NIST Advanced Manufacturing Series 100-3

Microstructure Analysis for Additive 

Manufacturing: A Review of Existing 

Standards

Christopher U. Brown

Alkan Donmez

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http://dx.doi.org/10.6028/NIST.AMS.100-3
NIST Advanced Manufacturing Series 100-3

Microstructure Analysis for Additive 

Manufacturing: A Review of Existing 

Standards

Christopher U. Brown

Systems Integration Division

Engineering Laboratory

Alkan Donmez

Intelligent Systems Division

Engineering Laboratory

This publication is available free of charge from:

http://dx.doi.org/10.6028/NIST.AMS.100-3

September 2016

U.S. Department of Commerce 

Penny Pritzker, Secretary

National Institute of Standards and Technology 

Willie May, Under Secretary of Commerce for Standards and Technology and Director 
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Introduction

Metal-based additive manufacturing (AM) offers unique possibilities to fabricate 

metal parts with complex structures. Due to the very rapid melting and solidifying of thin 

layers of metal at a time, the nature of the material resulting from the AM process has 

unique characteristics. The National Institutes of Standards and Technology (NIST) 

project Characterization of Additive Manufacturing Materials aims to develop new 

methods to characterize additively manufactured materials or to expand existing methods 

applicable for other materials. 

Understanding the microstructure of AM materials, i.e. parts made by AM 

processes, is important for industry to have confidence in AM parts. The focus of this 

report is to assess the existing microstructure standards for metals to determine if the 

existing standards are sufficient for characterizing AM metals. 

Scope

Microstructures of all materials, including additively manufactured materials, are 

significantly affected by various process parameters, manufacturing strategies, post 

process heat treatments, and environmental conditions, resulting in varying mechanical 

and material properties. Traditional metallography techniques are used to quantify these 

microstructures to better understand the effects of multiple factors. The purposes of this 

investigation are to review existing standards describing the methodologies for 

microstructure characterization of metallic materials, consider their applicability to 

additively manufactured metal alloys, and identify, if any, new standards addressing 
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unique characteristics of such AM materials. This report provides a summary of this 

review and provides recommendations for applying the existing and potential future 

standards to additively made materials.

In order to perform an assessment of the existing standards related to metal 

microstructure and determine their applicability to AM metals, a number of standards 

were reviewed. ASTM and ISO standards were primarily surveyed. Since there are 

multiple features describing the metal microstructure, a summary is provided of the 

standards related to each feature with increasing level of microstructure, organized from a 

micro-level to a more macro-level. Most techniques to analyze metal microstructure 

require some type of imaging of the specially prepared sample surface. The imaging 

techniques found in the reviewed standards are optical microscopy, Scanning Electron 

Microscopy (SEM), x-ray diffraction (XRD), and electron backscatter diffraction 

(EBSD). There are also non-destructive evaluation techniques found in the standards for 

characterizing microstructure, which are also summarized in this report. 

Microstructures of metallic materials include the following features:

1. Crystal structure - lattice parameters

2. Grain size and grain boundaries

3. Orientation effects - texture

4. Material phases - volume fraction of phase constituents

5. Material phases – precipitates and inclusions

6. Voids, microcracks and delaminations
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Microstructure characterization methods require sampling of parts or specific test 

specimens using special preparation methods. Such preparation methods may include 

cross-sectioning, grinding, polishing, and etching. There are specific standards 

describing these methods. These standards are summarized in Table 1.

Table 1. Summary of standards describing methods to characterize material 

microstructural features

Microstructural features Relevant standards

Crystal structure - lattice parameters No standards found

Grain size and grain boundaries ASTM E112, ASTM E930, ASTM E1181, 

ASTM E1382, ASTM E2627, ISO 643, ISO 

2624, ISO 4499-2, ISO 14250

Orientation effects - texture ASTM E82

Material phases - volume fraction of 

phase constituents

ASTM E562, ASTM E975, ASTM E1245, 

ASTM E1268, ISO 9042

Material phases – precipitates and 

inclusions

ASTM E45, ASTM E1245, ASTM E2142, 

ASTM E2283, ISO 4967

Voids, microcracks and delaminations ASTM E3, ASTM E165, ASTM E543, 

ASTM E1208, ASTM E1209, ASTM E 

1210, ASTM E1219, ASTM E1220, ASTM 

E1418, ASTM E2297, ISO 4505, ISO 4494-

4,
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In general, all of the following standards appear to be capable of addressing AM 

manufactured materials. Therefore, we will not address the applicability how each 

individual standard applies to AM materials. Rather, we will discuss in the conclusion a 

few specific concerns that the AM community should consider when applying existing 

microstructure standards to AM metals. 

