9CrSi钢下贝氏体／奥氏体界面位错研究

On the Lower-Bainite/Austenite Interfacial Dislocation of 9CrSi Steel

利用透射电子显微镜观察了９ＣｒＳｉ钢下贝氏体／奥氏体界面位错。结果表明。

We, at Northwestern Polytechnical University, have found that gaining a clearer,thoush still not a full, understanding of the mechanism underlying bainitic transformation has helped us to develop Chinese meta- bainitic steels that are useful in coal-mine machinery, etc. To our best knowledge, nothing has yet been found in the open literature concerning the interfaceal structure of lower- bainite/austenite, which is needed for gaining further understanding of the mechanism underlying bainitic transformation. We now intend to satisfy this need.Lower meta- bainite (lower- bainite/austenite) consists of lower- bainitic ferrite and retained austenite and thus it is convenient for studying the interfscial structure of bainite/ austenite. Fig. 1 shows that the lower meta- bainitic structure of 9CrSi steel contains no carbide.Fies. 2(a) and 2(b) show clearly the interfaceal dislocations in the austenite side of lower meta- bainite. But when difftaction vector g is 312 or 211, the dislocations disappear, as shown in Figs. 2 (c) and 2(d ). Consequently, according to the invisible criterion of dislocation, we can state that the Burgers vector b is parallel to [111]a. The true direction of the diSlocation line, the trace and the pole of habit plane are determined througth measurements with trace analysis. Fig 3 shows that the angle between the Burgers vector and the true direction of the dislocation line is about 20°. Consequently, the interfaceal dislocations are of mixed type. Comparing the interfacial dislocations with those of martensite, we can conclude that lower meta-bainite interface can glide conservatively. Thus the formation of lower meta-bainite possesses the shear properties of martensitic transformation.