Anomalous crystal growth in undercooled melts of Al-Ni and Cu-Zr alloy

Al-Ni 和 Cu-Zr 合金过冷熔体中的反常晶体生长

• 批准号: 179096895
• 负责人: Professor Dr. Markus Rettenmayr, since 12/2016 (†)
• 金额: --
• 依托单位: Institut für Experimentalphysik IV: Lehrstuhl für Festkörperphysik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/179096895?language=en
• 关键词: Anomalous; crystal; growth; undercooled; melts

Dendrite growth in undercooled melts of Al-Ni and Cu-Zr is anomalous in the sense that the growth velocity decreases with increasing undercooling. Such behaviour has not yet been observed in other metallic systems so far.Within the frame of the proposed project various parameters and processes will be investigated which can clarify such an anomalous growth characteristics. This is forced convection in the undercooled melts which can influence the heat and mass transport at the solid-liquid interface and the atomic impingement kinetics at the solidification front as well. All of these processes are essential for the control of the growth kinetics in undercooled melts. Furthermore, important parameters for modelling of growth kinetics will be determined by independent experiments and MD simulations. These are the temperature dependent diffusion coefficient and specific heat in the regime of the undercooled melt.In particular, the measurements of the specific heat are relevant to study inverse melting as the origin of the anomalous growth behaviour in Al-Ni melts. This process could explain the anomalous dendrite growth. Inverse melting is known for biophysical systems but in case of metallic system it is rather rarely investigated. There are some hints on inverse melting in specific metallic alloys like Cr-Ti.The growth of dendrites takes place both on a mesoscopic and a microscopic scale. Atomic diffusion and atomic attachment kinetics at the solid-liquid interface is controlled by the diffusion coefficient on a microscopic scale. Opposite to atomic diffusion the heat transport takes place on a mesoscopic scale since the thermal diffusivity is by about three orders larger than the atomic diffusion coefficient.Various experimental facilities are available to investigate the anomalous growth kinetics from various sides. Levitation (electromagnetic and electrostatic) allows for large undercoolings due to the complete avoidance of heterogeneous nucleation on container walls. By means of a high speed camera the advancement of the solidification front is measured with high precision. Comparative studies on Earth and in reduced gravity on the International Space Station will lead to an evaluation of the influences of convection on growth kinetics. The parameters needed for modelling of dendrite but also eutectic growth are independently determined in order to narrow the parameter space down. These versatile investigations should lead to an understanding of the anomalous growth kinetics in the alloys under investigations.

Al-Ni和Cu-Zr过冷熔体中枝晶生长是反常的，即生长速度随过冷度的增加而降低。这种行为还没有在其他金属系统中观察到迄今为止。在拟议的项目的框架内，各种参数和过程将进行调查，可以澄清这种异常的生长特性。这是强迫对流在过冷熔体中，可以影响在固液界面处的热量和质量的传输和原子碰撞动力学在凝固前沿以及。所有这些过程对于过冷熔体中生长动力学的控制是必不可少的。此外，生长动力学建模的重要参数将通过独立实验和MD模拟来确定。它们是过冷熔体中与温度有关的扩散系数和比热，特别是比热的测量对于研究Al-Ni熔体中反常生长行为的起源--逆熔化是相关的。这一过程可以解释枝晶的异常生长。逆熔化是已知的生物物理系统，但在金属系统的情况下，它是相当少的研究。在特定的金属合金如Cr-Ti中有一些关于反向熔化的暗示。枝晶的生长在介观和微观尺度上都发生。原子在固液界面的扩散和附着动力学在微观尺度上由扩散系数控制。与原子扩散相反，热输运发生在介观尺度上，因为热扩散系数比原子扩散系数大三个数量级。各种实验设备可用于从各个方面研究反常生长动力学。悬浮（电磁和静电）允许大的过冷，由于完全避免容器壁上的异质成核。通过高速照相机，以高精度测量凝固前沿的推进。通过在地球上和在国际空间站重力降低的情况下进行比较研究，将对对流对生长动力学的影响进行评价。枝晶和共晶生长建模所需的参数是独立确定的，以缩小参数空间。这些多功能的调查应导致下调查的合金中的异常生长动力学的理解。

项目成果

The effect of flow regime on surface oscillations during electromagnetic levitation experiments

• DOI: 10.32908/hthp.v49.817
• 发表时间: 2020-01-01
• 期刊: HIGH TEMPERATURES-HIGH PRESSURES
• 影响因子: 1.1
• 作者: Bracker, G. P.;Baker, E. B.;Hyers, R. W.
• 通讯作者: Hyers, R. W.

Dendrite growth in undercooled Al-rich Al-Ni melts measured on Earth and in Space

• DOI: 10.1103/physrevmaterials.3.073402
• 发表时间: 2019-07-16
• 期刊: PHYSICAL REVIEW MATERIALS
• 影响因子: 3.4
• 作者: Herlach, D. M.;Burggraf, S.;Valloton, J.
• 通讯作者: Valloton, J.

Modeling of Fluid Flow Effects on Experiments Using Electromagnetic Levitation in Reduced Gravity

流体流动对减重电磁悬浮实验影响的建模

• DOI: 10.1007/978-3-030-05728-2_16
• 发表时间: 2019
• 期刊: Materials Processing Fundamentals 2019
• 作者: G. Bracker;X. Xiao;J.H. Lee;M. Reinartz;S. Burggraf;D.M. Herlach;M. Rettenmayr;D. Matson;R.W. Hyers
• 通讯作者: R.W. Hyers