1. Crystal structure - lattice parameters

A crystal structure is the three dimensional ordered arrangement of atoms, ions, or 

molecules in a solid material. The crystal lattice is the array of sites where atoms sit, 

repeating in all directions that represents the crystal structure. The unit cell is the smallest 

unit of volume that contains all the structural and symmetry information to build the solid 

structure. Lattice parameters include the length along the edge of a unit cell and the 

angles of the sides of the unit cell. The crystal structure can be described by its unit cell. 

A unit cell may contain one or more lattice points, and each lattice point may contain one 

or more atoms. Three common cubic crystals include the simple cubic, body-centered 

cubic (BCC), and face-centered cubic (FCC) structures.

There does not appear to be microstructural metal standards that address how to 

characterize structural features at this level. Per the ASM Handbook (Metals Handbook 

9th Edition, ASM), a common instrument that is often used is the transmission electron 

microscope (TEM) to image lattice defects and precipitates. The TEM technique uses a 

beam of electrons passing through a thin specimen. The electron beam interacts with the 
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specimen to form an image or pattern which is captured on a screen or detector (Ruhle, 

1985).

2. Grain size and grain boundaries 

Grain boundaries are defects in the crystal structure and the interfaces where 

crystals of different orientations meet. Grain boundaries can disrupt dislocations through 

a material so that reducing the grain size can improve strength. Crystals, or grains, form 

during the cooling of materials. Their degree of orientation is referred to as texture. A 

grain boundary is the interface at which two grains meet. A grain boundary is a single 

phase interface, where the crystals on either side are identical except with respect to 

orientation. Grain boundaries may contain atoms moved from their original lattice site, 

dislocations, and impurities that have migrated to a grain boundary to lower its energy. 

The higher energy associated with an interfacial excess energy of grain boundaries makes 

them a potential site for the nucleation of new phases from the solid. 

There are several standards that are related to techniques and instruments for grain 

size measurements. Several ASTM and ISO standards discuss methods to determine 

various measurements of grain size, including average grain size (ASTM E112, ISO 643, 

ISO 4499-2, ISO 2624, ASTM E1382, and ASTM E2627), largest grain size (ASTM 

E930), and characterizing duplex grain sizes (ASTM E1181, ISO 14250). “Duplex grain 

sizes” are defined as a distribution of grain sizes that are not a single log normal 

distribution after applying the measurement methods defined in ASTM E112. 
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ASTM E112 and ISO 643 focus on characterizing grain size using a reflected 

light microscope using three different procedures: comparison to standard charts to 

measure grain size, determining the number of grains per unit area, and intercept of 

grains or grain boundaries with a straight line of known length. These procedures apply 

to the single phase grain structures but can also be applied to determine the average size 

of a particular grain structure in a multiphase or multi-constituent specimen.

ASTM E1382 describes a test method for determining average grain size using a 

reflected light microscope and semiautomatic and automatic image analysis. Grain size 

measurements are determined from the intercept of a straight line of known length and 

individual grains and grain boundaries, measurements of grain boundary lengths and 

grain areas. The selection of specimen orientation and location is important and discussed 

in detail in ASTM E3. 

ASTM E2627 describes how to determine average grain size using electron 

backscatter diffraction (EBSD). EBSD involves placing a crystalline specimen in a 

scanning electron microscope (SEM). Electrons are diffracted back out of the specimen 

and strike a phosphor screen producing a pattern of intersecting bands. From this 

diffraction pattern, crystal structure and orientation can be determined as a function of 

position on the samples surface.

