Mechanical properties of nanostructured and ultrafine-grained iron alloys produced by spark plasma sintering of ball milled powders

Abstract 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 10 μm), 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 (30–60 MPa) 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.