Investigation of the effect of electrolytic hydrogen charging on tensile-ductility loss in different Al-added low density steels

Abstract

The presentation investigated the hydrogen embrittlement of a Fe-8.3Mn- (9.5, 12) Al–1C (wt.%) low density steel, focusing on the influence of electrolytic hydrogen charging on tensile-ductility loss. We performed a tensile test after hydrogen charging at a low strain rate (9.5 × 10−6 s−1) to observe hydrogen-assisted cracking. The concentration of hydrogen was measured by thermal desorption spectroscopy and the fracture surface was evaluated by scanning electron microscope. Tensile test results have shown that the strength and elongation of the two kinds of steel after hydrogen charging both reduced, especially the elongation loss was more significant. For 12Al steel, the maximum tensile strength and elongation loss values were 74.22%, 67.73%, respectively. While for 9.5Al steel, the strength loss value was relatively small, the maximum loss value was 8.36%, and it reduced the maximum elongation loss of 26.02%. For the existence of κappa carbides and annealing twins in the tested steel, hydrogen preferentially concentrated on the grain boundaries and twins, leading to intergranular cracking, and the fracture mode changed from ductile fracture to quasi-cleavage fracture.