Pioneered by Strange and Pim in the early twentieth century, melt spinning method has continually gained popularity as the best method for rapid solidification of certain types of alloys. Melt spinning is particularly used for fabricating metallic glasses as well as ribbons and foils that cannot be produced using conventional casting and rolling processes.
The original idea comprised of melting an alloy inside a cubicle, flushing out the melt through a nozzle right onto a rotating copper wheel, where the molten alloy solidifies rapidly. Recently, significant efforts have been made to enhance the efficiency in terms of quality, costs and productivity of melting spinning processes to fit the current market demands. Therefore, academic and industrial researchers have identified the critical parameters affecting the quality of melt-spun products, such as the melt temperature, ejection pressure, wheel speed and nozzle-wheel gap. However, despite the wide use of melt spinning processes for materials production in industries, fabrication of ribbons with high melting points has remained a challenge.
Current melt spinning operations involve manual release of the ejection gas by an experienced operator who carefully monitors the melt temperature and releases the ejection gas at the right moment. This process is susceptible to human errors thus resulting in the variations in the physical and chemical properties of the final products. A more challenging problem is associated with melt spinning of materials with high melting points, where transparent quartz tubes have to be replaced by the refractory opaque crucibles made of alumina or boron nitride. In such cases the operator would not be able to visually monitor the alloy condition and determine the correct ejection moment.
Recently, Dr. Amir A. Shirzadi from the Open University (UK) in collaboration with Dr. Tomasz Koziel, Dr. Grzegorz Cios and Dr. Piotr Bała from AGH University of Science and Technology (Krakow-Poland) developed an Auto Ejection Melt Spinning (AEMS) method and tested its feasibility in producing rapidly-solidified ribbons without the need of a skilled operator, i.e. effectively a hands-free process. The main aim was to minimize the uncertainties associated with manual temperature measurements and human errors. The research work has been published in Journal of Materials Processing Technology.
Using this new method, the uncertainties associated with the temperature measurements were substantially minimized due to the elimination of human and thermometry errors. Additionally, the effectiveness of this process was verified in fabrication of high strength ribbons with high melting points. The maximum tensile strength and ductility of the cobalt-based alloys were recorded as 138 MPa and 12.5% respectively.
In summary, the research team developed an automated melt spinning process for enhancing the performance and repeatability of the laboratory-based melt spinners equipped with gas ejection systems. The new process was successfully validated by an independent laboratory melt spinners manufacturer. Even though the study did not target replacing the automatic valves in large melt spinners, it will pave way for the advancement of these melt spinners by eliminating the need for skilled operators for manual monitoring of the process temperature.
A video clip which shows the ejection moment of a molten cobalt-based alloy during Auto Melt Spinning Process (AEMS).
Shirzadi, A., Kozieł, T., Cios, G., & Bała, P. (2019). Development of Auto Ejection Melt Spinning (AEMS) and its application in fabrication of cobalt-based ribbons. Journal of Materials Processing Technology, 264, 377-381.Go To Journal of Materials Processing Technology