1989 Volume 53 Issue 5 Pages 502-511
This study is aimed at making clear the effect of Mn and Cr on the microstructure and toughness of an Fe-Cr-Mn alloy which is considered as one of the candidate alloys for reduced activation materials for the first wall application of the fusion reactor.
The microstructures of Fe-12%Cr-(5∼30)%Mn(mass%) alloys after solution treatment at 1373 K for 3.6 ks are markedly varied with Mn contents; α′(martensite)+δ(ferrite) in 5%Mn alloy, α′+δ+ε(martensite)+γ(austenite) in the 10%Mn alloy, α′+ε+γ in 15%Mn alloy, ε+γ in the 20%Mn alloy, and ε+γ+δ in the 25%Mn alloy, and γ+δ in the 30%Mn alloy. It is to be noted that the δ phase increases with increasing Mn content when the Fe-12%Cr alloy contains more than 25%Mn, which suggests that Mn plays the role of a ferrite former.
In Fe-15%Mn-Cr alloy, the δ phase is not observed in the range of Cr contents up to 12%, whereas it is markedly increased with the addition of 16%Cr. C, N and Ni are very helpful in forming the γ phase in these alloys as generally known in Fe-Cr-Ni alloys.
The toughness evaluated by the Charpy impact test at 273 K and room temperature is very low in the 5%Mn alloy which consists of the α′ and δ phases. It is, however, significantly improved by a small amount of the γ phase and increases with increase of γ phase stability.
