This article presents examples of the visual fracture examination that illustrate the procedure as it applies to failure analysis and quality determination. It describes the techniques and procedures for the visual and light microscopic examination of fracture surfaces with illustrations. The article also describes microscopic and macroscopic features of the different fracture mechanisms with illustrations with emphasis on visual and light microscopy examination. The types of fractures considered include ductile fractures, tensile-test fractures, brittle fractures, fatigue fractures, and high-temperature fractures.

The reflected light microscope is the most commonly used tool to study the microstructure of metals, composites, ceramics, minerals, and polymers. For the study of the microstructure of metals and alloys, light microscopy is employed in the reflected-light mode using either bright-field illumination, dark-field illumination, polarized light illumination, or differential interference contract, generally by the Nomarski technique. This article concentrates on how to reveal microstructure properly to enable the proper identification of the phases and constituents and, if needed, measuring the amount, size, and spacing of constituents, using the light optical microscope. The discussion covers the examination of microstructures using different illumination methods and includes a comparison between light optical images and scanning electron microscopy images of microstructure.

Metallographic examination is one of the most important procedures used by metallurgists in failure analysis. Typically, the light microscope (LM) is used to assess the nature of the material microstructure and its influence on the failure mechanism. Microstructural examination can be performed with the scanning electron microscope (SEM) over the same magnification range as the LM, but examination with the latter is more efficient. This article describes the major operations in the preparation of metallographic specimens, namely sectioning, mounting, grinding, polishing, and etching. The influence of microstructures on the failure of a material is discussed and examples of such work are given to illustrate the value of light microscopy. In addition, information on heat-treatment-related failures, fabrication-/machining-related failures, and service failures is provided, with examples created using light microscopy.

This article describes testing and characterization methods of ceramics for chemical analysis, phase analysis, microstructural analysis, macroscopic property characterization, strength and proof testing, thermophysical property testing, and nondestructive evaluation techniques. Chemical analysis is carried out by X-ray fluorescence spectrometry, atomic absorption spectrophotometry, and plasma-emission spectrophotometry. Phase analysis is done by X-ray diffraction, spectroscopic methods, thermal analysis, and quantitative analysis. Techniques used for microstructural analysis include reflected light microscopy using polarized light, scanning electron microscopy, transmission electron microscopy, energy dispersive analysis of X-rays, and wavelength dispersive analysis of X-rays. Macroscopic property characterization involves measurement of porosity, density, and surface area. The article describes testing methods such as room and high-temperature strength test methods, proof testing, fracture toughness measurement, and hardness and wear testing. It also explains methods for determining thermal expansion, thermal conductivity, heat capacity, and emissivity of ceramics and glass and measurement of these properties as a function of temperature.

This article focuses on the modes of operation, physical basis, sample requirements, properties characterized, advantages, and limitations of common characterization methods that are used to evaluate the physical morphology and chemical properties of component surfaces for medical devices. The methods include light microscopy, scanning electron microscopy, atomic force microscopy, energy-dispersive x-ray spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy.

Fractography is the systematic study of fractures and fracture surfaces. It is a useful tool in failure analysis and provides a means for correlating the influence of microstructure on the fracture mode of a given material. This article discusses the preservation, preparation, and photography of fractured parts and surfaces, and describes some of the more common fractographic features revealed by light microscopy, including tensile-fracture surface marks in unnotched specimens, fatigue marks, and structural discontinuities within the metal. The article also explains how to interpret fracture information contained in optical and scanning-electron microscope fractographs.

The application of transmission electron microscope to the study of fracture surfaces and related phenomena has made it possible to obtain magnifications and depths of field much greater than those possible with light (optical) microscopes. This article reviews the methods for preparing single-stage, double-stage, and extraction replicas of fracture surfaces. It discusses the types of artifacts and their effects on these replicas, and provides information on shadowing of replicas. The article concludes with a comparison of the transmission electron and scanning electron fractographs with illustrations.

Scanning electron microscopy (SEM) has unique capabilities for analyzing fracture surfaces. This article discusses the basic principles and practice of SEM, with an emphasis on its applications in fractography. The topics include an introduction to SEM instrumentation, imaging and analytical capabilities, specimen preparation, and the interpretation of fracture features. SEM can be subdivided into four systems, namely, illuminating/imaging, information, display, and vacuum systems. The article also describes the major criteria and techniques of SEM specimen preparation, and the general features of ductile and brittle fracture modes.

This article focuses on laboratory atomic force microscopes (AFMs) used in ambient air and liquid environments. It begins with a discussion on the origin of AFM and development trends occurring in AFM. This is followed by a section on the general principles of AFM and a comprehensive list of AFM scanning modes. There is a brief description of how each mode works and what types of applications can be made with each mode. Some of the processes involved in preparation of samples (bulk materials and those placed on a substrate) scanned in an AFM are then presented. The article provides information on the factors applicable to the accuracy and precision of AFM measurements. It ends by discussing the applications for AFMs in the fields of science, technology, and engineering.

