Papers by Keyword: Nanocrystallisation

Abstract: New opportunities for fabricating massive nanocrystalline materials in bulk quantities are required for facilitating the transition of nanocrystalline solids from laboratory samples to technologically relevant materials. Advanced options might be based on combining different nonequilibrium processing routes sequentially, such that an initially metastable state is continuously energized and successively driven farer away from thermodynamic equilibrium. The current paper presents recent results on the evolution of nanoscaled microstructures resulting from combinations of different plastic deformation treatments or of vitrification and severe plastic deformation.

Abstract: It has been well known that Hadfield steel behaviors excellent wear resistance under high impact energy. Up to now there exist many theories to explain the wear mechanism of Hadfield steel. In this research subsurface microstructure evolution process of Hadfield steel was investigated after high energy impact experiments. It was shown from high resolution electron microscope (HRTEM) examination of subsurface microstructure that nanocrystallized austenite grains have been formed in the procedure of the reaction and rearrangement of high density dislocations under the heavy plastic deformation, sub-grains as a transitional structure and, finally, the formation of nano austenite grains. On the other side, the interactions of twins and stack faults or dislocations and stack faults make austenite crystals transform to amorphous solid. With increasing impact cycles the sizes of nano-grains were decreased and the amorphous volumes were increased further. A large amount of nano-sized grains embedded in bulk amorphous matrix were fully developed, which will dominate the wear of the steel. In the subsurface no martensitic transformation was observed.

Abstract: Structure, magnetic and mechanical properties of the nanocrystalline composite material of the SILAME® type were tested. The composite material was obtained by solidification of the nanocrystalline powder obtained in the high energy grinding of the initially crystallized Co68Fe4Mo1Si13,5B13,5 amorphous strip with the silicon polymer. The metallic powder was mixed with the silicon polymer in a different weight ratio and next the effect of Co68Fe4Mo1Si13,5B13,5 powder weight ratio on the magnetic and physical properties of the composite was investigated.