Use of EBSD technique to examine microstructure and cracking in a bainitic steel

The material investigated is a 2.25Cr-1Mo low alloy steel widely used for the manufacture of components in the petrochemical and power generation industries. Backscatter electron imaging combined with EBSD mapping has made possible the investigation of the microstructure and crystallography of tempered bainite in steel. The spatial resolution in EBSD is approx1 mu m, allowing the orientation of individual bainite laths to be determined. Sheaves or packets of laths consist of bundles of parallel orientation. Packets are predominantly twin related. The unit crack path for cleavage fracture is identified as being the packet. Moreover it is probable that the cleavage plane within a packet is always a {001} plane.