EBSP analysis of modified 9Cr-1Mo martensitic steel

In order to clarify the structure change of 9Cr-1Mo tempered martensitic st eel during the high temperature creep, the structures deformed were observe d by SEM-OIM and TEM method. It was found that initial block and packet structures were equi-axed. These structures were very stable during creep, but just before rupture changed to elongate grain. From an analysis of the grain boundary, Sigma3(rotation angle 70.5 degrees), near Sigma 11(rotation angle 50.5 degrees) and small a ngle(rotation angle 10 degrees) boundaries existed in the martensite. This result agrees with the result predicted with K-S orientation relationship. It was also found that the density of Sigma3 boundary or near Sigma 11 boun dary decreased during high temperature creep. But, it was found that the de nsity of Sigma3 boundary decreased, and that of near Sigma 11 and small ang le boundaries increased during the high temperature deformation. In initial structure, relative frequency of < 110 > common axis(Block boundary) is la rgest to compare with other axes. But, just before the rupture. relative fr equency of < 110 > (Block boundary) suddenly decreased and < 123 > and < 23 3 > (not Block or Packet boundaries) increased.