Search Results for electron probe microanalyzers

Electron probe microanalysis (EPMA) makes it possible to combine structural and compositional analysis in one operation. This article describes the basic concepts of microanalysis and the processing of EPMA that involves the measurement of the characteristic X-rays emitted from a microscopic part of a solid specimen bombarded by a beam of accelerated electrons. It provides information on the various aspects of energy-dispersive spectrometry (EDS) and wavelength-dispersive spectrometry (WDS), and elucidates the qualitative analysis of the major constituents of EDS and WDS. The article includes information on the analog and digital compositional mapping of elemental distribution, and describes the strengths and weaknesses of WDS and EDS spectrometers in X-ray mapping. It also outlines the application of EPMA for solving various problems in materials science.

Microstructural analysis is the combined characterization of the morphology, elemental composition, and crystallography of microstructural features through the use of a microscope. This article reviews three types of the most commonly used electron microscopies in metallurgical studies, namely scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy. It briefly describes the operating principles, instrumentation which includes energy dispersive X-ray detectors, spatial resolution, typical use of the techniques, elemental analysis detection threshold and precision, limitations, sample requirements, and the capabilities of related techniques.

This article discusses the capabilities and limitations of various material characterization methods that assist in the selection of a proper analytical tool for analyzing particulate materials. Commonly used methods are microanalysis, surface analysis, and bulk analysis. The techniques used for performing microanalysis include scanning electron microscopy and electron probe X-ray microanalysis. The article describes surface analysis techniques, including Auger electron spectroscopy, X-ray photoelectron spectroscopy, and ion-scattering spectroscopy. Bulk analysis techniques, such as X-ray powder diffraction, inductively coupled plasma atomic emission spectroscopy, atomic absorption spectroscopy, and atomic fluorescence spectrometry, are also discussed.

This article focuses on the visual or macroscopic examination of damaged materials and interpretation of damage and fracture features. Analytical tools available for evaluations of corrosion and wear damage features include energy dispersive spectroscopy, electron probe microanalysis, Auger electron spectroscopy, secondary ion mass spectroscopy, and X-ray powder diffraction. The article discusses the analysis and interpretation of base material composition and microstructures. Preparation and examination of metallographic specimens in failure analysis are also discussed. The article concludes with a review of the evaluation of polymers and ceramic materials in failure analysis.

Examination of a damaged component involves a chain of activities that, first and foremost, requires good observation and documentation. Following receipt and documentation, the features of damage can be recorded and their cause(s) investigated, as this article briefly describes, for typical types of damage experienced for metallic components. This article discusses the processes involved in visual or macroscopic examination of damaged material; the interpretation of fracture features, corrosion, and wear damage features; and the analysis of base material composition. It covers the processes involved in the selection of metallurgical samples, the preparation and examination of metallographic specimens in failure analysis, and the analysis and interpretation of microstructures. Examination and evaluation of polymers and ceramic materials in failure analysis are also briefly discussed.

Analytical transmission electron microscopy (ATEM) is unique among materials characterization techniques as it enables essentially the simultaneous examination of microstructural features through high-resolution imaging and the acquisition of chemical and crystallographic information from small regions of the specimen. This article illustrates the effectiveness of the technique in solving materials problems. The first section of the article provides information on analytical electron microscope (AEM) and its basic operational characteristics as well as on electron optics, electron beam/specimen interactions and the generation of a signal, signal detectors, electron diffraction, imaging, x-ray microanalysis, electron energy loss spectroscopy, and sample preparation. The second section consists of 12 examples, each illustrating a specific type of materials problem that can be solved, at least in part, with AEM.

Scanning electron microscopy (SEM) has shown various significant improvements since it first became available in 1965. These improvements include enhanced resolution, dependability, ease of operation, and reduction in size and cost. This article provides a detailed account of the instrumentation and principles of SEM, broadly explaining its capabilities in resolution and depth of field imaging. It describes three additional functions of SEM, including the use of channeling patterns to evaluate the crystallographic orientation of micron-sized regions; use of backscattered detectors to reveal grain boundaries on unetched samples and domain boundaries in ferromagnetic alloys; and the use of voltage contrast, electron beam-induced currents, and cathodoluminescence for the characterization and failure analysis of semiconductor devices. The article compares the features of SEM with that of scanning Auger microscopes, and lists the applications and limitations of SEM.

