抄録
Fe-Mn alloys have similar microstructure to Fe-Ni alloys in iron rich region, therefore they have promising potential as structural materials at cryogenic temperatures. Fe-Mn alloys, however, lose their toughness by catastrophic intergranular failure when tested at low temperatures. This is attributed to the segregation of impurities to grain boundaries. The segregation can take place at higher temperatures than 600°C, in both austenite(γ) and two phase(χ+γ) region.
An addition of molybdenum has been found to be effective in reducing the segregation of phosphorus in the two phase region and enhances toughness. However, no perceivable difference was observed in the segregation in the γ field.
Double temper has been also identified as a beneficial treatment for improving toughness, which promoted the reversion of austenite along grain boundaries and reduced the susceptibility to intergranular failure.
As a result it was shown that fairly good toughness could be achieved in Fe-6Mn-0.2Mo-0.05C alloy with QLT(800°C/1h/W.Q./700°C/1h/W.Q./600°C/1h.W.Q.) treatment.
