A Microstructural Approach Toward Synthesizing High Temperature Stable Nano-Crystaline Oxygen-Free Alloys
In this study, experimental results have been analyzed regarding the improving nano-grain size stability at elevated temperatures by the elimination of oxygen that may induce kinetic or/and thermodynamic stabilization. Low oxygen content powders of high purity elemental Fe and Cr were produced in a glove box by mechanically filing the solid materials. Fe-10Cr nanocrystalline alloy powders were processed using these elemental powders in conjunction with SPEX ball milling. The XRD, TEM and field emission SEM were employed to investigate the grain-size stability of the nanocrystalline alloy powders of Fe-10Cr up to isochronal temperature of 700. It has been showed that reducing the amount of oxygen can improve the grain size stability of Fe-10Cr via kinetic mechanism. Grain-size stabilization in Fe-10Cr alloy would be a result of solute drag by the Cr solutes at lower temperatures. The results from previous investigations on Fe-10Cr nanocrystalline alloys were (unknowingly at the time) influenced by the fact that the commercially available high purity elemental powders used for SPEX ball mill processing contained significant amounts of oxygen impurity. The results obtained in this investigation using identical processing methods with low oxygen content powders for synthesizing the alloys provide further insight into the stabilization mechanisms when compared to the previous results. Although this study suggests a new class of alloys with lower contamination, more investigation is necessary to determine the influence of oxygen elimination on mechanical properties of the alloy.