A standard test method for estimating the largest grain observed in a 

metallographic section using a microscope is described in ASTM E930. However this 

procedure is intended for microstructures containing outlier coarse grains, where their 

population is too sparse for grain size determination by ASTM E112. 
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ASTM E1181 is a test method for the specific case of determining if a duplex 

grain size exists. ISO 14250 also addresses characterizing duplex grain sizes. The use of 

the term duplex does not imply that only two grain size distributions exist. The test 

methods separate duplex grain sizes into two classes (randomly varying, and 

topologically varying), and define specific types of duplex grain sizes within these 

classes. Examples of randomly intermingled grain sizes include: isolated coarse grains in 

a matrix of much finer grains, extremely wide distributions of grain sizes, and bimodal 

distribution of grain size. Examples of topological duplex grain sizes include: systematic 

variation of grain size across the section of a product, necklace structures, banded 

structures, and grain growth in selected areas of critical strain. 

3. Orientation effects – texture

Texture is the distribution of the crystallographic orientations of the grains that 

make up a microstructure. A material with a random distribution in the orientation of its 

grains is classified as having no texture. A substance with a certain degree of orientation 

is classified as having weak, moderate or strong texture. 

ASTM E82/E82M describes the back-reflection Laue procedure used to 

determine the orientation of a metal crystal. An incident beam from the x-ray source 

passes through a pinhole aperture, strikes the specimen crystal structure, and is diffracted 

back to the detector located between the x-ray source and the specimen. The detector 

shows a pattern of white spots which are the x-ray beams diffracted by the atomic planes 

within the specimen crystals. The pattern of white spots and their positions in space are 
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used to compare to standard stereographic projections of crystals to determine the crystal 

orientation. 

4. Material phases - volume fraction of phase constituents

Determining a volume fraction of a constituent or phase by systematic manual 

point count method is described in ASTM E562 and ISO 9042 using a light microscope 

or SEM with a point grid. Two common grid arrangements, a circular or square array, are 

typically used. Although this is a manual method, similar characteristics can be 

determined using the automatic method described in ASTM E1245. A test grid is 

superimposed over an image produced by a light microscope, SEM, or micrograph. The 

number of test points is counted that fall within the phase or constituent of interest. 

Samples selected should be representative of the general microstructure at a specified 

location within a lot, heat, or part. 

Volume percent of retained austenite phase in steel using integrated intensities 

(area under the peak above background) of X ray diffraction peaks using chromium and 

molybdenum x ray radiation is described in ASTM E975. The method applies to carbon 

and alloy steels with near random crystallographic orientations of both ferrite and 

austenite phases. Retained austenite with a near random crystallographic orientation is 

found in the microstructure of heat-treated low-alloy, high-strength steels that have 

medium or higher carbon contents. Although retained austenite may not be evident in the 

microstructure, its presence can have significant effects on material and mechanical 

properties, performance during service, wear resistance, and corrosion behavior. 
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ASTM E1268 describes procedures to qualitatively characterize the appearance of 

banded structures, procedures for characterizing the extent of banding, and a microindentation hardness procedure for determining the difference in hardness between bands 

in heat treated specimens. Banding is the segregation of elements into distinct layers 

during solidification. Microstructural banding or orientation can affect the mechanical 

properties of a material. These methods are described to measure the number of bands per 

unit length, the inter-band or inter-particle spacing and the degree of anisotropy or 

orientation. Stereological measurements are made by superimposing a test grid on a 

projected image from a reflected-light microscope.

5. Material phases – precipitates and inclusions 

Inclusions are foreign particles that may be contained in the grain boundaries 

between grains, may be non-metallic particles, and can affect the mechanical properties 

of a solid. Characterizing the inclusion content in a material is therefore important. There 

are several standards that describe methods to count different types of inclusions. 

Precipitates are secondary phases within a microstructure, and are often used as a 

strengthening mechanism. Typically the precipitates will increase a metals strength or 

hardness by preventing the movement of dislocations or defects in a crystal’s lattice 

structure.

