Microstructural and cold workability assessment of a new ODS ferritic steel

A new ODS composition (Fe-14Cr-2W-0.3Ti-0.3Y(2)O(3)) developed in the ExtreMat integrated Project has been produced by mechanical alloying techniques and consolidated by hot extrusion. This study summarizes some results of characterization and cold workability tests carried out at CEA and EPFL. It appears that the microstructure is fine and uniform after hot extrusion. According to microprobe analysis, solute elements are homogenously distributed in the matrix. However, the relatively high hardness level measured after hot extrusion and heat treatment may be detrimental in case of additional cold processing which is required to produce final shape like thin plates or cladding tubes. An assessment of the cold workability and the effect of the degree of cold work by rolling on recrystallisation temperature are addressed here. It is found that this material can be successfully cold rolled with a high degree of cold work (up to 60% of thickness reduction) without any damage. According to optical micrographs and Differential Scanning Calorimetry (DSC) measurements, it seems that the recrystallisation temperature remains always very high (above 1400 degrees C even though cold work level increases (up to 66% of thickness reduction). However, the hardness values begin to decrease for heat treatment temperatures above 1200 degrees C for hot worked conditions and below 1000 degrees C for cold worked conditions, respectively.