| Fe-12% Mn alloy is chosen for this investigation due to its characteristic properties of high susceptibility of hydrogen embrittlement and of strain-induced phase transformation Specimens were heated at 1100℃ for 2 hours and either furnace cooled or water quenched. The results of the X-ray phase determination show that furnace cooled specimen (FC) is having ferrite phase (BCC) only while water quenched specimen (WQ) is observed to contain mostly unstable austenite phase (FCC). Hydrogen concentraton in the two specimens was same and linearly increased with charging time, however, above the concentration level of 15 ppm, WQ had more hydrogen than that of FC with same charging time. With same amount of hydrogen in the specimens, even though WQ showed strain-induced phase transformation, it was less embrittled by hydrogen than FC. When WQ had higher hydrogen concentration, the effect of hydrogen on the embrittlement was greater for WQ than for FC. Impact energy was also greatly reduced with hydrogen content for WQ while the impact property of FC was not influenced by hydrogen. All the experimental results strongly suggest that the phenomenon of hydrogen embrittlement of water quenched Fe-12% Mn alloy is associated with the strain-induced phase transformation along with the processes of the faster hydrogen diffusion in BCC and of forming moledular hydrogen gas pressure due to the excess hydrogen in the transformed BCC. |
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