Coupling Plasticity to Phase Transformations in Metastable Structural Alloys

在结构部件的设计中，设计者理想地寻求具有最大强度和变形性（延展性）的材料。前者允许使用较少的材料来承受给定的力，而后者赋予韧性（在失效之前吸收能量的能力）。不幸的是，在大多数材料中，这两种性质是相互排斥的，即增加强度通常会导致延展性降低。虽然这种妥协起源于材料的基本原子性质，但人们越来越意识到材料设计可以规避内在强度-延展性关系。该建议旨在集中于使用受控变形（应变）诱导相变，以实现在单调和循环加载条件下的强度和延性的改善。这种方法将在专门选择的具有商业意义的合金（钢和镁合金）中进行研究，以允许材料在变形过程中从一种状态变为另一种状态。将开发工具来预测强度，塑性和相变引起的变化之间的耦合。 例如，将使用原子尺度的模拟来系统地研究触发从一种状态到另一种状态的变化的事件。 先进的表征工具将用于评估机械性能和相变同时进行。结果将有助于我们的强度和韧性之间的内在关系的限制的基本理解，但也将提供实用的工具，材料设计的价值，加拿大制造业。

In the design of structural components the designer ideally seeks materials that have maximum strength and deformability (ductility). The former allows less material to be used to withstand a given force, while the latter confers toughness (the ability to absorb energy prior to failure). Unfortunately, in the majority of materials these two properties are mutually exclusive, i.e. increasing the strength generally leads to a reduction in ductility. While this compromise has its origins in the fundamental atomic properties of materials, there is an increasing awareness that material design can circumvent the intrinsic strength - ductility relationship. This proposal seeks to focus on the use of controlled deformation (strain) induced phase transformations to achieve improvements in both strength and ductility under monotonic and cyclic loading conditions. This approach will be investigated in alloys of commercial significance (steels and magnesium alloys) specifically selected to allow for the change of the material from one state to another during deformation. Tools will be developed to predict the coupling between strength, ductility and the changes induced by the phase transformation. Atomic scale simulations will be used, for example, to systematically investigate the events that trigger the change from one state to another. Advanced characterization tools will be used to assess the mechanical behaviour and phase transformation concurrently. The results will contribute to our fundamental understanding of the limits of the intrinsic relationship between strength and ductility but will also provide practical tools for materials design of value to the Canadian manufacturing industry.