Abstract Two α-β brass alloys with varying Zn contents have been studied. The samples received for examination were heat-treated at 500 °C in order to conduct dezincification studies according to EN ISO 6509-1 and to measure the depth of dezincification from metallographic sections. According to the phase diagram, the α-phase content should increase as a result of heat-treatment at 500 °C. This phenomenon, however, is difficult to observe in the metallographic sections which were prepared from the heattreated samples. When analyzing the depth of dezincification, it was found that reduced dezincification occurred in the heat-treated samples. This is plausible since β brass is attacked by preferential corrosion. Not only was uniform layer dezincification observed in the brass alloy with the higher Zn content, but also the onset of plug dezincification. This is associated with the original microstructure of the brass which is characterized by a coarse primary grain size. In this alloy, it is clearly observed that larger areas containing alpha brass will impede the process of dezincification.

Article Eine neue Ära des metallografischen Ätzens – Von der wissenschaftlichen Idee zum Serienprodukt „ThEtching“ was published on September 1, 2023 in the journal Practical Metallography (volume 60, issue 9).

Abstract Steels with different mechanical and chemical properties are used together in the oil and gas industry. In this case, it has brought about the necessity of joining steels with different properties by welding. Most of the time, there are problems in welding these steels with different chemical properties. Therefore, in this study, AISI 304 stainless steel, AISI 4140 tempered steel, and S235JR structural steel with different chemical and mechanical properties used in the oil and gas industry were joined by friction welding. Then, macro and microstructure studies as well as hardness measurements, tensile tests, and torsion tests were applied to the produced samples. As a result of the micro-structure studies, it was observed that the martensitic structure was formed in the full deformation region of the joint made of AISI 304 stainless and AISI 4140 tempered steel, while it was determined that the other joints were formed of recrystallized fine grains in the full deformation region with the effect of friction. When the hardness measurement results were examined, it was determined that the hardest region was the full deformation region in all welded joints produced. As a result of the tensile tests, the highest tensile strength obtained was 622.94 N/mm2 in the joint made of AISI 304 stainless steel and AISI 4140 tempered steel. As a result of the torsion tests, the highest torsion moment was measured as 250 Nm in the sample produced from AISI 304 stainless steel and AISI 4140 tempered steel.

Abstract For a comprehensive microstructural characterization of welds, a scale-bridging analysis of the microstructure is required. It is the only way to identify all microstructural characteristics relevant for the mechanical properties which, in turn, may cover several observation scales. The analytical methods used range from etchings for the macroscopic evaluation of the weld and heat-affected zone to the detection of so-called “local brittle zones” (LBZs) in the micrometre range. This paper will study weld joints in low-alloy steels produced by multi-wire submerged arc welding and electron beam welding. Macro and micro etching as well as electropolishing will be used for microstructural contrasting. Scanning electron microscopy will be performed to identify the finely dispersed carbon-rich secondary phase. Electron backscatter diffraction will enable the identification of so-called martensite/austenite regions (MAs) capable of acting as LBZs.

Abstract The influence of vibratory polishing time on the quality of EBSD mappings of a multiphase microstructure is investigated and optimized for CuZn30//CuZn80 diffusion couples. The diffusion couples consist of four different phases whose hardness varies between 70 HV0.1 and 454 HV0.1. These are first mechanically ground, polished and finally prepared by vibratory polishing. A vibratory polishing of 2 h provides for all phases the highest quality of the recorded Kikuchi patterns (Image Quality values) and the highest correct assignment of the individual pixels of the mapping. Preparation artifacts, such as relief formation, only appear at higher vibratory polishing times (> 2 h). A vibratory polishing of the diffusion couples of 0.5 h already provides sufficient surface quality for EBSD analyses.

Abstract A Hallstatt period burial mound (tumulus) in Schandorf, Burgenland, Austria, was opened and archaeologically investigated in 2021. Not only numerous pottery fragments, but also some garment buttons were found, one of which was provided for metallographic examinations, aiming at identifying the method of manufacture: soldering, riveting, casting? Prior to the metallographic examinations, micro-computed tomography (μm CT) was carried out at a resolution of 5 μm. The Figures show that large areas are oxidized. It was, however, found that metallic portions still existed. The overall appearance suggests investment casting as the manufacturing method. Analytical measurements revealed that the material is tin bronze. Despite severe corrosion, the metallographic sections still exhibit a clearly recognizable cast structure. There are presumably two types of corrosion: first, high temperature corrosion, which resulted in the formation of bronze oxides in the grain boundary areas during the cremation, and, second, corrosion in an aqueous environment, during which malachite formed. So far, no comparable studies can be found in the literature.

Abstract A metallographic section from the crack area of an exhaust gas turbocharger was supplied by the customer. The shaft made of quenched and tempered low-alloy steel and the charger wheel made of a nickel-based superalloy were joined by laser welding. For design reasons, the root side of the weld contained a geometric notch, at which a high cycle fatigue crack initiated during the test facility operation of the turbocharger. At the time of examination, it went through almost the entire weld root. As a corrective action, it was recommended that the welded joint be replaced by a shrink fit.

Abstract The prior austenite grain size (PAGS) represents one of the most significant microstructural parameters for steel research and process development. Since the PAGS directly correlates with recrystallisation during rolling in the manufacturing process of steel plates, it has a huge influence on its mechanical properties. Methods to determine the PAGS reliably and reproducibly are in high demand. There are several different approaches, based on different working principles, aiming to measure the PAGS. In this paper, the focus will be held on chemical etching methods because they allow, other than indirect techniques, space-resolved images as output, coupled with a fast application with good statistics and do not necessarily require a pretreatment of the specimen that can alter properties of interest. A parameter study has been conducted to identify unknown influencing variables as well as to tune well known parameters for their application to low-carbon steels. In the scope of this work, a novel and objective way of determining the PAGS is being presented. A reproducible approach has been developed that is able to automatically reconstruct the prior austenite grain boundaries (PAGB) from low-carbon steels and thereby determining the PAGS. Based on an improved etching recipe, a routine could be elaborated using modern methods of machine learning in the field of computer vision that is able to quantitatively analyze optical micrographs. Semantic segmentation is used to detect the PAGB based on correlative EBSD data and expert’s annotations; thus, reconstructing the prior morphological microstructure. Therefore, besides the determination of the average grain size, the distribution of the PAGS and their morphological parameters can be quantified.