ASTM E45 describes test methods for determining the nonmetallic inclusion 

content in wrought steel or other alloys. Methods using a light microscope characterize 

inclusion size, shape, concentration, and distribution, rather than composition on a 
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polished specimen surface (see ASTM E175 for standard terminology for microscopy). 

Inclusions are first classified into four types based on their shape (not their chemical 

composition despite the Type names): Type A – Sulfide Type, Type B – Alumina Type, 

Type C – Silicate Type, and Type D – Globular Oxide Type. Secondly, the inclusions are 

categorized as ‘thin’ or ‘heavy’ based on thickness or diameter. Thirdly, the inclusions 

are categorized by severity level which is based on the number or length of the particles 

present in a 0.50 mm x 0.50 mm field of view. ISO 4967 includes these same four types 

but also has a fifth group, Group DS – Single globular type, a circular particle with 

diameter greater than 13 μm.

A disadvantage of this process is that the measurement field size (0.5 mm x 0.5 

mm) is small so that many fields may need to be measured to accurately represent the 

specimen. Only the specimen area examined is represented by the rating since steel often 

differs in inclusion content not only from heat to heat, but from ingot to ingot in the same 

heat and in different portions of the same ingot. For wrought steel, the sampling should 

not be done larger than one heat. 

ASTM E1245 is similar to ASTM E45 but uses auto image analysis with a 

reflected light microscope or SEM and an auto image analyzer to measure basic 

characteristics of the morphology of inclusions in steel or other metals. Measurements 

include the number of sulfide and oxide inclusions per unit area, area of each inclusion 

type, and mean distance between inclusions. Inclusions are detected with grey level 

intensity (see ASTM E986 for beam size characterization).
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ASTM E2142 covers procedures to obtain particle size distribution, chemical 

classification, and ASTM E45 ratings of inclusions in steels using automated SEM with 

X-ray analysis and automatic image analysis. There are three methods described. Method 

1 is equivalent to ASTM E45 but the SEM characterizes morphology and is used to sort 

particles into classes. Method 2 is based on sorting inclusions by chemistry into 

traditional classes defined in ASTM E45. Method 3 defines procedures to analyze and 

report inclusions by arbitrary size distribution and chemical classification.

ASTM E2283 describes a standard practice to estimate the extreme value 

distribution of inclusions or second phase constituents in steels. Generally the largest 

oxide inclusions within the specimens are measured but the method can be used to 

measure other microstructural features. This practice is not suitable for assessing the 

exogenous inclusions in steels and other metals because of the unpredictable nature of the 

distribution of exogenous inclusions. This practice is based on using the specimens 

described in ASTM E45. 

6. Voids, microcracks and delaminations

The amount of porosity, voids, or pores within a microstructure, cracks or 

delaminations, possibly between build layers, is important to characterize for AM 

materials. Some AM materials need to be fully dense for high strength purposes, while 

other materials require surface porosity. Surface porosity and surface roughness are not 

covered in this report. 
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There are at least two general types of methods to evaluate a microstructure for 

porosity, cracks or delaminations: destructive and non-destructive evaluation (NDE). 

Destructive evaluation involves cutting a specimen from the main body of the material in 

order to view a representative sample. ASTM E3 and ISO 4505 describe selection, size, 

cutting, cleaning, mounting, grinding, and polishing of metallographic specimens for 

microstructure analysis using an optical microscope or SEM. Many of the standards 

mentioned already address characterizing features of interest from a cut specimen using 

either the optical microscope or SEM. ISO 4499-4 and ISO 4505 include reference 

photomicrographs with which to characterize porosity levels.

NDE involves determining material properties without causing damage to the 

material. Several factors are important when considering which NDE method to use for 

detection, for example, the material being examined, or what type of material properties 

are of interest. ASTM E543 has an appendix listing different NDE methods and the 

material properties measured. It is a standard useful for NDE testing on any material. It 

also includes typical flaws detected along with advantages and disadvantages of each 

technique. ASTM E543 serves as a good reference by including a list of ASTM standards 

related to each NDE method.

A few of the ‘typical discontinuities detected’ listed in ASTM E543 include 

voids, the absence of material or a separation not caused by loading or internal stress. 

