Investigation of elastic property relationships for flake and spheroidal cast irons using Raman spectroscopy

Abstract

The deformation micromechanics of flake and spheroidal graphitic cast irons have been studied for the first time using Raman spectroscopy. It has been found that the Raman band peak positions of the graphite shift to a lower wavenumber during tensile deformation, and to a higher wavenumber in compression. The elastic properties of the cast irons have been investigated using various theoretical models. It has been shown for flake iron that the Young’s modulus is in close agreement with the models for disk-shaped inclusions, and with models for spherical inclusions for the spheroidal iron. In the case of the graphite stress at 1% strain, the same models underestimate the stress reached in the graphite possibly due to breakdown of the interface between the graphite particles and the iron matrix. It has been shown further that Raman spectroscopy can follow the elastic recovery of the cast iron and can pinpoint the onset of permanent plastic deformation by comparing the peak positions of the Raman before and after unloading.