Mechanism-based characterization of the texture influence on the corrosion and corrosion fatigue properties of zinc-based wrought magnesium alloys

研究了挤压态含稀土和钙的镁锌合金在空气和腐蚀介质中循环载荷作用下的损伤机理。以前的工作的结果允许的结论，RE和Ca的挤压镁合金具有显着改善的性能的潜力，在疲劳载荷和应力腐蚀开裂（SCC）的条件下相比，含铝的镁标准合金。通过添加合适的合金元素和设定合适的挤压参数，将生产具有细晶粒尺寸和同时的织构弱化的镁合金，即通过改变变形机制，将组合诸如可成形性、增加的疲劳强度、增加的耐腐蚀性和减少的亚临界裂纹扩展的性能。应减少孪晶的形成，不仅通过弱的织构和细的晶粒尺寸，而且通过均匀的晶粒尺寸分布和合适的沉淀物，其减少孪晶的形成，同时不阻碍滑动过程。通过一方面提高疲劳强度，另一方面提高耐腐蚀性，目的还在于显著提高耐SCC性。不同的工艺参数和由此产生的微观结构的影响下，在空气中的循环载荷和应力腐蚀条件下的损伤机制进行了研究，和一个基本的工艺-微观结构-性能的关系是来自调查结果。通过关联的过程中的应力-应变的微观结构的变化，复杂的相互作用的纹理，所产生的各向异性，和拉伸-压缩的不对称性循环载荷下的腐蚀性介质的特征。对工艺-微观结构-性能关系的理解允许开发一组新的高性能挤压镁合金，并将知识转移到镁合金板材的疲劳和腐蚀行为，这形成了通过铸轧开发板材合金的基础。虽然该课题具有很高的科学和经济潜力，但尚未对其进行研究，也没有研究关于纹理对疲劳行为，特别是SCC的影响的现有损伤机制。

The proposal aims to investigate the damage mechanisms of RE- and Ca-containing extruded Mg-Zn alloys under cyclic loading in air and corrosive media. The results of previous work allow the conclusion that RE- and Ca-containing extruded Mg alloys have the potential of significantly improved properties under fatigue loading and stress corrosion cracking (SCC) conditions compared to the Al-containing Mg standard alloys. By adding suitable alloying elements and setting suitable extrusion parameters, Mg alloys with fine grain sizes and simultaneous texture weakening are to be produced, i.e. by changing the deformation mechanism, properties such as formability, increased fatigue strength, increased corrosion resistance and reduced subcritical crack propagation are to be combined. The formation of twins shall be reduced, not only by weak textures and fine grain sizes but also by homogeneous grain size distributions and suitable precipitates which reduce the formation of twins and at the same time do not hinder the slipping processes. By increasing the fatigue strength on the one hand and the corrosion resistance, on the other hand, the aim is also to achieve a significant improvement of the resistance to SCC. The different processing parameters and the resulting microstructure are to be investigated for their influence on the damage mechanisms under cyclic loading in air and under SCC conditions, and a fundamental process-microstructure-property relationship is to be derived from the findings. By correlating the course of the stress-strain hystereses with the microstructural changes, the complex interaction of the texture, the resulting anisotropy, and the tension-compression asymmetry under cyclic loading in the corrosive medium is to be characterized. The understanding of the process-microstructure-property relationships allows the development of a new group of high-performance extruded Mg alloys and the knowledge transfer to the fatigue and corrosion behavior of Mg sheet alloys in general, which forms a basis for sheet alloy development through cast rolling. Although the topic has a high scientific and economic potential, it has not been investigated yet, nor have the present damage mechanisms been researched regarding the texture influence on fatigue behavior and in particular the SCC.