Materials Processing Fundamentals: Molten Metal Processing
Sponsored by: TMS Extraction and Processing Division, TMS: Process Technology and Modeling Committee
Program Organizers: Jonghyun Lee, Iowa State University; Guillaume Lambotte, Boston Metal; Samuel Wagstaff, Oculatus Consulting; Antoine Allanore, Massachusetts Institute of Technology; Fiseha Tesfaye, Metso Metals Oy, Åbo Akademi University
Thursday 2:00 PM
February 27, 2020
Room: 13
Location: San Diego Convention Ctr
Session Chair: Samuel Wagstaff, Novelis Inc.; Allie Anderson, Gopher Resource
2:00 PM
Numerical Modelling of Additive Manufactured Ti-Al-Si-Cu/Ti-6Al-4V Composite by Direct Laser Metal Deposition (DLMD) Technique: Olawale Fatoba1; Stephen Akinlabi2; Esther Akinlabi2; Lester Naidoo2; 1Kent State University; 2University of Johannesburg
This research developed a numerical model based on the transport phenomena that takes place during the process of fabricating Ti-Al-Cu-Si/Ti-6Al-4V composite by Direct Laser Metal Deposition (DLMD) Technique. The process was simulated using a volumetric source of heat and the investigation focused upon studying how the Ti-Al-Cu-Si/Ti-6Al-4V reinforcement layer was influenced by the absorbed volumetric energy. Processing parameters such as laser intensity and the scanning speed were varied and employed to numerically design the DLMD single and multi-tracks. The influence of the processing parameters on the characteristics of the molten pool was examined. The dimensions of the molten pool varied in accordance to an invariant energy density. Although a combination of processing parameters might have resulted at the same energy density value. The utilization of independent processing parameters produced characteristics specific to the molten pool, but energy densities are in general proportional to the resulting characteristics of the molten pool.
2:20 PM
Influence of Laser Intensity and Speed of Scanning on the Ultimate Tensile Strength and Metallurgical Properties of Laser Cladded Ti-6Al-4V+Ni/Ti-6Al-4V Composite Coating: Olawale Fatoba1; Esther Akinlabi2; Stephen Akinlabi2; 1Kent State University; 2University of Johannesburg
The effects laser intensity and speed of laser scanning of Direct Laser Metal Deposition (DLMD) process had on the ultimate tensile strength, porosity generated, the hardness and the sizes of the grains in the Ti-6Al-4V alloy substrate cladded with reinforced Ti-6Al-4V/Ni coating were investigated. The temperature gradient and the rate of solidification of reinforcing the Ti-6Al-4V substrate with the Ti-6Al-4V/Ni power were also focused on in terms of how they were influenced by the laser intensity and the scanning speed used in the building process. An empirical design based on statistical analysis was employed which incorporated the Grey Relational Analysis (GRA) approach devised by Taguchi. The experiments produced results which revealed that the hardness of the clad was dependant highly on the laser scanning speed. Microstructural analysis on the substrate showed that the grain sizes were dominated by the laser processing intensity.
2:40 PM
A Quantitative Study of Microsegregation Mechanisms in Aluminum Binary Alloys: Zhenjie Yao1; Yang Huo2; Mei Li2; John Allison1; 1University of Michigan; 2Ford Motor Company
Understanding the microsegregation that occurs during typical solidification processes is important. The alloy partition coefficient describes the microsegregation behavior and can be directly used to calculate microstructural quantities. Previous research has shown that the alloy partition coefficient deviates from equilibrium in most solidification processes, however, no systematic method is available to predict this value over a range of solidification rates. Furthermore, very limited data can be found to verify existing models. In this presentation, several mechanisms that occur at different solidification rates will be quantitatively studied. The rate-dependent partition coefficient is inferred from a statistically meaningful EPMA measurement. In addition, a physics-based analytical method, verified by the experimental data, is employed to predict the microsegregation behaviors over a large range of solidification rates. This study will provide a quantitative prediction of microsegregation for different casting techniques for a number of important Al binary alloys.
