Volume 61, Issue 12

The metallographic revelation of the microstructure of very thin wires and foils is a challenging task. How can a cross-section and a longitudinal section be prepared from a 36 μm thin wire? Or how can a flat section of a weld on 125 μm thin Nitinol sheets be successfully prepared? The preparation is to always allow for representing the crystal orientation by EBSD. Can this be achieved relying on the classical preparation of sections or do newer methods have to be used? This article presents the possibilities of a classical preparation and ion beam polishing.

The paper will explain the formation and effects of brittle precipitates in form of borides and silicides during high-temperature vacuum diffusion brazing on the example of a nickel-based filler metal from the NiCrSiB system. This filler metal foil was used to braze butt joints of the metastable austenite AISI 304L. Energy and wavelength dispersive X-ray spectroscopy was applied to identify the precipitates. Using a focused ion beam in scanning electron microscopy, the brazed joint was removed layer by layer over a large area to gain insights into the 3D structure of the precipitates. Subsequently, a methodology will be presented on how to reconstruct a 3D model from the image data using deep learning-based image segmentation. The final model unravels the complex morphology of these precipitates and thus contributes to a better understanding of the solidification and precipitation mechanisms in diffusion brazing.

Hot pressing of titanium and carbon steel leads to the formation of a diffusion layer at the interface. Depending on the carbon content of the steel used, it either exclusively contains TiC or additional other phases. In the case of steel with a medium carbon concentration (0.67 wt.% C), a pure TiC layer forms. A preparation methodology was developed to make statements about functional and microstructural properties of the respective layers such as layer thickness, porosity, or grain size. However, apart from the diffusion layer’s microstructure, it also reveals the microstructure of the two base substrates. A comparison based on electron backscatter diffraction (EBSD) examinations yields similar results in terms of microstructure. A micrograph analysis based on the new preparation methodology also allows confirming the element distribution measurement by glow discharge optical emission spectroscopy (GDOES). The methodology therefore provides a way of quickly and reliably controlling the layer formation during the hot pressing process of titanium and carbon steel.

The aim of this study is to demonstrate differences in the manufacturing of twin wire mesh panels for fencing systems. To this end, twin wire mesh panels made of S235JR and of identical and different dimensions were received from different manufacturers for comparison and in order to reveal differences resulting from the manufacturing process. The quality of the panels was evaluated using light optical microscopy, Vickers hardness tests, scanning electron microscopy as well as tensile tests. Differences in the structure of the weld will be demonstrated by means of metallographic sections and hardness profiles. The zinc coatings deposited by different processes for corrosion protection were characterized by coating thickness measurements on cross sections, light optical microscopy and energy dispersive X-ray spectroscopy (EDS) measurements. Tensile tests using a specially developed clamping device were performed in order to draw conclusions on the durability of the welds.