Coupling Plasticity to Phase Transformations in Metastable Structural Alloys

在结构部件的设计中，设计师理想地寻找具有最大强度和可变形性（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，这两种特性是相互排斥的，即强度的增加通常会导致延展性的降低。虽然这种妥协源于材料的基本原子特性，但人们越来越意识到材料设计可以绕过固有的强度-延性关系。本提案旨在关注在单调和循环加载条件下使用控制变形（应变）诱导相变来提高强度和延性。这种方法将在具有商业意义的合金（钢和镁合金）中进行研究，特别是选择允许材料在变形过程中从一种状态变化到另一种状态。将开发工具来预测强度，延性和相变引起的变化之间的耦合。例如，原子尺度的模拟将用于系统地研究触发从一种状态到另一种状态变化的事件。先进的表征工具将用于同时评估力学行为和相变。结果将有助于我们对强度和延性之间内在关系的极限的基本理解，但也将为加拿大制造业的材料设计提供实用工具。

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.