Multi-length scale studies of early stage precipitation hardening phenomena in Al and Mg alloys

可热处理的AA 6xxx（即，Al-Mg-Si-（Cu）合金由于其所需性能的组合而属于最广泛使用的结构材料。这些合金用于几类豪华汽车或卡车的面板应用。然而，轻量化的紧迫性也使人们对它们在主流汽车中的使用产生了极大的兴趣。这些面板通常通过冷冲压制造，然后在烤漆循环（PBC）期间沉淀硬化。优化PBC的工业趋势是缩短加热时间和使用较低的温度。如果合金成分和/或加工历史没有适当地优化，这些工艺要求可以将沉淀限制在相对早期的阶段，并且不利地影响硬化。这种优化和设计更高强度的合金和成本有效的处理路线需要深刻理解的机制，支配溶质聚集和早期沉淀现象。申请人在该领域的最新工作突出了在Al合金的时效硬化期间发生的早期现象的知识的主要差距。特别是，需要一个全面的原子到宏观尺度的调查，以了解合金成分，变形和早期沉淀硬化的动力学之间的关系。

Heat treatable AA6xxx (i.e., Al-Mg-Si-(Cu)) alloys are among the most widely used structural materials owing to their combination of desirable properties. These alloys are used for panel applications in several classes of luxury automobiles or trucks. However, the urgency for lightweighting has created significant interest in their use in main stream automobiles, as well. These panels are commonly-fabricated by cold stamping and then precipitation hardened during paint bake cycling (PBC). The industrial trend in optimizing PBC is towards shortening heating times and using lower temperatures. These process requirements can limit precipitation to relatively early stages and adversely affect hardening, if alloy compositions, and/or processing histories are not properly optimized. Such optimizations and the design of higher strength alloys and cost effective processing routes requires a deep understanding of the mechanisms that govern solute clustering and early stage precipitation phenomena. The applicant’s most recent work in this area has highlighted the major gaps in knowledge of the early-stage phenomena that occur during age hardening of Al alloys. Particularly, a comprehensive atomic-to-macro length scale investigation is needed to understand the relationships between alloy compositions, deformation and the kinetics of early-stage precipitation hardening.