Homogenization, in a broad sense, refers to the processes designed to achieve uniform distribution of solutes or phases in a given matrix. This article addresses the root cause for inhomogeneities in cast components. It is nearly a standard industrial practice to homogenize alloys before thermomechanical processing. The article lists the objectives of homogenization and benefits of homogenization treatments. The benefits include increased resistance to pitting corrosion, increased resistance to stress-corrosion cracking, improved ductility, and uniform precipitate distribution during subsequent aging. The article provides a schematic illustration of an energy-dispersive X-ray spectroscope (EDS) scattered data of solute distributions across a dendrite due to microsegregation of chromium and molybdenum. It concludes with information on the computational modeling for simulation of microsegregation of chromium and molybdenum.

This article discusses the advantages and disadvantages of field metallography and describes the important material characteristics and other aspects to be considered before performing any metallographic procedure. It investigates the various stages of sample preparation in the metallographic laboratory: grinding, polishing, etching, preparing a replica, and obtaining a small sample. The article also illustrates the applications of field metallography with case studies.

This article discusses fractures and cracks due to ancient artifact weaknesses. It provides several case studies to aid the appreciation of fractography as a diagnostic technique and to understand the importance of cracking. These case histories concern ancient gold and silver alloys, bronzes, and wrought irons. The article considers the applicabilities of fractography, metallography, and chemical analyses in answering archaeological and archaeometallurgical questions. The article also discusses the restoration and conservation of corroded and embrittled artifacts, including the use of coatings.

This article describes the microstructure and metallographic practices used for medium- to high-carbon steels as well as for low-alloy steels. It explains the microstructural constituents of plain carbon and low-alloy steels, including ferrite, pearlite, and cementite. The article provides information on how to reveal the various constituents using proven metallographic procedures for both macrostructural and microstructural examination. Emphasis is placed on the specimen preparation procedures such as sectioning, mounting, grinding, and polishing. The article illustrates the use of proven etching techniques for plain carbon and low-alloy steels.

This article illustrates how objective experiments and comparisons can be used to develop surface preparation procedures for metallographic examination of structural features of metals. These procedures are classified as machining, grinding and abrasion, or polishing. The article describes the abrasion artifacts in austenitic steels, zinc, ferritic steels, and pearlitic steels, and other effects of abrasion damages, including flatness of abraded surfaces and embedding of abrasive. Different polishing damages, such as degradation of etching contrast and scratch traces, are reviewed. The article explains the final-polishing processes such as skid polishing, vibratory polishing methods, etch-attack and electromechanical polishing, and polishing with special abrasives. An overview of special polishing techniques for unusual materials such as very hard and very soft materials is provided. The article concludes with a discussion on semiautomatic preparation procedures, providing information on procedures based on the use of diamond abrasives charged in a carrier paste and in a suspension.

This article reviews various phases and constituents found in the microstructures of low-carbon and coated steels. It provides information on the criteria for selecting proper metallographic procedures. Techniques used to prepare metallographic specimens of low-carbon steels and coated steels, such as sectioning, mounting, grinding, polishing, and etching, are discussed. The article also reviews the simple and proven manual sample preparation techniques of coated steel specimens.

Mounting of the specimen is often desirable or necessary for handling and metallographic polishing after the specimen is cut into an appropriate size. This article illustrates the different mechanical clamps used in mounting small specimens. It provides useful information on compression molded mounts, which are molded with thermoplastic and thermosetting resins. The article reviews several resins and their key factors, which help in the selection of the most appropriate mounting method and resin. It also discusses the characteristics of plastic mounting materials. The article provides information on the molds and resins used for castable mounts, vacuum treatment of mounts, special mount arrangements, and mount marking and storage.

This article is a compilation of definitions for terms related to engineering materials, including plastics, elastomers, polymer-matrix composites, adhesives and sealants, ceramics, ceramic-matrix composites, glasses, and carbon-carbon composites.