The role of precipitation in hydrogen diffusivity and mechanical properties of a high entropy alloy
Sara Corrêa Marques, D.S. dos Santos
Abstract
In the present work, we investigate the interaction of hydrogen with the microstructure of the novel Fe 38 Mn 25 Ni 24 Co 5 Cr 2 Al 4 Ti 2 high entropy alloy (HEA), under annealed and aged conditions. For this purpose, hydrogen gas permeation tests, slow strain rate tests in previously hydrogen charged specimens and thermal desorption analyzes were carried out. Under both conditions, low hydrogen diffusivity values were calculated at room temperature, comparable to that of nickel-based superalloys . Hydrogen diffusion coefficient for the alloy under annealed condition can be expressed by D = 1.58 x 10 − 7 m 2 . s − 1 exp ( − 43.7 R T ) k J . m o l − 1 and, for the aged condition, by D = 1.25 x 10 − 7 m 2 . s − 1 exp ( − 41.9 R T ) k J . m o l − 1 . Furthermore, mechanical characterization and fracture surface analyzes demonstrate that the aging treatment improves the mechanical properties and does not impact the hydrogen embrittlement susceptibility of the alloy. Our findings contribute to the investigation of hydrogen embrittlement mechanism and provide data for the design of HEAs with suitable properties for structural applications in severe environments.