Materials Engineering of Soft Magnets for Power and Energy Applications: Advanced Silicon Steels and Soft Magnetic Alloys for Rotating Electrical Machinery
Sponsored by: TMS Functional Materials Division, TMS: Energy Conversion and Storage Committee, TMS: Magnetic Materials Committee
Program Organizers: Paul Ohodnicki, National Energy Technology Laboratory; Francis Johnson, GE Global Research; Alex Leary, Carnegie Mellon University; Tanjore Jayaraman, University of Michigan; Lajos Varga, Wigner Research Center for Physics

Thursday 2:00 PM
March 2, 2017
Room: 25B
Location: San Diego Convention Ctr

Session Chair: Alex Leary, Carnegie Mellon University

2:00 PM  Invited
Advanced Soft Magnetic Materials for Highly-efficient Electric Motors: Josefina Silveyra1; Satoru Simizu2; Michael McHenry2; 1INTECIN, Facultad de Ingenierķa, Universidad de Buenos Aires - CONICET; 2Carnegie Mellon University
    For the past decades amorphous and nanocomposite soft magnets have been a hot topic in the field of strategic materials based on their outstanding soft magnetic properties for a wide frequency-range. These materials successfully entered the market for low-frequency power transformers, high-frequency power electronics, magnetic shields, and sensor applications. Because electric motors account for nearly half of global electricity consumption, advanced soft magnets capable of operating with low losses at high speeds have the potential to greatly provide energy-savings. But the adoption of these unconventional materials for electric motors requires advances in suitable and cost-efficient manufacturing processes. In this work, we examine the role of soft magnetic materials in electric machines and discuss current materials’ limitations. We review recent efforts and technological achievements of emerging amorphous and nanocomposite soft magnets in the high-efficient electric motors field.

2:30 PM  Invited
Opportunities and Challenges in the Additive Manufacture of Soft Magnetic Silicon Steel Parts: Processing, Material Properties and Component Design: Michele Garibaldi1; Ian Ashcroft1; Richard Hague1; 1The University of Nottingham
    We show for the first time that Selective Laser Melting (SLM), a powder-based Additive Manufacturing technology, can offer an alternative route to produce functional silicon steel components for electromechanical applications. This is achieved thanks to the good soft magnetism of the processed parts (coercivity less than 20 A/m, maximum permeability of over 20000) and a Topology Optimization (TO)-based approach to component design. We propose an applicative example where the rotor core of an existing synchronous electrical machine has been redesigned by means of both TO and manufacturing considerations aimed at best exploiting the unparalleled design freedoms that the layer-wise nature of SLM makes possible. Results show that the combination of freeform design and good magnetic properties could potentially lead to the development of electrical machines characterised by improved torque density. This property could prove particularly attractive for applications where weight saving is important, i.e., in the automotive and aerospace sectors.

3:00 PM  Invited
Effect of Annealing Time on the Texture of a 2.8% Si Non-Oriented Electrical Steel after Inclined and Skew Rolling: Mehdi Mehdi1; Youaliang He2; Erik Hilinski3; Afsaneh Edrisy4; 1University of Windsor/Canmet Materials; 2Canmet Materials; 3Tempel Steel; 4University of Windsor
    Non-oriented electrical steels are widely used in electric motors and generators as core materials to amplify magnetic flux and thus enhancing the conversion of energy. The efficiency of the motors and generators is closely related to the magnetic properties of the lamination core. In order to produce the magnetically favourable <001>//ND texture (θ-fibre) and suppress the unfavourable <111>//ND (γ-fiber) components in non-oriented electrical steels, two unconventional cold rolling schemes (inclined and skew rolling) were employed to process the steel. These rolling schemes have shown great potential in altering the texture of non-oriented electrical steel, especially for the 60° (inclined rolling) and 22.5° (skew rolling) angles. In this paper the effect of annealing time on the texture evolution of a 2.8 wt% Si steel was investigated using EBSD techniques. It was found that, all the unconventional rolling schemes were able to produce a strong θ-fiber texture, but the annealing time to achieve this texture was different.

3:30 PM Break

3:45 PM  Invited
Effects of Cooling Rate on 6.5% Silicon Steel Ordering: Brandt Jensen1; Chad Macziewski1; Kevin Dennis1; Lin Zhou1; Wei Tang1; Olena Palasyuk1; Levitas Valery2; Matthew Kramer1; Jun Cui2; 1Ames Laboratory; 2Iowa State University
    Increasing Si content improves magnetic and electrical properties of electrical steel, with 6.5% Si as the optimum. Unfortunately, when Si content approaches 5.7%, the Fe-Si alloy becomes brittle. At 6.5%, the steel conventional cold rolling process is no longer applicable. The heterogeneous formation of B2 and D03 ordered phases is responsible for the embrittlement. The formation of these ordered phases can be impeded by rapid cooling. However, only the cooling rates of water and brine water were investigated. A comprehensive study of the effect of rapid cooling rate on the formation of the ordered phases was carried out by varying wheel speed and melt-injection rate. Thermal imaging employed to measure cooling rates while microstructures of the obtained ribbons are characterized using X-ray diffraction and TEM. The electrical, magnetic and mechanical properties are characterized using 4-pt probe, VSM, and macro-indentation methods. The relations between physical properties and ordered phases are established.

4:15 PM  
Novel Silicon Steel Nanocomposites via Severe Shear Deformation Approaches: Trevor Clark1; Hellen Jiang2; Nicole Overman2; Suveen Mathaudhu1; 1University of California, Riverside; 2Pacific Northwest National Laboratory
    There has been a push to develop a magnetic material with minimal core loss for use in electric motors to improve efficiency. Laminated silicon steel has been one of the primary materials of interest because of its high permeability and low conductivity which reduces hysteresis loss. These properties can be further enhanced by tuning the microstructure to increase grain boundary scattering and thus resistivity of the material to reduce the need for the non-magnetic laminates. This talk will compare the results of top-down and bottom-up approaches to producing nanograined bulk silicon steels. Samples processed by severe plastic deformation are compared to those processed by high-energy ball milling and sintering. Properties studied include the effect of grain size and grain boundary characteristics on resistivity and permeability. These findings will help to advance electric motor technology by improving efficiencies, and have widespread energy impacts.

4:35 PM  
Magnetic Properties of Shear-textured Fe-Si Sheet Produced by Simple Shear Deformation: Andrew Kustas1; Srinivasan Chandrasekar1; Kevin Trumble1; 1Purdue University
    Iron silicon (Fe-Si) alloy sheets possess favorable magnetic properties for use in electric motors and transformer cores. Commercial processing of these sheets involves multiple rounds of hot and cold rolling with intermediate annealing. Previously, a novel, single-step processing approach was used to produce continuous sheets from high silicon (>3wt%Si) Fe-Si alloys using a hybrid cutting extrusion process called large strain extrusion machining (LSEM). LSEM was shown to develop controlled simple shear textures in sheet with variable grain sizes from a range of Fe-Si compositions. In this study, preliminary magnetic properties of the shear-textured Fe-Si sheets are reported using a closed-loop permeameter. Measured properties include maximum relative permeability, coercivity, hysteresis loss, and saturation induction. These properties are evaluated as independent functions of sheet texture, grain size and composition. Implications for controlling the magnetic properties via LSEM are discussed and properties are compared with some expectations from a simple unit cell model.