Mechanical properties in tension of mechanically attrited nanocrystalline iron by the use of the miniaturized disk bend test

Abstract

The mechanical properties of warm compacted nanocrystalline (nc) iron powder compacts of near theoretical density in the grain size range between 8 and 33 nm were investigated. The elastic and plastic behavior were characterized by miniaturized disk bend tests and hardness measurements. Light and scanning electron microscopy (SEM) were used to document the deformation and fracture morphologies. The Young's modulus of the nc Fe was essentially the same as that of coarse grained Fe. All samples failed in a macroscopically brittle manner. Local plasticity in shear bands was observed in the samples with the larger grain sizes (>20 nm). An increasing failure stress with increasing grain size is probably due to a processing effect on the flaw controlled failure of the samples. The results are discussed in the context of the deformation and fracture behavior of micrometer grain size metals and alloys.