Reduction of porosity in oxide dispersion-strengthened alloys produced by powder metallurgy

In this work, the porosity in a iron-based oxide dispersion-strengthened (ODS) alloy, namely, PM2000, has been studied together with its recrystallization behavior. It has been found that pores are only found in coarse secondary recrystallized grains formed at the early stage of recrystallization. It is suggested that a lack of fast diffusion paths, particularly grain boundaries, will prevent gas trapped in the materials during mechanical alloying (MA) from diffusing away, and porosity is formed as a result. Thus, it is proposed that an extended anneal below the secondary recrystallization temperature will help to reduce the subsequent evolution of porosity in these materials, and the method has been demonstrated to work successfully in PM2000.