疲劳裂纹在奥氏体/铁素体异种钢焊接接头中的扩展行为

采用三点弯曲试样研究了疲劳裂纹在奥氏体/铁素体异种钢焊接接头中的扩展行为与显微组织的关系，测得疲劳裂纹在Cr25Ni13/13CrMo44异种钢焊接接头中的扩展速率da/dN,并且讨论了疲劳裂纹扩展与显微组织之间的关系。实验结果表明，疲劳裂纹在异种钢焊接接头熔合区中扩展的路径，是接头中韧性最低的热影响区过热区，裂纹在铁素体材料侧，跟随熔合线并平行于熔合线5～25μm扩展，而马氏体层对疲劳裂纹有较大的抗力，疲劳裂纹的扩展路径主要受组织韧性的控制。疲劳裂纹在Cr25Ni13/13CrMo44异种钢接头的扩展速率为：da/dN=7.07×10-13(△K)3.863。

The Behavior of the Fatigue Crack Propagation in Austenitic/Ferritic Dissimilar Metal Joints

The E309 type austenitic electrodes was used in welding of13CrMo44 heat resisting steel to form a dissimilar metal joint． The notched three-point bend specimens (S/W=4) were prepared for the fatigue crack propagation (FCP) test． The relationship between the fatigue crack propagation and the microstructures in the joint was studied． The results show that the path that the fatigue crack propagation takes is in the overheated zone of HAZ, which may be attributed to the low toughness values in the zone． The fatigue crack propagates along the fusion zone at the region 5-25μm to the fusion line． The martensite layer has ability to resist the fatigue crack propagation,which indicates that the trace of FCP is mainly controlled by toughness of the structures． The expression for fatigue crack propagation rate in the fusion zone of the Cr25Ni13/13CrMo44 dissimilar metal joint by Paris equation is as follows:da/dN=7.07×10－13(△K)3.863