Mechanical processing, compaction, and thermal processing of α-Fe powder

Abstract

High-energy ball milling is a proven technique for both mechanical alloying and for the production of nanocrystalline powders. In this U.S. Bureau of Mines study, it is found that mechanical processing pure α-Fe powders in a nitrogen environment results in nanocrystalline powders with nitrogen concentrations that increase linearly with time. In addition, processing in nitrogen results in a much smaller ultimate crystallite size than obtained in identical powders processed in argon. Consolidation of these powders by explosive compaction results in dense bodies that retain both their nanostructure and nitrogen content, whereas consolidation by HIPing results in retained nitrogen levels but a loss of nanostructure. Both the nanostructure and the high nitrogen levels of the explosively compacted materials are retained up to 863K.