Abstract: By means of TEM technique the orientation relationships of cementite, precipitated from islands of granular bainite during tempering, with ferrite have been objerved. By calculating the eigenvalue and eigenvector of transformation matrix, Isaichev relationship has been analyzed. The results indicate that Isaichev relationship indeed is the sum of Kungumov-Sachs relationship and Pitsch relationship, so the viempoint that the cementite with Isaichev relationship precipitates from austenite, instead of ferrite,is confirmed. Moreoven the matrix calculation shows that three reported orientation relationships among austenite, ferrite and cementite in pearlitic transformation cannot be simultaneously valid.

Key words: orientation relationship, eigenvector cementite