Structure Refinement Upon Ultrasonic Melt Treatment in a DC Casting Launder
- PDF / 7,071,693 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 39 Downloads / 162 Views
https://doi.org/10.1007/s11837-020-04269-3 2020 The Author(s)
SOLIDIFICATION BEHAVIOR IN THE PRESENCE OF EXTERNAL FIELDS
Structure Refinement Upon Ultrasonic Melt Treatment in a DC Casting Launder TUNGKY SUBROTO ,1,7,8 DMITRY G. ESKIN,1,2 CHRISTOPHER BECKWITH,3 IVAN SKALICKY,4 DAN ROBERTS,4 IAKOVOS TZANAKIS,5,6 and KOULIS PERICLEOUS3 1.—Brunel Centre for Advanced Solidification Technology (BCAST), Brunel University London, Uxbridge UB8 3PH, UK. 2.—Tomsk State University, Tomsk, Russia 634050. 3.—Computational Science and Engineering Group, University of Greenwich, 30 Park Row, London SE10 9LS, UK. 4.—Constellium UTC, Brunel University London, Uxbridge UB8 3PH, UK. 5.—Faculty of Technology, Design and Environment, Oxford Brookes University, Oxford OX33 1HX, UK. 6.—Department of Materials, University of Oxford, Oxford OX1 3PH, UK. 7.—e-mail: [email protected]. 8.—e-mail: [email protected]
This work focuses on ultrasonic melt treatment (UST) in a launder upon pilotscale direct chill (DC) casting of 152-mm-diameter billets from an AA6XXX alloy with Zr addition. Two casting temperatures (650C and 665C) were used to assess their effect on the resulting microstructure (grain size, particle size, and number density). Structure refinement results show the feasibility of UST in the DC casting launder. This is quantified through the corresponding reduction of grain size by around 50% in the billet center, or more towards the billet surface, reduction of the average Al3Zr particle size, and increase in the particle number density. A higher Al3Zr particle density was obtained when the alloy was cast at 665C. Numerical simulation results and suggestions on how to improve the treatment quality of UST in DC casting launder are also provided.
INTRODUCTION Direct-chill (DC) casting is a typical means of producing aluminum alloy billets suitable for further downstream processing.1 The quality and properties of the as-cast product are directly linked to its microstructure; finer structure commonly leads to superior mechanical properties,2 and better castability3,4 and formability for subsequent processing,5,6 and decreases the severity of casting defects.2 To refine the structure of aluminum alloys, typically TiB2 or TiC additions are used,2 but also individual elements such as Ti7 and Zr8,9 can produce grain refinement. Ultrasonic melt treatment (UST) is an attractive melt treatment technology because it enables a similar or even more significant structure refinement than that achievable with common grain refining practice, but with lesser amount of additions.10 This makes UST not only economically (Received April 23, 2020; accepted June 30, 2020)
appealing but also environmentally friendly. The structure refinement mechanism by UST has been comprehensively reviewed by Eskin and Eskin10 and the mechanisms can be summarized as enhanced heterogeneous nucleation through activation of latent nonmetallic inclusions (i.e., oxides) and fragmentation of primary intermetallics.9,10 These mechanisms are profoundly de
Data Loading...
