| Research Abstract |
High Mn-Cr austenitic steels are considered to be an important high temperature structural material from the point of view of fast induced radioactivity decay(FIRD) and non-magneticity. The objective of the present project is to make a fundmental research on the microstructure and mechanical properties of 12% Cr-15%Mn austenitic stainless steels for the development of FIRD amterial for the first wall structural materials of future fusion reactor and to compare these properties with those of the reference materials of JPCAs and JFMS,which are being investigated for the development of fusion reactor structural materials in Japan.
The effects of the alloying elements V,Ti, Ta etc. were investigated to determine the improvement of mechanical properties. Tiny precipitates of VN and Ti(C,N)raised the high-temperature strength considerably. Content of 0.1 to 0.2%C,however, formed very coarse precipitates of M_<23>C_6 type carbide on the grain boundaries, which deteriorated low temperature toughness inducing intergranular fracture. Addition of 0.2%N and more was very effective for the restraining of coarse carbide on grain boundaries and to improve creep-rupture ductility considerably. Furthermore, the most appropriate combination of V,Ti and Ta addition should be investigated.
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