Specimen preparation by ion beam slope cutting for characterization of ductile damage by scanning electron microscopy

Abstract

To investigate ductile damage in parts made by cold sheet-bulk metal forming a suited specimen preparation is required to observe the microstructure and defects such as voids by electron microscopy. By means of ion beam slope cutting both a targeted material removal can be applied and mechanical or thermal influences during preparation avoided. In combination with scanning electron microscopy this method allows to examine voids in the submicron range and thus to analyze early stages of ductile damage. In addition, a relief structure is formed by the selectivity of the ion bombardment, which depends on grain orientation and microstructural defects. The formation of these relief structures is studied using scanning electron microscopy and electron backscatter diffraction and the use of this side effect to interpret the microstructural mechanisms of voids formation by plastic deformation is discussed. A comprehensive investigation of the suitability of ion beam milling to analyze ductile damage is given at the examples of a ferritic deep drawing steel and a dual phase steel.

Evaluation of Void Nucleation and Development during Plastic Deformation of Dual-Phase Steel DP600

“…After ion beam slope cutting of DP600, resulting surface has a "valley-hill" topography within a range of 1 mm. [20] This relatively flat surface allows a precise evaluation of the void size, shape, and distribution. The voids with an area as small as 0.05 mm 2 can be visible at the specimen surface prepared with this method.…”

“…An ion‐etch‐plant Met‐Etch 683 from the company GATAN was used to prepare the sample's surface by using the ion beam slope cutting method for SEM‐microanalysis with the scanning electron microscope Zeiss Supra 55 VP FEG. After ion beam slope cutting of DP600, resulting surface has a “valley‐hill” topography within a range of 1 µm . This relatively flat surface allows a precise evaluation of the void size, shape, and distribution.…”