3:00 PM
Contactless Ultrasound in Copper and Nickel Melts: Catherine Tonry1; Christopher Beckwith1; Valdis Bojarevics1; Georgi Djambazov1; Koulis Pericleous1; 1University of Greenwich
Contactless Ultrasound is a novel technique that uses a kilohertz frequency electromagnetic coil, known as “top-coil” to induce rapidly changing Lorentz forces in molten metals. At resonant frequencies these forces are sufficient to induce cavitation within the melt and it has been used to great effect in aluminium melts for grain refinement and degassing. Given the importance of resonance, a three dimensional acoustic/magnetic model of the melt and surrounding crucible has been developed and validated against experiments to predict the optimal conditions for cavitation. In contrast to traditional immersed sonotrode based methods, this contactless ultrasound method has the potential to work with higher temperature or reactive metals. The computational model has been extended to account for copper and nickel melts. Ahead of experiments, the results indicate that resonance, hence cavitation, is achievable in both of these cases using a set up similar to that for aluminium.
3:20 PM Break
3:40 PM
The Effect of Side Arcs on Current Distributions in Submerged Arc Furnaces for Silicon Production: Yonatan Tesfahunegn1; Thordur Magnusson2; Merete Tangstad3; Gudrun Saevarsdottir1; 1Reykjavik University; 2Stakksberg; 3Norwegian University of Science and Technology
Recent electromagnetic modeling efforts for submerged arc furnace allow improving understanding of the current distribution, which is critical for proper operation of furnaces for silicon production. This paper presents calculations of electric current distributions inside an industrial smelter. A 3D model has been developed in ANSYS Maxwell using the AC, eddy current solver. The modeled furnace operates with three-phase AC. In each phase, electrode, main arc, crater, crater wall, and side arcs that connect electrode and crater wall are taken into account. In this work, the number of side arcs is varied to study the effect on current distributions in different parts of the furnace, as well as skin and proximity effects in the electrodes. Also, the system resistance, active and reactive power distributions are investigated.
4:00 PM
Empirical Study of Laser Cleaning of Rust, Paint and Mill Scale from Steel Surface: Jean-Michaël Deschênes1; Alex Fraser1; 1Laserax Inc
In the last few years, demand for laser cleaning technology has significantly increased. Laser cleaning is the process by which contaminant are removed from a material surface by using a highly energetic focalised laser beam. Typical application of laser cleaning are paint and coating stripping, mold cleaning and rust removal. As many industrial applications required a short processing time, it is therefore a necessity to make laser cleaning process as efficient as possible. In this paper, we compared the performance of two types of fiber laser source for laser cleaning: single-mode and multi-mode. As these two types of lasers offers specific characteristics, we performed an empirical study to compare their performances in terms of cleaning speed for rust, paint and mill scale. Emphasis is put into the optimization of the optical parameters that maximize the cleaning speed with minimal substrate damage. Advantages and limitations of each system are also discussed.
4:20 PM
Heterogeneous Microstructure Induced Mechanical Responses in the Welded Joint of EH420 Shipbuilding Steel under High Heat Input Electro-gas Welding: Xie Xu1; Wang Cong1; 1Northeastern University
In order to improve shipbuilding efficiency, high heat input welding technology is widely used. However, welded joints under high heat input usually are subjected to unexpected microstructure deterioration, leading to inferior mechanical responses. In the present work, microstructural variation and mechanical properties of EH420 shipbuilding steel welded joint processed by 145 kJ/cm electro-gas welding were systematically studied. The results show that the weld metal structure is dominated by acicular ferrites, which can provide excellent toughness. The coarse grained heat-affected zone is mainly composed of lath bainites, granular bainites and martensite-austenite (M-A) constituents. Compared with CGHAZ, WM has higher toughness (129.3J vs. 37.3J) as it contains a large number of high-angle grain boundaries (frequency 79.2). It is found that effective Ti-Al-Mg-Mn-O complex inclusions promote the formation of acicular ferrites, which, in turn, obstruct the propagation of microcracks. Moreover, coarse austenite grains in CGHAZ and the presence of significant M-A constituents (average width 1.1μm) between bainite laths may likely contribute to toughness.