Abstract
The characteristics of texture and microstructure of lean duplex stainless steels with low Ni content produced through hot rolling followed by annealing were investigated locally with electron backscatter diffraction and globally with neutron diffraction. Then, the ductile–brittle transition (DBT) behavior was studied by Charpy impact test. It is found that the DBT temperature (DBTT) is strongly affected by the direction of crack propagation, depending on crystallographic texture and microstructural morphology; the DBTT becomes extremely low in the case of fracture accompanying delamination. A high Ni duplex stainless steel examined for comparison, shows a lower DBTT compared with the lean steel in the same crack propagating direction. The obtained results were also discussed through comparing with those of cast duplex stainless steels reported previously (Takahashi et al., Tetsu-to-Hagané, 100(2014), 1150).
Highlights
Duplex stainless steels consisting of ferrite (α) and austenite (γ) have been widely used in corrosive environments [1]
These microstructures consist of α and γ phases, being similar to the cases of the previously reported cast steels the morphology and grain size of the α phase are significantly different from each other; both of the α and γ grains are elongated along the rolling direction (X-axis) with similar grain sizes, which are commonly observed for LNi and HNi
The texture, microstructural characteristics, and ductile–brittle transition (DBT) behavior in lean duplex stainless steels bearing low Ni content produced through hot rolling followed by annealing were studied
Summary
Duplex stainless steels consisting of ferrite (α) and austenite (γ) have been widely used in corrosive environments [1]. The duplex stainless steels exhibit ductile to brittle transition (DBT) behavior, despite γ phase fractures in a ductile manner even at a low temperature. The DBT temperature (DBTT) determined by Charpy impact test has been employed for primary evaluation of toughness. As has been reported by the present authors for cast duplex stainless steels [10,11,12], the DBTT obtained for specimens made from a keel block test sample is often different from that obtained for specimens prepared from a real large-scaled product itself, meaning that it is difficult exactly to evaluate the toughness for integrity insurance by a keel block casting method. AK CChoa. r(pTyakiamhpaagci,t Jtaepstaenr)mwahdeereby tesTtotkemyopKeroaktui rCeow, (aTsockoynotr,oJlalpedanu)swinagseuthseydl aflocrohthoel cimoopleadctwteisthtslaiqtuNidIDnAitrKogCeon. f(oTralkoawheargit,eJmappaenra)twurheesre thtaenstRTteamnpdeorialthueraetewdafsor choinghtreorllteedmpuesriantgureesth. yl alcohol cooled with liquid nitrogen for lower temperatures than RT and oil heated for higher temperatures
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