Microstructure and crystallography of 20MnCr5 steel tempered at different conditions

The microstructure and crystallography of 20MnCr5 steel tempered at 180 °C for 2 h were examined by electron back scattered diffraction (EBSD) in a field-emission scanning electron microscope. The crystallographic features of martensite in a prior austenite grain area were studied by pole figures (PFs). Compared to the theoretical PFs calculated with Kurdjumow–Sachs (K–S) and Nishiyama–Wassermann (N–W) orientation relationships (ORs), it is shown that both of the ORs exist in the investigated specimens. Misorientations distribution and the result of transmission electron microscope analysis indicating that [011]/54.7° lath boundary existed in the microstructure also prove the coexistence of K–S and N–W ORs. When the steels were further tempered at 350 °C/20 min or 500 °C/20 min, the length of boundaries in equal areas decreased and the crystallographic features still fulfill the coexistence of K–S and N–W ORs.