Fe-Cr合金の塑性変形におよぼす固溶水素の効果

Abstract

The influence of hydrogen charging on the mechanical properties of several Fe-Cr alloys was examined in detail, in order to investigate some fundamental aspects of hydrogen embrittlement of iron and steel. The change in flow stress caused by electrolytic hydrogen charging was analysed with special attention to the role of an alloying element of chromium and compared with available data on hydrogen diffusion and internal friction. The results obtained are summarized as follows: (1) The fracture elongation of Fe-Cr alloys, containing up to 20 mass% chromium, was always decreased by the introduction of dissolved hydrogen. Such a hydrogen embrittlement became more pronounced with the increase in chromium content. (2) The flow stress of Fe-Cr alloys was always increased by the introduction of dissolved hydrogen. Such a lattice hardening was observed in all the alloys used but no softening was detected. (3) The lattice hardening due to dissolved hydrogen in these alloys became more remarkable with the increase in chromium content, but it was apparently independent of the other minor impurities in the alloys. There is therefore a close phenomenological relationship between hydrogen embrittlement and lattice hardening. (4) The lattice hardening can be explained in terms of the dislocation model adopted so far for the explanation of hydrogen diffusion and internal friction. The increase in flow stress can be expressed as Δσ≈6recEB⁄b, where c is the lattice concentration of dissolved hydrogen, EB the binding energy of hydrogen with dislocations, and re and b the effective radius and the Burgers vector of dislocations, respectively.