Microstructural Characterizations of Maraging Steel Processed by Equal-channel Angular Pressing

摘要

Microstructures of a maraging steel subjected to equal-channel angular pressing (ECAP) up to 16 passes at room temperature were investigated.Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) examinations showed that the microstructures of the as-processed samples were characterized by a well-defined lamellar structure.With increasing the number of ECAP passes from 1 to 16,the lamellar spacing was significantly decreased from ～323 nm to ～54 nm,while the volume fraction of high-angle lamellar boundaries (HALBs,having the misorientation larger than 15o) was obviously increased form ～46％ to ～80％.The real lamellar-type nanostructured microstructures were completely accomplished in the tested steel after 8 or more ECAP passes.In addition,the grain refinement mechanism of maraging steel during the processing was discussed in detail.