激光合金化作用下的镁合金表-界面构效关系及腐蚀机理模型

Based on the key problem of interaction mechanism between micro interfacial structure and macro surface corrosion properties of laser surface alloyed magnesium alloys, researches on design and preparation of laser surface alloyed layer on magnesium alloys and its corrosion behavior and mechanism will be carried out in the present project. Effect of alloying elements on the microscopic interfacial structure, interfacial reaction rules and interfacial properties will be studied. Type, value and distribution of residual stress in the system after laser surface alloying will be investigated. The relationship between lattice microstructure and residual stress will be examined. The main reason for lattice distortion and lattice reconstruction on the surface of magnesium alloys will be clarified. The transformation process of complex interfacial structure during laser surface alloying process will be focused on. Effect of variation in micro interfacial structure and composition on macro corrosion resistance will be researched to clarify the relationship between interfacial microstructure and surface properties. The corrosion mechanism of magnesium alloys after laser surface alloying will be studied in depth and the life-extended model will be established. The project aims at enriching and developing the corrosion failure theory of magnesium alloys, and offering theoretical basis and technical support for the preparation of high corrosion resistant magnesium alloys.

本项目针对镁合金激光合金化层界面微观结构与表面宏观腐蚀性能之间相互作用机制的关键问题，开展镁合金表面激光合金化层的设计制备及其腐蚀行为和机理系统研究。考察微量元素的引入对微观界面结构、界面反应规律和界面性质的影响，研究激光合金化处理后体系残余应力的类型、大小和分布，分析晶格结构的改变与体系残余应力之间的关系，明确镁合金表层晶格畸变和晶格重构的主要原因。考察激光合金化过程中镁合金表层复杂微观界面结构的转变过程，研究微观界面结构和组成的改变对镁合金表面宏观耐腐蚀性能的影响，明确表-界面之间的构效关系。深入研究激光合金化作用下镁合金的腐蚀机理，建立其腐蚀延寿模型，丰富和发展镁合金的腐蚀失效理论，为高耐蚀性能镁合金材料的制备提供理论依据和技术支持。

腐蚀是制约镁合金广泛应用的关键问题之一。对镁合金进行激光表面熔凝/合金化处理，由于改变了其表/界面的微观结构、引入了残余应力及合金化元素，因而会对其腐蚀行为和失效机制产生重要影响。本项目针对镁合金表面激光熔凝/合金化层界面微观结构和组成对表面宏观耐腐蚀性能的作用机制问题，开展了激光熔凝/合金化层的设计制备及其腐蚀行为和机理研究。考察了激光作用类型、激光工艺参数对改性层体系内残余应力类型和大小的影响，研究了合金化组分的种类、含量、改性层微观结构（包括合金化组分与基体相结合界面的微观结构）与镁合金腐蚀行为之间的关系规律，揭示了激光熔凝/合金化层在NaCl水溶液和模拟体液两种介质中的腐蚀失效机理。本项目的实施取得的主要研究结果如下：①脉冲固体激光器相比连续波CO2气体激光器制备的激光改性层晶粒尺寸更为细小，热影响区范围较小，改性层表层引入的拉应力更大。在选定的工艺范围内，随着激光脉宽的增加拉应力呈现先减小后增大的趋势，而表面微孔数量逐渐增多。②激光熔凝层相比基材表面更粗糙，表面能更大，腐蚀降解速率较慢，因而激光熔凝处理后镁合金表面具有较好的细胞粘附性。③激光合金化层中添加ZrO2改善了镁合金的耐腐蚀性，而添加Zr、ZrB2反而加速了材料的腐蚀失效；添加TiO2-CeO2制备的激光合金化层腐蚀行为取决于二者之间的比例。④揭示了激光熔凝/合金化层的腐蚀失效过程和对基材的腐蚀防护机制。本项目的实施在丰富轻量化材料镁合金的表面腐蚀防护基础理论和腐蚀失效机制方面起到了重要作用，也为耐蚀性镁合金材料的设计制备提供了一定的理论指导。