2014 年 100 巻 9 号 p. 1150-1157
Influence of casting conditions and chemical compositions on ductile-to-brittle transition (DBT) behavior in duplex stainless steels was studied. Cleavage fracture of ferrite grain causes DBT in spite of ductile fracture of austenite grans at low temperature. Most influential factors on DBT temperature (DBTT) is chemical compositions, ferrite volume fraction and purity of cast steel. Compared with forged steels with similar fracture unit, the present cast steels show much lower DBTT, which is attributed to dispersed austenite grains that hinder the cleavage crack initiation and propagation. By using a serial sectioning 3D method, a group of austenite grains with an identical variant observed with a conventional 2D method was revealed to be connected each other.
