A. Herges, C. Pauly, M. Müller, D. Britz, F. Mücklich
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.
{"title":"Scale-bridging contrasting and characterization of multi-wire submerged arc welds and electron beam welds in steels","authors":"A. Herges, C. Pauly, M. Müller, D. Britz, F. Mücklich","doi":"10.1515/pm-2022-1041","DOIUrl":"https://doi.org/10.1515/pm-2022-1041","url":null,"abstract":"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.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88735465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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.
{"title":"Vibratory polishing of multiphase CuZn30//CuZn80 diffusion pairs for electron backscatter diffraction (EBSD) characterization","authors":"J. Möbius, S. Lippmann, M. Seyring","doi":"10.1515/pm-2023-1043","DOIUrl":"https://doi.org/10.1515/pm-2023-1043","url":null,"abstract":"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.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90587735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Herges, L. Ulrich, S. Scholl, M. Müller, D. Britz, F. Mücklich
Abstract The characterization of fractographic surfaces typically requires experts to evaluate the characteristics of fracture surfaces. However, these evaluations are influenced by human factors, such as subjectivity, and suffer from a lack of reproducibility. In this context, machine learning (ML), which has been established in various disciplines within materials science over the past few years, is a promising field enabling a more objective and reproducible evaluation. This study will evaluate the use of ML for the evaluation of fracture surfaces of notched Charpy specimens based on digital camera images. Image sections of the two reference regions “upper shelf” (ductile) and “lower shelf” (brittle) will serve as the database. In a first step, data visualization will be performed and data separability will be verified using unsupervised ML. On this basis, supervised ML will be used to train models to distinguish brittle and ductile fractures. These models will then be applied to determine ductile und brittle portions in mixed fracture modes, with the results being in good agreement with the expert consensus achieved in the round robin test.
{"title":"Machine learning for the classification of macroscale fracture surfaces","authors":"A. Herges, L. Ulrich, S. Scholl, M. Müller, D. Britz, F. Mücklich","doi":"10.1515/pm-2023-1042","DOIUrl":"https://doi.org/10.1515/pm-2023-1042","url":null,"abstract":"Abstract The characterization of fractographic surfaces typically requires experts to evaluate the characteristics of fracture surfaces. However, these evaluations are influenced by human factors, such as subjectivity, and suffer from a lack of reproducibility. In this context, machine learning (ML), which has been established in various disciplines within materials science over the past few years, is a promising field enabling a more objective and reproducible evaluation. This study will evaluate the use of ML for the evaluation of fracture surfaces of notched Charpy specimens based on digital camera images. Image sections of the two reference regions “upper shelf” (ductile) and “lower shelf” (brittle) will serve as the database. In a first step, data visualization will be performed and data separability will be verified using unsupervised ML. On this basis, supervised ML will be used to train models to distinguish brittle and ductile fractures. These models will then be applied to determine ductile und brittle portions in mixed fracture modes, with the results being in good agreement with the expert consensus achieved in the round robin test.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88577210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Picture of the Month","authors":"","doi":"10.1515/pm-2023-0032","DOIUrl":"https://doi.org/10.1515/pm-2023-0032","url":null,"abstract":"","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134903806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The failure of fastening elements in electrical terminal blocks was attributed to various material-related causes. While the casehardened terminal screws broke due to hydrogen embrittlement, the material-related cause of the plastic deformations of the roof-shaped washers and the stripping of the threads of the square nuts are undersizing and an insufficient strength for this particular application.
{"title":"Failure of Connecting Clamps in Electrical Terminal Blocks","authors":"A. Neidel, B. Fischer, M. Giller","doi":"10.1515/pm-2023-0031","DOIUrl":"https://doi.org/10.1515/pm-2023-0031","url":null,"abstract":"Abstract The failure of fastening elements in electrical terminal blocks was attributed to various material-related causes. While the casehardened terminal screws broke due to hydrogen embrittlement, the material-related cause of the plastic deformations of the roof-shaped washers and the stripping of the threads of the square nuts are undersizing and an insufficient strength for this particular application.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83142282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Picture of the Month","authors":"","doi":"10.1515/pm-2023-0026","DOIUrl":"https://doi.org/10.1515/pm-2023-0026","url":null,"abstract":"","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135463596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Transverse through-wall airfoil cracking was found in a row 3 twin turbine vane segment of a type used in heavy-duty gas turbine engines for power generation. A laboratory investigation determined liquation cracking (LC), a hot cracking mechanism, as the metallurgical cause of failure. As became apparent only after the investigation, the root cause of failure was a malfunctioning plasma gun used for thermal spraying the thermal barrier ceramic top coat onto the subject part.
{"title":"Liquation Cracking in Row 3 Twin Turbine Vane Segment Caused by Malfunctioning Plasma Coating Gun","authors":"A. Neidel, B. Fischer, T. Gädicke, T. Ullrich","doi":"10.1515/pm-2023-0025","DOIUrl":"https://doi.org/10.1515/pm-2023-0025","url":null,"abstract":"Abstract Transverse through-wall airfoil cracking was found in a row 3 twin turbine vane segment of a type used in heavy-duty gas turbine engines for power generation. A laboratory investigation determined liquation cracking (LC), a hot cracking mechanism, as the metallurgical cause of failure. As became apparent only after the investigation, the root cause of failure was a malfunctioning plasma gun used for thermal spraying the thermal barrier ceramic top coat onto the subject part.","PeriodicalId":20360,"journal":{"name":"Practical Metallography","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85855946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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