Another discontinuity listed is cracks, the separation of the material in any direction 

usually due to external loading or internal stress. Delaminations, the separation between 

layers due to external loading or internal stress, are also listed as discontinuities in ASTM 

E543. 
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Another type of NDE method involves using fluorescent or visible penetrant and 

developer materials to visually observe the presence and location of discontinuities open 

to the surface of metallic materials. ASTM E165 is a good starting point for these 

methods and lists several ASTM standards describing fluorescent and visible penetrant 

processes for metals (E1208, E1209, E1210, E1219, E1220, E1418, E2297).

Sample preparation (cutting, polishing, etching)

Since the primary objective of examining microstructure metallography is to 

reveal constituents and structure of metals and their alloys by means of optical 

microscope or SEM, proper preparation is of major importance. ASTM E3 provides a 

guide for preparation of metallographic specimens. It recommends a specimen location 

based on the purpose of the study: for general studies or routine work specimens may be 

taken to reveal the maximum material variations or from the part ends; for the study of 

failures, specimens may be taken as close as possible to the fracture or initiation of 

failure; and for research studies, the nature of the study will dictate the specimen location. 

Once the specimen location is determined, the specimen orientation(s) is chosen: 

longitudinal, transverse, and/or parallel to the surface. Three recommendations are given 

to cut metallographic specimens, sawing, abrasive cut-off blade, or a shear, tools that 

minimize altering the sample structure. Suggestions for specimen size, cleanliness, 

mounting the specimens, and suggestions on manual and automated grinding and 

polishing are also described. ASTM B665 and ISO 4499-1 also describe metallographic 

preparation for cemented tungsten carbides or other hardmetals.
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Etching specimens for metallographic examination is important to highlight 

phases of interest. ASTM E407 contains tables of metals with etchants to highlight 

specific phases for microscopic evaluation. Also included are the etchant composition 

and procedure.

Inclusion ratings, done manually using ASTM E45 or automatically using ASTM 

E1245 are influenced by the quality of the specimen preparation. ASTM E768 provides 

examples of proven specimen prep methods that retain inclusions in polished steel 

specimens. It is also a guide to determine if the prepared specimens are of suitable quality 

for subsequent inclusion ratings. Two preparation methods are discussed for steel 

metallographic specimens that will be analyzed for nonmetallic inclusions with automatic 

image analysis (AIA) (Silicon Carbide Procedure and the Rigid Grinding Disk 

Procedure).

Conclusion and next steps

Most of the standards reviewed in this report address characterizing metal 

microstructural features that are not process specific. These standards therefore appear to 

be capable of addressing metals made by AM processes. There are some unique aspects 

of AM materials that may require attention when applying existing microstructural 

standards. One of these is that the additive manufactured layered build process, such as 

the layered process used in ‘laser-powder-bed-fusion’ (LPBF), may result in anisotropic 

material properties. The anisotropic nature will require that manufacturers take additional 

notes when preparing, sectioning, and during microstructural analysis such that specimen 
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direction is always reported and that microstructure analysis is done in different 

directions, e.g., parallel and perpendicular to the build direction (ASTM F2971, ASTM 

F3122, ISO/ASTM 52921). 

Another unique aspect of LPBF AM materials is their microstructure based on the 

AM process of solidifying powder layers to form a part. A result of this layered process 

can be weaker interfaces between layers leading to delamination. Since delamination is 

one of the major weaknesses of laminated composites, there are standards that address 

delamination and crack growth resistance for layered composite materials (D5528, 

D6115, D6671, E1922, ISO 15024, ISO 15114, ISO/DIS 19927). For metals however, 

standards exist for crack growth resistance (E399, E1820, E1304, ISO 12135) but not for 

the unique AM case where the metallic material has been formed in layers.

Microstructure analysis including preparation of metal samples is often a ‘trial 

and error’ process. Even minor structural differences can occur among metal samples 

taken from the same bulk metal section. Existing standards describe general methods or 

recipes to serve as a starting point to perform microstructure analyses. Metal specimens 

are prepared mostly based on reference books and past successful personal laboratory 

practice. The customized nature of this work is well known to metal microstructure 

experts, but not clear to the AM community trying to understand how to apply traditional 

techniques to AM metals. A ‘best practice’ report for using existing standards to 

characterize the microstructure of AM materials may be the next appropriate step. 

