Enhanced strength and ductility of wrought magnesium alloys through alloying with rare earth elements

当今先进世界的挑战迫使人们对交通运输中使用的镁等轻质合金的需求十分旺盛。尽管变形镁合金具有许多优异的性能，但由于低温成形性不足，变形镁合金的应用仍然受到限制，这直接归因于热机械加工过程中织构和组织发展不足。与典型的变形镁合金(如AZ31、ZK60)形成的强烈的机械各向异性相关的尖锐变形织构相比，含稀土的镁合金产生的织构更弱、更不常见，有助于提高环境成形性和降低力学各向异性。虽然稀土添加对织构随机化的影响已有报道，但观察到的织构改变的机理仍不是很清楚。本项目的目的是对镁稀土合金的变形和再结晶进行全面的研究，为优化强度和塑性的镁变形合金的设计策略提供新的思路。重点研究了单一稀土元素的添加及其对变形特征、再结晶机制和织构发展的影响。通过确定控制机制，我们应该能够推导出优化机械性能的微结构和织构工程的概念。

The challenges of today's advanced world are enforcing a strong demand for light alloys based for e.g. on magnesium to be used in transportation. Despite many attractive properties the applications of wrought magnesium alloys is still limited due to insufficient low temperature formability, which is directly attributed to an inadequate texture and microstructure development during thermomechanical processing. By contrast to typical wrought Mg alloys (e.g. AZ31, ZK60) which develop sharp deformation textures associated with strong mechanical anisotropy, rare earth (RE)-containing Mg alloys develop much weaker and less common textures that contribute to the enhancement of ambient formability and the reduction of the mechanical anisotropy. Although the effect of RE additions on randomizing the texture has been reported, the mechanisms of the observed texture modification are still not conclusively understood. The objective of this project is to conduct comprehensive investigations of deformation and recrystallization of Mg-RE alloys that will shed a new light on design strategies of Mg wrought alloys with optimized strength and ductility. The main focus is set on investigating single RE additions and exploiting their influence on the deformation characteristics, the recrystallization mechanisms, and the corresponding texture development. By identifying the controlling mechanisms, we should be able to derive a concept for microstructure and texture engineering for optimized mechanical properties.