JZUS - Journal of Zhejiang University SCIENCE

Journal of Zhejiang University SCIENCE A 2016 Vol.17 No.1 P.65-75

Evaluation of the critical stress of anodized coating-AZ91D substrate using SEM in-situ technology

Author(s): Xi-shu Wang, Xing-wu Guo, Yuzo Nakamura, Hui-hui Yang, Pan Pan
Affiliation(s): 1Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China; more
Corresponding email(s): xshwang@tsinghua.edu.cn
Key Words: Magnesium alloy, Anodized coating, Material mechanics, Flexural stress, Cracking behavior

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Abstract: Experimental investigations of the micro cracking behavior of a coating-substrate structure were carried out in-situ with a scanning electron microscope (SEM). An anodized coating layer was deposited on an AZ91D substrate by the galvanize pulse method. Results indicated that the failure mechanism of the coating-substrate structure was due to a mismatch of micro deformation between the coating and substrate. The micro deformations induced by different failure models were cracking, spalling, or delamination. The failure models were validated using theoretical, experimental, and digital image correlation methods. The critical stress of failure can be evaluated by measuring the biaxial stress.

氧化涂层与基体临界失效应力的扫描电镜原位试验研究

目的：以典型的氧化涂层-AZ91D基体材料为背景，开展涂层-基体结构的损伤行为研究，在扫描电镜原位试验基础上定量地评价这种结构材料的临界弯曲失效应力值。
创新点：在Stoney方程基础上首次用试验方法定量地表征氧化涂层与镁铝合金基体材料的弯曲失效应力值；建立梁或板最大弯曲扰度与临界失效应力之间的关系，弥补Stoney方程中没有考虑二维效应及涂层材料特性引起的不足，使之更加适合工程中常见涂层-基体结构的损伤特点。
方法：将如图1所示的涂层-基体结构试件断面仔细抛光后置于扫描电镜的真空腔内；边加载边观察断面中损伤行为的变化，特别是界面附近的变形和开裂状态；比较所对应的加载点位移和载荷大小，并把其作为评价损伤行为的力学参数。
结论：本试验方法定量表征的涂层-基体结构临界弯曲失效应力值和失效位置与扫描电镜损伤演化图形的数字散斑分析结果一致，适合二维涂层-基体结构损伤应力的评价。

关键词：氧化涂层；弯曲应力；界面力学；扫描电镜原位观测技术

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