Cast Shop Technology: Grain Refinement and Cast Structure
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee
Program Organizers: Johannes Morscheiser, Novelis Koblenz GmbH

Wednesday 2:00 PM
February 26, 2020
Room: 1B
Location: San Diego Convention Ctr

Session Chair: Philippe Jarry, Constellium

2:00 PM Introductory Comments

2:05 PM
Impact of TiB2 Particle Size Distribution on Grain Refining Effectiveness: Akihiro Minagawa¹; ¹UACJ Corporation /National Institute of Advanced Industrial Science and Technology(AIST)
    Al-Ti-B system grain refiner which includes TiB2 particles is added into molten Aluminum due to achieve the fine grains. The mechanism of grain refinement has been proposed that the TiB2 particles work as the heterogeneous nuclei. However the effect of grain refinement greatly fluctuates with grain refiner manufacturers and the lots despite the same composition. Furthermore, although a various features for the grain refiner exist, it is unclear which feature is the most effective for grain refining. In this study, the effect of grain refinement was investigated by using several grain refiners with different manufacturers and different compositions. TiB2 particle size distribution in grain refiner was measured by image analysis and applied to the grain size prediction model which is developed based on the free growth model. The experimental results and predicted values were compared and discussed.

2:30 PM
Effect of Nucleant Particle Size Distribution on the Grain Refining Efficiency of 7xxx Alloys: Georges Salloum-Abou-Jaoude¹; Philippe Jarry¹; Pierre Celle¹; Emmanuelle Sarrazin¹; ¹Constellium C-Tec
     To refine the as-cast grains of aluminium alloy products, the industry uses grain refiners of different nature, Al-Ti-B or Al-Ti-C. It is commonly known, that depending on their nature, grain refiners have different nucleant particle size distributions. In this work, we highlight the presence of significant differences in particle size distributions in grain refiners of the same nature depending on the producer, but also inconsistencies within production batches from the same manufacturer. We demonstrate the importance of the grain refiner nucleant size distribution on the grain refiner efficiency for aluminium alloys by means of SEM analysis and grain refiner casting tests. We discuss the phenomena linking nucleant particle size distribution to grain refiner efficiency by modelling and in situ X-ray radiography of solidification experiments.Using our experimental and modelling results, we emphasise the necessity of controlling the nucleant particle size distribution to assure grain refiner efficiency.

2:55 PM
Application Ultrasonic Technology Processing for Aluminum Treatment While Casting Slabs on Industrial Equipment of UC RUSAL: Igor Kostin¹; Aleksander Krokhin¹; Viktor Frolov¹; Aleksey Startsev¹; Sergei Bochvar²; Igor Bobkov¹; Nikita Lashchukhin¹; ¹UC RUSAL; ²IMET RAS
     The article considers the opportunities of using ultrasonic treatment to create conditions conducive to modify of the structure, as well as conditions that reduce the consumption of the supplied modifying rod for large-sized slabs of 5083 alloy manufactured by DC casting. Established the effective power range of ultrasonic waves for influencing the melt and the effective flow rate of the modifying rod supplied together with the use of ultrasound. The reduction in modifier consumption is due to the effect of advanced cavitation on TiB2 agglomerates, as well as “activation”, i.e., wetting of potential nucleating particles, thereby creating more crystallization centers.It is shown that the use of ultrasonic treatment promote to the removal of dissolved gases from the melt in industrial production. The removal of gases, similar to the modifying of the structure, is promoted by cavitation, forming microzones of different partial pressure, grabbing the gases dissolved in the melt.

3:20 PM
Influence of Liquid Jet Stirring and In-situ Homogenization on the Intermetallics Formation During DC Casting of a 6xxx Al Alloy Rolling Ingot: Kumar Sundaram¹; Jocie Cracroft¹; Robert Wagstaff¹; ¹Novelis
    Due to high cooling rate, the direct chill cast ingot solidifies under a non-equilibrium solidification condition that results in the formation of non-equilibrium intermetallics. Some of the solidified intermetallics are brittle, coarser and have a lower melting point, hence complicating the downstream thermomechanical processes and affecting the final sheet properties such as toughness and corrosion. Therefore it is essential to control the intermetallic formation during casting. In the current study, we show the influence of jet stirring and in-situ homogenization on the formation of intermetallics during DC casting of a 6xxx Al alloy rolling ingot. In particular, the intermetallic phase content through the ingot thickness has been characterized using various microscopes, a differential scanning colorimeter and X-ray diffractometer. Phenol intermetallic extraction has been used to facilitate the three dimensional chemistry and volume fraction of intermetallics, with changes rationalized in terms of the effect of jet stirring and in-situ homogenization pre-treatment.