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Thermodynamic Grain Size Stabilization Models: An Overview, Mostafa Saber, Carl C. Koch, Ronald O. Scattergood
Thermodynamic Grain Size Stabilization Models: An Overview, Mostafa Saber, Carl C. Koch, Ronald O. Scattergood
Mechanical and Materials Engineering Faculty Publications and Presentations
Grain boundaries in a nanocrystalline microstructure produce an increase in the excess free energy of the system. Grain growth is a consequence of the thermodynamic driving force reducing this excess. Thermodynamic stabilization is an approach based on eliminating the driving force by suitable alloy additions that can produce a metastable equilibrium state at the nanoscale grain size, as opposed to kinetic stabilization where the grain growth mobility is restricted by pinning and/or drag mechanisms. The present paper reviews and compares various models proposed for thermodynamic stabilization.
An In Situ Experimental Study Of Grain Growth In A Nanocrystalline Fe91ni8zr1 Alloy, Hasan Kotan, Kris A. Darling, Mostafa Saber, Ronald O. Scattergood, Carl C. Koch
An In Situ Experimental Study Of Grain Growth In A Nanocrystalline Fe91ni8zr1 Alloy, Hasan Kotan, Kris A. Darling, Mostafa Saber, Ronald O. Scattergood, Carl C. Koch
Mechanical and Materials Engineering Faculty Publications and Presentations
Grain growth and microstructural evolution of thermally stabilized Fe91Ni8Zr1 were investigated by in situ and ex situ studies. Our investigations suggest that the microstructural evolution is fairly slow and the microstructure shows stabilization up to about 700 °C. Above this temperature, a certain fraction of grains grow abnormally into the nanocrystalline matrix, resulting in a bimodal microstructure and causing the complete loss of thermal stability. The reason for abnormal grain growth and the loss of thermal stability is identified as the appearance of the fcc γ-phase and consequent reduction in the total area of grain boundaries and the overall stored …