Reducing Emissions by Exploiting Field-Induced Martensitic Transformations

该研究金的目的是开发分析工具，以设计和使用利用应力和电磁场影响相变的材料。该领域从钢中的贝氏体和马氏体延伸到钛和锆合金中的β-> α转变期间的变体选择问题，从β-Ti合金GUM金属中的ω超弹性延伸到NiTi形状记忆合金（SMA）和铁磁SMA。在组件环境中，传统SMA依赖于温度变化来提供致动，这是被动地响应于环境或通过使用引气、电阻加热或加热丝加热/冷却来实现的。铁磁SMA使用电磁场，这允许更快的切换，例如在泵中或改善流量控制。虽然这些转换的晶体学是很好的理解，模型通常不适用于微观力学，可以纳入有限元（FE）的描述，设计师使用的组件的行为。此外，虽然这些系统显然易于处理原子方法，但原子建模仍然太不成熟，无法在没有实验支持的情况下可靠地设计新合金;然而，密度泛函理论（DFT）等方法可以使人们深入了解合金设计方法。一个次要目标是开始弥合与DFT界的差距。在常规合金中，问题通常由于转变的扩散成分而复杂化，或者成核可能是限制步骤。然而，我们最近已经清楚地表明，施加的应力可以偏向变体选择，导致在Ti-6246中产生单变体转化的β晶粒，从而对性能产生影响。在无扩散转变中（例如钢中的马氏体、Ti和Zr中的Ω以及（f）SMA中）对变体选择进行建模的能力将是对Ti-64和Ti-6246中更复杂问题进行建模的先决条件。在工业上，该奖学金的主要目标将是建立一个能力，以模拟这种转变，并设计合金利用它们用于航空航天，汽车和电力应用，与QinetiQ，劳斯莱斯，Timet，Corus和DSTL。

The aim of the the fellowship will be to develop the analysis tools to design and use materials that exploit stress- and electromagnetic field-affected phase transformations. This area extends from bainite and martensite in steels to the variant selection problem during the beta->alpha transformation in titanium and zirconium alloys, from omega superelasticity in the beta-Ti alloy GUM metal to NiTi shape memory alloys (SMAs) and ferromagnetic SMAs. In the component context, conventional SMAs rely on a temperature change to provide actuation, which is achieved either passively in response to the environment or by heating / cooling using bleed air, resistance heating or heating filaments. Ferromagnetic SMAs use an electromagnetic field, which allows much faster switching, for example in a pump or to improve flow control. While the crystallography of these transformations is well understood, models are not generally available for the micromechanics that can be incorporated into Finite Element (FE) descriptions of component behaviour used by designers. In addition, whilst these systems are clearly tractable to atomistic approaches, atomistic modeling is still too immature to reliably design new alloys without experimental support; however approaches such as density functional theory (DFT) can enable insight into alloy design approaches to be developed. A subsidiary aim will be to start to bridge the gap to the DFT community. In conventional alloys the problem is often complicated by a diffusional component to the transformation, or nucleation may be the limiting step. However, we have recently shown clearly that applied stress can bias variant selection, leading to the production of mono-variant transformed beta grains in Ti-6246, with consequent effects on properties. The ability to model variant selection in diffusionless transformations, such as in martensite in steels, omega in Ti and Zr, and in (f)SMAs will be a prerequisite to modeling the more complicated problem in Ti-64 and Ti-6246. Industrially, the major goal of the fellowship will be to build a capability to model such transformations and to design alloys exploiting them for use in aerospace, automotive and power applications, with QinetiQ, Rolls-Royce, Timet, Corus and DSTL.