Development of a high-throughput magnetic characterization technique and its application to process parameter development for electron beam powder bed fusion of permalloy
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Colton, Stefan Luka
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Abstract
The autonomous experimentation paradigm has the potential to rapidly accelerate the development of materials and processes. It requires new characterization techniques with sufficient throughput to screen large numbers of samples. In this work, a methodology for measuring the magnetic properties of ferromagnetic samples is developed. The proposed methodology utilizes a simple, inexpensive desktop instrument designed to be amenable to automation. The use of the hardware and requisite data analysis methodology is validated and shown to have acceptable accuracy and repeatability for screening purposes; saturation magnetization is typically accurate to 1% and repeatable to 0.2%, while coercivity is repeatable to 20-30 A/m. The measurement time per specimen is under 20 seconds, with an architecture that allows significant further improvement. The cost of hardware is on the order of $1000 US, and there are minimal constraints on the acceptable geometry of samples. These characteristics are compared to existing techniques and shown to represent a favorable tradeoff for many screening applications.
This magnetic characterization technique is then demonstrated by accelerating the development of the Electron Beam Powder Bed Fusion (PBF-EB) additive manufacturing of Permalloy, a high-performance magnetic alloy used widely in electrical machinery. Over four hundred specimens were printed and characterized, utilizing the developed technique as well as other high-throughput measurements. Additionally, Active Learning was employed, allowing many experiments to be designed efficiently and autonomously. The use of high-throughput characterization and Active Learning enabled the effects of 6 factors to be explored simultaneously, including advanced scanning strategies of the electron beam. The effect of these factors on magnetic properties is analyzed; greater energy density and advanced scan strategies are found to result in a statistically significant increase in magnetization by approximately 1%. Four of the factors are also shown to have coupled effects on surface roughness. It is found that advanced scanning strategies can result in approximately a four-fold increase in the beam speed threshold for the onset of Plateau-Rayleigh instabilities affecting surface roughness. These results show the potential of high-throughput screening experiments to explore high-dimensional relationships and demonstrate the practical application of the developed magnetic characterization technique.
Finally, a method for the high-throughput characterization of the Coefficient of Thermal Expansion (CTE) is designed and prototyped. Initial results demonstrate the potential of the concept, which utilizes highly repeatable length measurements to eliminate the need for multiple furnace cycles when batch testing specimens. The method is shown to be a promising direction for future research that can introduce CTE characterization into an autonomous experimentation framework.
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Date
2023-08-25
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