钢材热浸镀用Zn-Al-Mg-Si镀层合金的相关系及其耐蚀性能

Hundreds of billions of dollars are used up each year due to the steel corrosion on the world. Alloying elements adding the coating alloys are an effective method to improve the corrosion resistance performance of steel material and prolong the service life.In this proposal, a set of self-consistent thermodynamic parameters of Zn-Al-Mg-Si and Zn-Al-Mg-Si-Fe systems will be carried out by the CALPHAD and the thermodynamic properties and the phase equilibrium relationship at the rich-Al corner and the rich-Zn corner in these systems will be determined by combining the experiments and theoretical calculation. Influence of kinetic factor for hot-dip process on the structures of alloy coating also will be considered. The mechanism of the influence of Mg on the property of the Zn-Al-Si coating material and the effect of the loss of Fe during hot-dip process will be investigated. We can determine the essential relationship between the phase composition and distribution and properties and select the composition with a potential good property under the condition for designing and developing materials. The microstructures of the steel matrix, intermetallics, alloy coating and the corrosion products will be studied in order to clarify the mechanism of corrosion resistance. The available achievements could provide the scientific guidance for exploitation of the hot-dip Zn-Al-Mg-Si alloy coating steel plates with a high quality.

全世界每年因钢铁腐蚀造成的直接经济损失高达数千亿美元，通过元素合金化提高热浸镀合金镀层钢铁构件的耐蚀性，延长其使用寿命，一直倍受国内外关注。本项目采用实验和计算相结合的方式来建立描述多元多相体系Zn-Al-Mg-Si和Zn-Al-Mg-Si-Fe的热力学模型及相应的数据库，确定出富Al 端和富Zn端的热力学性质与相平衡关系。同时考虑热浸镀过程动力学的限制性环节对镀层组织结构的影响，研究添加Mg到Zn-Al-Si镀液中的作用规律及Fe的熔损机制，确定出体系中关键相的组成、分布和组织与性能的内在关系，测定镀液的物理化学性质，优化出镀液成分，可选择一些我们认为性能较好的组成和条件进行镀液合金开发。通过研究Zn-Al-Mg-Si 合金镀层腐蚀过程中钢基体、中间合金层、镀层及腐蚀产物的微观结构，阐明其耐蚀机理，为开发耐蚀性更强的新型热浸镀Zn-Al-Mg-Si 合金镀层钢板提供科学依据和理论指导。

钢材的防腐处理有利于保护环境，减少资源浪费，并能带来巨大的经济价值。在钢材表面制备热浸镀镀层是一种常见的防腐手段。我国虽然是金属镀层钢生产大国，但十分缺乏具有独立知识产权的热浸镀金属镀层产品。本项目围绕Al–Zn–Mg–Si四元合金体系，通过实验和相图热力学优化获得了一套自洽的Al–Zn–Mg–Si热力学参数，运用相图计算和凝固模拟进行高铝含量镀层合金的成分设计。利用自制的半自动热浸镀设备，制备热浸镀Al–Zn–Si–Mg合金镀层。结合热力学相图，分析镀层的物相组织以及各相的析出过程。利用浸泡腐蚀加速试验和电化学测试技术，对比不同镀层的耐蚀性，从而研究合金镀层的腐蚀行为，并阐释镀层的耐蚀机理。另外，对镀层合金层的研究还发现形核位置、形核热力学驱动力和异相界面能是影响固液反应的三个关键因素。研究表明，在富Al体系的Al–Zn–Si合金液中添加1~4 wt.% Mg，镀层的腐蚀失重减少了63%~77%。本项目的研究结果完善了Al–Zn–Mg–Si四元合金体系热力学数据库，探索了一种高耐蚀的Al–Zn–Mg–Si合金镀层，并探明了镀层的耐蚀机理，还对金属固液反应机理提出了新的解释。