D667不锈钢丝深加工过程中的断裂行为

Fracture behavior of D667 stainless steel wire in deep-processing

通过光学显微镜和扫描电镜对D667不锈钢丝断裂试样进行金相组织和断口形貌观察、夹杂物分析,探究断裂形成的原因。结果表明:D667原料试样金相组织为奥氏体,拉拔后在晶粒内部出现大量的交错滑移带,强度增加,韧性下降;D667不锈钢丝在服役过程中出现了脆性断裂和韧性断裂,断裂试样组织存在形变孪晶和针状马氏体等异常相;脆断试样中夹杂物尺寸较大且为钙基和铝基化合物,空洞择优在夹杂物附近形核,微裂纹形核后、迅速长大并连接诱导脆断。韧断试样中缩孔群尺寸较大,导致基体不连续,服役中向外扩展长大,形成韧断。

Metallographic microstructure, morphology of fracture and inclusions were observed by optical mi- croscopy and SEM to explore the formation of fracture. The results show that the microstructure of D667 raw material is austenite, cross slip bands are found after drawing and the yield strength and toughness reduced. Brittle and ductile fractures are observed due to the formation of the deformation twins and martensite phase during the steel wire serving. The inclusions of brittle fracture are calcium and aluminum compounds. Cavita- tion preferentially nucleates near the inclusions. Cracks rapidly grow up after nucleating and induce fracture. The size of porosities in ductile fracture is larger which leads to the matrix uncontinuous and then these porosi- ties expand in the following processing and finally induce ductile fracture.