Effect of Microstructure on Fracture Mechanisms in Galvannealed Coatings
Effect of Microstructure on Fracture Mechanisms in Galvannealed Coatings
复制标题
微观结构对合金化镀锌层断裂机制的影响
DOI：
10.2355/isijinternational.40.172
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发表时间：
2000
影响因子：
1.8
通讯作者：
J. Inagaki
中科院分区：
文献类型：
--
作者：
A. Alpas;J. Inagaki
通过对镀锌钛稳定无间隙低碳钢和铝镇静低碳钢进行拉延珠试验和扫描电子显微镜观察涂层组织，研究了镀锌层的断裂机理。在实验室感应炉中，对采用工业热镀锌工艺的镀锌样品进行了450、500和550°C的渗锌处理，处理时间为1至360℃。在Fe含量较低(5g/m2以下)的涂层中，拉延珠试验中的粉碎量最小。在δ-1相中形核的裂纹在钢-涂层界面上停止了扩展，在那里只发生了有限数量的脱粘。当Fe含量在6~9g/m2之间时，涂层的粉化量急剧增加。在这些涂层中，源于δ1相的裂纹到达Γ-Γ1-δ1相界，这提供了优先的裂纹扩展路径，从而促进了涂层内的断裂。提出了一个考虑镀锌层抗粉化性能的断裂力学模型。
Fracture mechanisms in galvannealed coatings have been studied by performing draw bead tests on galvannealed Ti stabilized interstitial free and Aluminum killed low carbon steel sheets and by investigating coating microstructures by scanning electron microscopy. Galvannealing treatments, on samples galvanized using an industrial hot-dip galvanizing process, were conducted at 450, 500 and 550°C for several time periods between 1 and 360 s in a laboratory induction furnace. In the coatings with low Fe content (up to 5 g/m 2 ), the amount of powdering during the draw bead test was minimal. Growth of cracks nucleated within the δ 1 phase was arrested at the steel-coating interfaces where only a limited amount of decohesion occurred. A steep increase in the amount of powdering was observed in coatings with Fe contents between 6-9 g/m 2 . In these coatings, cracks originating from the δ 1 phase reached Γ-Γ 1 -δ 1 phase boundaries, which provided preferential crack growth paths and thus facilitated fracture within the coating. A fracture mechanics model was proposed to account for the powdering resistance of galvannealed coatings.