A soil and magma mechanics approach to understanding defects in cast metals manufacturing

用于理解铸造金属制造中缺陷的土壤和岩浆力学方法

• 批准号: EP/K026763/1
• 负责人: Christopher Gourlay
• 金额: $ 47.94万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FK026763%2F1
• 关键词: soil; magma; mechanics; approach; understanding

We rely on metallic components every day, from cars and bridges to the solder joints in our electronics. In almost all cases, a step in the manufacture of these components is the solidification of liquid alloy, and it is during solidification that most defects arise. We are all familiar with ice expanding as it solidifies, making ice float on lakes and causing water-filled crevices in rocks and roads to crack open. Most metals do not expand on solidification, but shrink. If this shrinkage is not fed by liquid from elsewhere, a variety of defects can form: the outer surface of the casting can be deformed inwards, pores can grow in the liquid, or cracks can propagate along liquid films between grains, pulling the metal apart. In order to produce metals with fewer defects at a competitive cost, predictive models of defect formation in casting are required. To develop accurate models, we first need a better understanding of the fundamentals of deformation in semi-solid alloys.It has recently been found that solidifying metals share striking similarities to the soils that support our buildings and the partially-molten rock in the earth. In their semi-solid state, metals are made up of numerous crystals (solid particles) surrounded by liquid. Just as is the case of sand grains, these particles have been shown to move around each other when the material as a whole deforms, and the particles rotate and transmit forces between each other. An exciting aspect of this discovery is that the answers to solving metal-casting defects may not lie in the metallurgy section of the library but in the Civil Engineering and Earth Sciences sections. Indeed, models already exist for the deformation of soils and are widely used in Civil Engineering. However, the analogy between metals and soils has only been proven in small-scale experiments carried out to observe the individual particles in semi-solid metals. In the proposed research, we seek to conduct experiments inspired by soil and rock mechanics that will produce results suitable for testing whether the framework at the heart of soil mechanics theory can describe the deformation of semi-solid alloys.We aim to fit semi-solid alloy deformation into an over-arching framework for soils, magmas and metals. We will test scientifically whether semi-solid metals meet rules for behaviour specified within Critical State Soil Mechanics theory, developed in the UK in the 1960s. Three main hypotheses must be demonstrated:1. That the mechanical behaviour depends on the initial packing-density of the crystals: a densely packed material should experience a reduction in packing-density (dilation) when a shearing deformation is applied. The opposite effect (contraction) should be experienced in a loosely packed material.2. That the peak shear-stress that the material can resist depends on the overall-pressure acting on it.3. That there is some combination of crystal shape, packing-density and confining pressure where the material can deform without any overall change in packing-density.To achieve this goal, we will combine experimental approaches from soil, magma and metals research. We will use apparatus developed to study partially-liquid rock (magma) to obtain data on deforming semi-solid aluminium alloys at more than 500C. Next, to ensure the correct microscopic interpretation of the measurements, we will directly observe crystals within a semi-solid alloy as it is being deformed in a small-scale two-dimensional experiment using X-ray imaging in Japan. We will then develop an equivalent particle-scale computer model, based on soil mechanics, of the X-ray experiments to explore the forces acting at crystal-crystal contacts. When combined, the results from the experiments and modelling should enable us to put forward a new idea for the modelling of semi-solid metals.

