microstructures within the material, and the possibility for enhancing material performance. This technique is a new synthesis-catalysis tool for overcoming reaction-activation barriers, and it has the potential to reduce processing energy and costs.
Dr. Ludtka then went on to describe numerous material properties that strong magnetic fields affect, including these:
• Phase stability;
• Diffusion barriers;
• Dislocation cores;
• Fault energies;
• Phonons and magnons;
• Kinetics, by raising temperatures and by affecting the critical stable nucleus for precipitate formation; and
Dr. Ludtka described a workshop conducted in 2005 by the National High Magnetic Field Laboratory to understand the needs of industry in X-ray and neutron effects. The workshop, Probing Matter at High Magnetic Fields with X-rays and Neutrons, resulted in a long list of material families and impact areas, including biological materials, synthesis of proteins, composite systems, and many, many others (Granroth et al., 2005). ORNL researchers are working to extend and realize some of these ideas.
Dr. Ludtka then very briefly described magnetic field processing at ORNL as a commercial-scale, synthesis-catalysis processing tool designed to impact phase equilibria and accelerate phase transformation kinetics. It is designed to simultaneously impact material properties such as strength, toughness, and phase equilibrium. The magnetic field processing facility at ORNL uses 9 T superconducting magnets with a vertical, 8 in. diameter bore.
Dr. Ludtka then explained why a high magnetic field shifts the phase boundaries of a material. There is a term in the free energy equation that is correlated with the external magnetic field (the integral expression in the equation below), although it is not traditionally considered to play a significant role:
∆G represents the change in free energy, α represents the ferrite fraction, and γ represents the austenite fraction in the Fe phase diagram, where a is the free energy for either ferrite or austenite. R is the gas constant and T is the temperature. In the integral H is the magnetic field and M the magnetization. Contrary to the assumption that the magnetic field term is unimportant, research at ORNL has shown that high-magnetic-field processing does have an impact on microstructure,