Milling media and alloying effects on synthesis and characteristics of mechanically alloyed ODS heavy tungsten alloys

Oxide dispersion strengthened (ODS) tungsten heavy alloys produced by mechanical alloying exhibit high creep strength at elevated temperatures and good penetration performance. The effect of process parameters during mechanical alloying is important in determining material properties. In this study, we have examined different grinding media and have varied the composition of alloying elements to investigate their effect on grinding performance and microstructure evolution. The composition of the milled powders can be changed due to the wear of the grinding media and can form different phases, which results in a significant effect on microstructural development and material properties. Our results show that alloys milled by a stainless steel grinding media encourage the formation of iron-tungsten carbides and iron-tungsten intermediate phases, which deteriorate the material densification and ductility. Conversely, the use of a tungsten carbide grinding media leads to an extreme refinement of the milled powders, whereby alloys form a uniform microstructure with a gamma(Ni, Fe) phase configuration. This phase provides sufficient binding strength between the tungsten particles, such that the relative density and ductility of the materials were found to have been significantly enhanced. (C) 2014 Elsevier Ltd. All rights reserved.