Quantitative Microstructural Analysis

CALL FOR PARTICIPATION

Technical Work Area 37

Project 4
Measurement of dislocation density in metallic materials byTransmission Electron Microscope (TEM)

Objectives

Standardization Needs

Theaimof
thisinternational
interlaboratory comparison is to determine
the dislocation density in thin metals byusing Transmission Electron Microscope(TEM).

The TEM method to measure thedislocationisthemostdirect
measurement procedure, and its result
can be used as a reference for otherindirect methods. A good dislocation
image, which shall display as manyvisible dislocations as possible andhave a homogenous background, is thebasics of the intersections-counting
method and can greatly facilitate theautomation of the process of accurate
counting. There are many parameters,such as sample condition, imaging
method, etc., which will significantly
affect the quantitative analysis resultsof the dislocation density. The manual
counting of the dislocation intersections
is time-consuming and troublesome. An
automatedcounting
methodisrecommended and also specified in the
prepared measurement protocols inorder to obtain reproducible results. It
Based on the results gained in thisinterlaboratorycomparison,
thestandardized measurement of thedislocation density in metals by TEM
will be developed and included into theISO 13139 project.

The results will be used directly for further
development of the ISO/PWI 13139„Microbeam analysis - Analytical electron
microscopy - Measurement of thedislocation density in thin metals by TEM“
with a validated measurement procedure,
which will be optimised based on theresults gained in this interlaboratorycomparison.

BackgroundThe dislocation is the physical nature of
the deformation, and the dislocation
density in metals is closely related to theirstrength and toughness. The dislocation
density can be measured by TEM via anintersections-counting method, which cansolve the 3D measurement by a 2Dmodel.
Taking STEM images of a dislocation,
counting intersections of a grid on thedislocation image and determining thethickness of the foil are the three key
points of this method.

Relevant Standards
Committee
ISO/TC 202/SC 3 Analytical Electron
Microscopy

Intersections-counting on
the dislocation image

Determination of foil thickness by CBED methodWork Programme

FundingThe
dislocationdensity
ina
designated grain in the delivered foil
sample will be measured by S/TEM,
according to a protocol including thedislocation image acquisition and thefoil thickness determination.

Participants will fund their own
involvement (approx. 1 day work).

Sample will be prepared by the project
leadership and provided to eachparticipant.
The project is due to start in May 2024
for a duration of 9 months.

Deliverables andDissemination
This interlaboratory comparison will beusedtodevelopISO13139“Microbeam analysis - Analyticalelectron microscopy - Measurement ofthe dislocation density in thin metals”.

International Participation
Current participation includes China.
Additional participants are verywelcome.

For more information:
Project Leaders

Dr Yang MENGDr Xinhua JuShougang Group Research Institute ofTechnology, China

mengyang@shougang.com.cn
TWA Chair

Vasile-Dan Hodoroaba

Federal Institute for Materials Research andTesting (BAM), Germany

www.vamas.org
March 2024