Superior hydrogen embrittlement resistance of CoCrNi-based medium-entropy alloy via coherent precipitation and grain boundary strengthening

• Published in: Corrosion science 2024-11, Vol.240, p.112483, Article 112483
• Main Authors: Liu, Saiyu, Xu, Zhao, Zhu, Yujie, Shi, Rongjian, Gao, Kewei, Pang, Xiaolu
• Format: Article
• Language: English
• Subjects: Grain boundary strengthening; Hydrogen embrittlement; L12 precipitates; Medium-entropy alloy; Transgranular cracking
• ISSN: 0010-938X
• DOI: 10.1016/j.corsci.2024.112483

The strength and HE resistance of CoCrNi-based medium-entropy alloys were simultaneously improved via adding 264 at.ppm boron and the precipitation of nanoscale coherent L12 (γ'-type) particles. After aging treatment, the proportion of intergranular cracking decreased from 58.2 % in the solution-treated alloy to 27.6 %. Meanwhile, the yield strength increased by 102 %, and the ductility decreased by only 35.9 %. Notably, the elongation loss is only 9.4 %. On one hand, the added boron segregates to the grain boundaries (GBs), enhance the GB cohesive strength. On the other hand, precipitated L12 captures H, thereby reducing the concentration of diffusible H in the matrix and decelerating the diffusion rate of H. During plastic deformation, the L12 particles impedes the movement of dislocations and reduces stress concentration at GBs. This is associated with the presence of a completely coherent interface between the precipitated phase and face centered cubic matrix. This research provides insights into the beneficial effects of L12 phase precipitation and GB boron segregation on the HE resistance of M/HEAs. [Display omitted] •The hydrogen embrittlement mechanism of (CoCrNi)94Al3Ti3B0.03 HEA are revealed.•L12 particles trap hydrogen, reducing the diffusible hydrogen concentration.•L12 particles reduce the average free path of dislocations, decreasing dislocation accumulation at grain boundaries.•The segregation of boron at the grain boundary enhances grain boundary cohesive strength and reduces the diffusion rate of hydrogen along the grain boundary.