EMBRITTLEMENT OF AMORPHOUS FE40NI38MO4B18 ALLOY BY ELECTROLYTIC HYDROGEN

The effects of hydrogen on the tensile properties and fracture process es at room temperature were investigated. Specimens were tested at var ious strain rates in air or under different cathodic charging-current densities. The slopes of the stress-strain curves were essentially ide ntical for all the specimens, except that the fracture points varied u nder different test conditions. Macroscopically, hydrogen only affecte d the elastic deformation behavior, but microscopically, the embrittle ment was caused by the heterogeneous nucleation of localized plastic d eformation. The degree of hydrogen embrittlement increased as the char ging current increased or as the strain rate decreased. With the same charging current and time, longer dynamic charging resulted in more se vere embrittlement. Before fracture took place, the strength of the al loy could be completely restored if hydrogen had been removed. Hydroge n diffusivity and solubility were used to draw the time-dependent hydr ogen concentration profiles for the specimens under different charging conditions. The difference in the mechanical properties was correlate d with the hydrogen concentration within the specimen.