The scanning electron microscope (SEM) is one of the most versatile instruments for investigating the microscopic features of most solid materials. The SEM provides the user with an unparalleled ability to observe and quantify the surface of a sample. This article discusses the development of SEM technology and operating principles of basic systems of SEM. The basic systems covered include the electron optical column, signal detection and display equipment, and the vacuum system. The processes involved in the preparation of samples for observation using an SEM are described, and the application of SEM in fractography is discussed. The article covers the failure mechanisms of ductile failure, brittle failure, mixed-mode failure, and fatigue failure. Lastly, image dependence on microscope type and operating parameters is also discussed.

This article provides detailed information on the instrumentation and principles of the scanning electron microscope (SEM). It begins with a description of the primary components of a conventional SEM instrument. This is followed by a discussion on the advantages and disadvantages of the SEM compared with other common microscopy and microanalysis techniques. The following sections cover the critical issues regarding sample preparation, the physical principles regarding electron beam-sample interaction, and the mechanisms for many types of image contrast. The article also presents the details of SEM-based techniques and specialized SEM instruments. It ends with example applications of various SEM modes.

Transmission electron microscopy (TEM) approach enables essentially simultaneous examination of microstructural features through imaging from lower magnifications to atomic resolution and the acquisition of chemical and crystallographic information from small regions of the thin specimen. This article discusses fundamentals of the technique, especially for solving materials problems. Background information is provided to help understand basic operations and principles, including instrumentation, the physics of signal generation and detection, image formation, electron diffraction, and spectrometry techniques with data analysis.

This article discusses the fundamentals and operating principles of the following acoustic microscopy methods: scanning laser acoustic microscopy, C-mode scanning acoustic microscopy, and scanning acoustic microscopy. It describes the applications of acoustic microscopy for detecting defects in metals, ceramics, glasses, polymers, and composites with examples.

This article describes the methods and equipments involved in the preparation of specimens for examination by light optical microscopy, scanning electron microscopy, electron microprobe analysis for microindentation hardness testing, and for quantification of microstructural parameters, either manually or by the use of image analyzers. Preparation of metallographic specimens generally requires five major operations: sectioning, mounting, grinding, chemical polishing, and etching. The article provides information on the principles of technique selection in mechanical polishing, and describes the procedures, advantages, and disadvantages of electrolytic and chemical polishing. It also provides a detailed account of procedures, precautions, and composition for preparation and handling of etchants.

This article briefly discusses popular techniques for metals characterization. It begins with a description of the most common techniques for determining chemical composition of metals, namely X-ray fluorescence, optical emission spectroscopy, inductively coupled plasma optical emission spectroscopy, high-temperature combustion, and inert gas fusion. This is followed by a section on techniques for determining the atomic structure of crystals, namely X-ray diffraction, neutron diffraction, and electron diffraction. Types of electron microscopies most commonly used for microstructural analysis of metals, such as scanning electron microscopy, electron probe microanalysis, and transmission electron microscopy, are then reviewed. The article contains tables listing analytical methods used for characterization of metals and alloys and surface analysis techniques. It ends by discussing the objective of metallography.

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.

Nanotechnology and smart-coating technologies have been reported to show great promise for improved performance in critical areas such as corrosion resistance, durability, and conductivity. This article exemplifies nanofilms and nanomaterials used in coatings applications, including carbon nanotubes, silica, metals/metal oxides, ceramics, clays, buckyballs, graphene, polymers, titanium dioxide, and waxes. These can be produced by a variety of methods, including chemical vapor deposition, plasma arcing, electrodeposition, sol-gel synthesis, and ball milling. The application of nanotechnology and the development of smart coatings have been dependent largely on the availability of analytical and imaging techniques such as Raman spectroscopy, scanning and transmission electron microscopy, atomic force microscopy, and scanning tunneling microscopy.

This article discusses the preparation of photomacrographs of fracture surfaces. It provides useful information on the equipment used, such as view cameras, 35-mm single-lens-reflex cameras, and stereomicroscopes. The article describes the role of lenses, focusing, camera magnification, and selection of lens aperture in a microscopic system. It illustrates the lighting techniques employed in photography and highlights the use of different films. The article concludes with a list of auxiliary equipment used in fracture surface photography.

Failure analysis is an investigative process that uses visual observations of features present on a failed component fracture surface combined with component and environmental conditions to determine the root cause of a failure. The primary means of recording the conditions and features observed during a failure analysis investigation is photography. Failure analysis photographic imaging is a combination of both science and art; experience and proper imaging techniques are required to produce an accurate and meaningful fracture surface photograph. This article reviews photographic principles and techniques as applied to failure analysis, both in the field and in the laboratory. The discussion covers the processes involved in field and laboratory photographic documentations, provides a description of professional digital cameras, and gives information on photographic lighting and microscopic photography. Special techniques can be employed to deal with highly reflective conditions and are also described in this article.

This article introduces the principles of Raman spectroscopy and the representative materials characterization applications to which Raman spectroscopy has been applied. A discussion on light-scattering fundamentals and a description of the experimental aspects of the technique are included. Emphasis is placed on the different instrument approaches that have been developed for performing Raman analyses on various materials. The applications presented reflect the breadth of materials characterization uses for Raman spectroscopy and highlight the analysis of bulk material and of surface and near-surface species.