高Crフェライト鋼の高温クリープ変形中の転位下部組織の挙動

概要

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The creep behaviour of martensitic 9% chromium steels and the steels alloyed with Mo and W was investigated at temperature of 600 to 650℃ under stress of 238 to 350 MPa. The results showed that the creep curves of these alloys were similar to those observed for martensitic 9-12% chromium steels. The minimum creep rate of ε^^._<min> for model steels alloyed with Mo and W was one order of magnitude lower than ε^^._<min> in base steel. Also the changes of strengthening factor can be described by the effect of solid solution of Mo and W. The observed substructure revealed that sub-boundaries with well-knitted dislocations were always formed and the subgrain size in steady state was inversely proportional to the applied stress. The subgrain size and the dislocation density within subgrains during creep decreased unequivocally with increasing strain, while the misorientation of subgrains increased monotonically with increasing strain. The rate of coarsening for the subgrains of these alloys, however, was dependent on the solute Mo and W and its concentration. It is suggested that creep of these alloys is controlled by the mobility of dislocations in the subgrains and sub-boundaries under the present experimental condition.
社団法人日本鉄鋼協会の論文