-PBF HEA. To understand this, rather unexpected, result, we investigated the trapping behavior of diffusional hydrogen in detail, through thermal desorption analysis combined with the Ag decoration technique. The results are discussed in terms of the hydrogen contents and trapping sites in the L-PBF HEA.