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In this study, Fe74Cr18Ni8 stainless steel was nanostructured by mechanical alloying from elemental powders with Y and nano-sized Y2O3 addition and subjected to annealing treatments at various temperatures up to 1100°C. X-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy were used to investigate the microstructural evolution as a function of annealing temperatures. The dependence of hardness on the microstructure was utilized to study the mechanical changes with annealing temperatures. It was found that the resulting microstructures were bcc solid solutions, the so-called - martensite structure due to the severe plastic deformation during mechanical alloying. Annealing induced reverse transformation from martensite to austenite and the ratio of which was found to be a function of annealing temperatures. As-milled nanocrystalline Fe74Cr18Ni8 steel yielded grain growth upon annealing reaching to micron sizes at high temperatures while addition of Y and Y2O3 stabilized the grain size and hardness around 150 nm and 6,5 GPa, respectively, after annealing at 1100°C. [ABSTRACT FROM AUTHOR]

In this study, Fe74Cr18Ni8 stainless steel was nanostructured by mechanical alloying from elemental powders with Y and nanosized Y2O3 addition and subjected to annealing treatments at various temperatures up to 1100 ºC. X-ray diffraction experiments, transmission electron microscopy and focused ion beam microscopy were used to investigate the microstructural evolution as a function of annealing temperatures. The dependence of hardness on the microstructure was utilized to study the mechanical changes with annealing temperatures. It was found that the resulting microstructures were bcc solid solutions, the so-called α'- martensite structure due to the severe plastic deformation during mechanical alloying. Annealing induced reverse transformation from martensite to austenite and the ratio of which was found to be a function of annealing temperatures. Asmilled nanocrystalline Fe74Cr18Ni8 steel yielded grain growth upon annealing reaching to micron sizes at high temperatures while addition of Y and Y2O3 stabilized the grain size and hardness around 150 nm and 6,5 GPa, respectively, after annealing at 1100 °C. [ABSTRACT FROM AUTHOR]

The key characteristic of ball-milled powders consolidation process is to achieve densification and particle bonding without degradation in mechanical properties. Recent demonstrations of novel processing methods involving temperature, high shear and high pressure have shown promise for bonding high strength particulate materials. In this study, we report the ability of multi-pass high temperature equal channel angular extrusion (ECAE) and hot pressing to produce fully dense and well-bonded bulk Ferritic alloys from nanocrystalline Fe- Ni-Zr powders. Subsequent microstructural characterizations indicate full consolidation via hot extrusion with grain growth to micron sizes. The consolidated alloys demonstrate an extremely high strength (4-6 GPa) at room temperature. [ABSTRACT FROM AUTHOR]