However, as microstructure analysis continues on AM metals, a need for a specific 

standard may arise. 
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As many of the existing standards involve manual or image analysis methods to 

make measurements, sample selection is important as noted in many standards (E3, E45, 

E562). A sample should be representative of the general microstructure, or representative 

of a general location within a lot, heat, or part. Care will be necessary that selected AM 

samples have a representative microstructure for analysis. Attention to the number of 

samples, their location, and direction is important to adequately represent a specimen just 

as it is required for non AM metals analysis. However, unlike traditional metal analysis, 

AM metal samples will not be categorized by heat or ingot. 

The above standards address how to assess microstructure or what to assess, 

however, ideas for future AM related standards include when or where to assess 

microstructure. A few ideas include:

• A standard recommending where along the z axis (height) to analyze, either 

destructively or non-destructively. For example, at different heights during the 

AM fabrication process, the microstructure may change depending on the height 

of the layers. Powder characteristics or laser intensity may also be affected by the 

height of the build.

• Defining where on an AM part to analyze in the x and y axes, either destructively 

or non-destructively, since powder or laser intensity characteristics may also 

change depending on these directions within an AM part.

• A standard recommending how frequently microstructure analysis should be 

assessed. Every AM part could have a complimenting microstructure specimen 
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fabricated next to the part for analysis, or a microstructure specimen could be 

analyzed after a specific number of AM parts are fabricated.

• A standard recommending a template for the AM part manufacturer/buyer listing 

possible expectations to be discussed to include how, when, where, and what 

microstructure assessments will be conducted and by whom. 

• A standard recommending how to present microstructure results consistently, and 

with enough pedigree to provide adequate records of the data.
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Automatic Image Analysis (ASTM International, West Conshohocken, PA).

ASTM International (2007) ASTM E1268-01 (Reapproved 2007) - Standard Practice for 

Assessing the Degree of Banding or Orientation of Microstructures (ASTM International, 

West Conshohocken, PA).

ASTM International (2014) ASTM E1304-97 (Reapproved 2014) - Standard Test Method 

for Plane-Strain (Chevron-Notch) Fracture Toughness of Metallic Materials (ASTM 

International, West Conshohocken, PA).

ASTM International (2010) ASTM E1382-97 (Reapproved 2010) - Standard Test 

Methods for Determining Average Grain Size Using Semiautomatic and Automatic Image 

Analysis (ASTM International, West Conshohocken, PA).

ASTM International (2010) ASTM E1418–10 - Standard Practice for Visible Penetrant 

Testing Using the Water-Washable Process (ASTM International, West Conshohocken, 

PA).

ASTM International (2015) ASTM E1820-15 - Standard Test Method for Measurement of 

Fracture Toughness (ASTM International, West Conshohocken, PA).
22

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ASTM International (2015) ASTM E1922-04 (Reapproved 2015) - Standard Test Method 

for Translaminar Fracture Toughness of Laminated and Pultruded Polymer Matrix 

Composite Materials (ASTM International, West Conshohocken, PA).

ASTM International (2008) ASTM E2142-08 - Standard Test Methods for Rating and 

Classifying Inclusions in Steel Using the Scanning Electron Microscope (ASTM 

International, West Conshohocken, PA).

ASTM International (2014) ASTM E2283-08 (Reapproved 2014) - Standard Practice for 

Extreme Value Analysis of Nonmetallic Inclusions in Steel and Other Microstructural 

Features (ASTM International, West Conshohocken, PA).

ASTM International (2015) ASTM E2297-15 - Standard Guide for Use of UV-A and 

Visible Light Sources and Meters used in the Liquid Penetrant and Magnetic Particle 

Methods (ASTM International, West Conshohocken, PA).

