Mechanical properties of nanostructured and ultra fine-grained iron alloys produced by Spark Plasma Sintering of ball milled powders

Spark plasma sintering of an iron-based powder has been studied. The powder was prepared with three different microstructures: fully annealed (grain size d larger than 10m), nanometer sized (d ∼30 nm) and nanometer sized with silica nanoparticles along grain boundaries (d ∼20 nm). Spark plasma sintering was carried out at varying pressure (30–60MPa) and temperature (from 800 to 900 ◦C). Shrinkage during sintering was studied by means of densification curves. Near fully dense or fully dense samples were consolidated; depending on the sintering temperature and on thermal stability of the powder, nanostructured, ultrafine-grained and fine grained materials were obtained. Tensile testing demonstrates that the finer the microstructure, the harder and the stronger is the material, and the lower is the uniform deformation.