Microstructure Change during Creep Deformation of Modified 9Cr-1Mo Steel

摘要

The microstructure change of modified 9Cr-1Mo steel during creep deformation has been analyzed by SEM-EBSP (Electron Backscatter Pattern) and TEM -Kikuchi pattern techniques. Many grain boundaries with <110> and <111> common axes exist in the as tempered steel. The grain boundary with <110> and <111> common axes corresponds to the Block boundary in the lath martensitic structure. The types of Block boundary in this steel are ∑3, near ∑11 and small angle. The result agrees with the one predicted with K-S orientation relationship. For the steel ruptured at 938K under the stress of 72.3MPa, the density of gram boundaries with <110> and <111> common axes significantly decreases and width of Blocks increases. No change of misorientation of lath boundaries occurs during creep deformation. It is concluded that the microstructure change of modified 9Cr-1Mo steel during creep deformation is accompanied by change of orientation relationship of Block boundary and migration.