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NOVEL PROCESSING TECHNIQUES AND ALLOY ENGINEERING APPLIED TO ADVANCED RARE EARTH-IRON BASED PERMANENT MAGNET SYSTEMS

Objective

The development of techno-economically viable ma gnets based on NdFeB or other Rare Earth - Transition Metal - Metalloid systems. To be achieved through collaboration on alloy engineering, process innovation and development (including new techniques and surface effects such as corrosion studies). Specific objectives are improved thermal stability, better corrosion/oxidation resistance and minimal cost of finished magnets (cost/unit) performance. Investigations will focus on modification or replacement of the rare-earth rich phase, the possibilities for precipitation hardening systems and the feasibility of producing anisotropic material directly from rapid solidification processes (ST). Processes studied will include novel raw material casting techniques, hydrogen decrepitation, hot pressing, RST, resistance sintering, and any other novel routes appropriate to the overall aims. Target application areas are aerospace and automotive actuation, power generation industrial drives and domestic appliances.
Overall objectives of the project are to develop technoeconomically viable magnets based on neodymium iron boride or other rare earth transition metal-metalloid systems, through alloy engineering and process innovation. Aims are improved thermal stability, better corrosion/oxidation resistance and cost effectiveness. Main tasks are the modification or replacement of the rare earth rich phase, investigate the possibilities for precipitation hardening systems, feasibility of producing anisotropic material directly from rapid solification processes, process studies of novel raw material casting techniques, hydrogen decrepitation, hot pressing, RST and resistance sintering, thorough magnetic and microstructural characterisation of commercial and experimental materials, consideration of fitness forpurpose.
Results obtained include the development and understanding of the hydrogen disproportionation desorption recombination process (HDDR), an investigation of the link between microstructure, chemistry and magnetic behaviour of commercial sintered neodymium iron boride (incremental recoil permeability technique developed to study demagnetisation behaviour), the development of hot pressing techniques and brief study of resistance sintering, the development of disc casting process for control of ingot microstructure, the quantification of the recrystallisation process in prior amorphous melt spun alloys, the confirmation that anisotropic as cast melt spun alloys are unlikely to be feasible and precipitation hardening system discovered.

The overall objective has been develop technically and economically viable magnets based on neodymium iron boride or similar alloy systems through alloy engineering and process innovation. The reason was the need for improved thermal and environmental stability and cost effectiveness in appropriate applications.
The project has studied aspects of ingot/precursor material processing, powder production and magnet fabrication, including improvements and novel processes based on hydrogen decrepitation, flake/disc casting, melt spinning, resistance sintering and hot pressing.
Progress has been made in all areas, in particular control of precursor material through disc/flake cast processing, the potential of processes developed out of hydrogen decrepitation for providing stable powder of carefully controlled grain size, understanding recrystallization kinetics and behaviour of melt spun alloys, control of hot pressing, and the general relationship between microstructure, chemistry and magnetic properties in neodymium iron boride alloys. Results have indicated that the achievement of anisotropic ribbon directly from melt spinning and the development of precipitation hardening systems in such alloys are both extremely difficult.
ALLOY ENGINEERING WILL INCLUDE A SYSTEMATIC STUDY OF ALLOY CHEMISTRY, PHYSICS, CRYSTAL CHEMISTRY AND CONSTITUTIONAL STUDIES. DEVELOPMENT OF NOVEL TECHNIQUES SUCH AS PHASE ANALYSIS BY HYDROGENATION BEHAVIOUR. BASIC ALLOY CHEMISTRY INFORMATION WILL BE USED TO IDENTIFY NEW ALLOYS.

INITIAL INVESTIGATIONS WILL CONCENTRATE ON THE DEVELOPMENT OF PRECIPITATION HARDENING MATERIALS WITH IMPOSED THERMAL STABILITY. MODIFICATION OR SUBSTITUTION OF THE RE RICH PHASE WILL BE SOUGHT BY CONVENTIONAL OR MECHANICAL ALLOYING. RAPID SOLIDIFICATION (RST) AND HYDROGEN DECREPITATION (H-D), AS A MEANS OF MAGNET PROCESSING, WILL BE THE SUBJECT OF EXTENSIVE INVESTIGATIONS.

THE FEASIBILITY OF ALTERNATIVE BONDING AND CONSOLIDATION TECHNIQUES, INCLUDING NOVEL PROCESSES, WILL BE INVESTIGATED WITH PARTICULAR REFERENCE TO ANISOTROPY, DENSITY AND THERMAL/ENVIRONMENTAL STABILITY. IMPROVED MACHINEABILITY OF HOT-PRESSED MATERIAL THROUGH INCORPORATION OF A MECHANICALLY SOFT PHASE WILL ALSO BE ASSESSED.

EVALUATION WILL INCLUDE MEASUREMENT OF MAGNETIC PROPERTIES AT AMBIENT AND ELEVATED TEMPERATURES, AGEING EFFECTS AND LOSSES, AND PHYSICAL AND MECHANICAL PROPERTIES (E.G. THERMAL CONDUCTIVITY, SPECIFIC HEAT, STRENGHT).

SURFACE EFFECTS WILL BE STUDIED IN DETAIL, INCLUDING CORROSION STUDIES AND THE EFFECT OF DAMAGE DUE TO MACHINING OPERATIONS. CORROSION STUDIES WILL INVOLVE THE DEVELOPMENT OF A BASIC UNDERSTANDING FROM ELECTROCHEMISTRY AND ENVIRONMENTAL TESTING, AND THE ESTABLISHMENT OF CORROSION/OXIDATION CONTROL THROUGH INTRINSIC COMPOSITION OR PROTECTIVE COATINGS. THE USE OF PERMANENT MAGNET DEVICES IS INCREASING IN AREAS SUCH AS AEROSPACE AND AUTOMOTIVE ACTUATION AND POWER GENERATION, AND IN INDUSTRIAL AND DOMESTIC APPLICATIONS. EXPANSION OF THIS MARKET IS PARTLY DEPENDENT ON DEVELOPMENT OF HIGH PERFORMANCE AND COST EFFECTIVE PERMANENT MAGNETS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Lucas Automotive Ltd
Address
Dog Kennel Lane Shirley
B90 4JJ Solihull
United Kingdom

Participants (5)

GESELLSCHAFT FUER ELEKTROMETALLURGIE
Germany
General Electric Company plc
United Kingdom
Address
Hirst Research Centre
Micanite and Insulators Ltd
United Kingdom
UNIVERSIDAD DE PORTO
Portugal
Address

Porto
Universidad Autonoma de Barcelona
Spain
Address

8193 Barcelona