準安定オーステナイト系ステンレス鋼における加工誘起マルテンサイトの拡散型逆変態に及ぼす前加工の影響
1992 年 78 巻 1 号 p. 141-148
詳細
1992 年 78 巻 1 号 p. 141-148
Effect of prior deformation on the microstructure of diffusionally reversed austenite from lath martensite and the mechanical properties of the reversed austenite have been investigated in a metastable austenitic 18.08 mass% Cr-8.65% Ni steel by means of transmission electron microscopy and tensile test. The steel used transforms to almost full lath martensitic structure through 50% cold rolling. Further cold rolling changes the martensite microstructure from lath to cell.
The reversion occurs with two different processes, depending on prior microstructure. The austenite reversed from martensite lath structure are nucleated at the lath boundaries and grow along them. The morphology is platelike and looks like martensite lath structure. They gather to form austenite block, which is composed of austenite lath with the same crystallographic nature. On the other hand, the austenite reversed from martensite containing cell structure are fine equiaxed in shape and random in orientation.
The 0.2% proof stress of reversed austenite is higher with increasing deformation rate. This increase can be explainable in terms of a refinement of effective grain size. The effective grain size of austenite reversed from martensite lath structure corresponds to austenite block one. The effective grain size of equiaxed austenite is smaller than that of austenite block.