ASTM International (2013) ASTM E2627-13 - Standard Practice for Determining 

average grain size using electron backscatter diffraction (EBSD) in fully recrystallized 

polycrystalline materials (ASTM International, West Conshohocken, PA).

ASTM International (2013) ASTM F2971-13 - Standard Practice for Reporting Data for 

Test Specimens Prepared by Additive Manufacturing (ASTM International, West 

Conshohocken, PA).

ASTM International (2014) ASTM F3122-14 - Standard Guide for Evaluating 

Mechanical Properties of Metal Materials Made via Additive Manufacturing Processes

(ASTM International, West Conshohocken, PA).

International Organization for Standardization (2012) ISO 643:2012 - Steels —

Micrographic determination of the apparent grain size (International Organization for 

Standardization, Geneva, Switzerland).
23

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International Organization for Standardization (1990) ISO 2624:1990 - Copper and 

copper alloys — Estimation of average grain size (International Organization for 

Standardization, Geneva, Switzerland).

International Organization for Standardization (1978) ISO 4505:1978 - Hardmetals -

Metallographic determination of porosity and uncombined carbon (International 

Organization for Standardization, Geneva, Switzerland).

International Organization for Standardization (2008) ISO 4499-1:2008 - Hardmetals —

Metallographic determination of microstructure — Part 1: Photomicrographs and 

description (International Organization for Standardization, Geneva, Switzerland).

International Organization for Standardization (2008) ISO 4499-2:2008 - Hardmetals —

Metallographic determination of microstructure — Part 2: Measurement of WC grain 

size (International Organization for Standardization, Geneva, Switzerland).

International Organization for Standardization (2016) ISO 4499-4:2016 - Hardmetals —

Metallographic determination of microstructure — Part 4: Characterisation of porosity, 

carbon defects and eta-phase content (International Organization for Standardization, 

Geneva, Switzerland).

International Organization for Standardization (2013) ISO 4967:2013 - Steel —

Determination of content of nonmetallic inclusions — Micrographic method using 

standard diagrams (referenced in ASTM E45-13) (International Organization for 

Standardization, Geneva, Switzerland).

International Organization for Standardization (1988) ISO 9042:1988 - Steels — Manual 

point counting method for statistically estimating the volume fraction of a constituent 

with a point grid (International Organization for Standardization, Geneva, Switzerland).
24

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International Organization for Standardization (2002) ISO 12135:2002 - Metallic 

materials -- Unified method of test for the determination of quasistatic fracture toughness

(International Organization for Standardization, Geneva, Switzerland).

International Organization for Standardization (2000) ISO 14250:2000 - Steel —

Metallographic characterization of duplex grain size and distributions (International 

Organization for Standardization, Geneva, Switzerland).

International Organization for Standardization (2001) ISO 15024:2001 - Fibre-reinforced 

plastic composites — Determination of mode I interlaminar fracture toughness, GIC, for 

unidirectionally reinforced materials (International Organization for Standardization, 

Geneva, Switzerland).

International Organization for Standardization (2014) ISO 15114:2014 - Fibre-reinforced 

plastic composites — Determination of the mode II fracture resistance for 

unidirectionally reinforced materials using the calibrated end-loaded split (C-ELS) test 

and an effective crack length approach (International Organization for Standardization, 

Geneva, Switzerland).

International Organization for Standardization / ASTM International (2013) ISO/ASTM 

52921:2013(E) - Standard Terminology for Additive Manufacturing—Coordinate 

Systems and Test Methodologies (International Organization for Standardization, Geneva, 

Switzerland / ASTM International, West Conshohocken, PA).

International Organization for Standardization (2016) ISO/DIS 19927 - Fibre-reinforced 

plastic composites -- Determination of interlaminar strength and modulus by double 

beam shear test (under development) (International Organization for Standardization, 

Geneva, Switzerland).

Metals Handbook 9th Edition, Volume 9 Metallography and Microstructures, American 

Society for Metals, Metals Park, OH, 1985.
25

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Ruhle, M., Transmission Electron Microscopy, Metals Handbook Ninth Edition, Volume 

9 Metallography and Microstructures, American Society for Metals, Metals Park, OH, pp. 

103-122, 1985.