从汽车和桥梁到电子产品中的焊接点，我们每天都依赖于金属部件。几乎在所有情况下，制造这些部件的一个步骤是液态合金的凝固，并且正是在凝固过程中出现了大多数缺陷。我们都熟悉冰在凝固时会膨胀，使冰漂浮在湖面上，并导致岩石和道路中充满水的裂缝裂开。大多数金属在凝固时不会膨胀，而是收缩。如果这种收缩没有来自其他地方的液体供给，就会形成各种各样的缺陷：铸件的外表面会向内变形，气孔会在液体中生长，或者裂纹会沿着晶粒之间的液膜传播，从而将金属拉开。为了以具有竞争力的成本生产具有较少缺陷的金属，需要铸造中缺陷形成的预测模型。为了建立精确的模型，我们首先需要更好地理解半固态合金变形的基本原理。最近发现，凝固的金属与支撑我们建筑物的土壤和地球上部分熔融的岩石有着惊人的相似之处。在半固体状态下，金属由许多被液体包围的晶体（固体颗粒）组成。正如沙粒的情况一样，当材料作为一个整体变形时，这些颗粒会相互移动，颗粒会旋转并相互传递力。这一发现的一个令人兴奋的方面是，解决金属铸造缺陷的答案可能不在于图书馆的冶金部分，而是在土木工程和地球科学部分。实际上，土壤变形的模型已经存在，并广泛用于土木工程。然而，金属和土壤之间的相似性仅在观察半固态金属中单个颗粒的小规模实验中得到证实。在这项研究中，我们试图进行受土壤和岩石力学启发的实验，这些实验将产生适合于测试土壤力学理论核心框架是否可以描述半固态合金变形的结果。我们的目标是将半固态合金变形拟合到土壤，岩浆和金属的过度膨胀框架中。我们将科学地测试半固态金属是否符合20世纪60年代在英国开发的临界状态土壤力学理论中规定的行为规则。必须证明三个主要假设：1。机械行为取决于晶体的初始堆积密度：当施加剪切变形时，密集堆积的材料应该经历堆积密度（膨胀）的降低。相反的效果（收缩）应该经历在一个松散的包装材料。2.材料所能承受的峰值剪应力取决于作用在其上的总压力.晶体形状、堆积密度和围压之间存在某种组合，在这种组合下，材料可以在不改变堆积密度的情况下变形。为了实现这一目标，我们将结合土壤、岩浆和金属研究的联合收割机实验方法。我们将使用为研究部分液态岩石（岩浆）而开发的仪器，以获得在500 ℃以上变形半固态铝合金的数据。接下来，为了确保测量结果的正确微观解释，我们将在日本使用X射线成像在小规模二维实验中直接观察半固态合金中的晶体。然后，我们将开发一个等效的粒子尺度的计算机模型，土壤力学的基础上，X射线实验，探索在晶体晶体接触的力量。当结合起来，从实验和模拟的结果应该使我们能够提出一个新的想法，半固态金属的模拟。

项目成果

In situ study of granular micromechanics in semi-solid carbon steels

• DOI: 10.1016/j.actamat.2013.03.043
• 发表时间: 2013-06-01
• 期刊: ACTA MATERIALIA
• 影响因子: 9.4
• 作者: Fonseca, J.;O'Sullivan, C.;Gourlay, C. M.
• 通讯作者: Gourlay, C. M.

Using DEM to assess the influence of stress and fabric inhomogeneity on susceptibility to suffusion

使用 DEM 评估应力和织物不均匀性对扩散敏感性的影响

• 发表时间: 2013
• 作者: Kawano,K

Synchrotron Radiography Studies of Shear-Induced Dilation in Semisolid Al Alloys and Steels

半固态铝合金和钢剪切诱发膨胀的同步辐射照相研究

• DOI: 10.1007/s11837-014-1029-5
• 发表时间: 2014
• 期刊: JOM
• 影响因子: 2.6
• 作者: Gourlay C

Dilatancy in semi-solid steels at high solid fraction

• DOI: 10.1016/j.actamat.2016.11.066
• 发表时间: 2017-02
• 期刊: Acta Materialia
• 影响因子: 9.4
• 作者: K. Kareh;C. O’Sullivan;T. Nagira;H. Yasuda;C. Gourlay

Revealing the micromechanisms behind semi-solid metal deformation with time-resolved X-ray tomography.

通过时间分辨 X 射线断层扫描揭示半固态金属变形背后的微观机制。

• DOI: 10.1038/ncomms5464
• 发表时间: 2014-07-18
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Kareh, K. M.;Lee, P. D.;Atwood, R. C.;Connolley, T.;Gourlay, C. M.
• 通讯作者: Gourlay, C. M.