Thermo Scientific Precipitate Analysis User Manual
Precipitate Analysis in Metals with
the Automated Particle Workflow
Transmission electron microscope workflow for
unattended, high-throughput imaging and data
analysis of nanoscale precipitates in steel alloys.
Introduction
Metals researchers seek to improve the various mechanical
properties of materials, such as steels, in order to meet modern
industrial and manufacturing demands. In particular, precipitates
formed during steel manufacturing are known to have a
significant impact on the mechanical properties of the resulting
material. The exact nature of these precipitates continues
to be an active area of research, and transmission electron
microscopy (TEM) is the preferred tool for this analysis, as it is
capable of providing high-resolution nanoscale information on
the sample.
This routine analysis, however, requires large data sets in order
to obtain reliable, statistically significant results. The Thermo
Scientific
unique hardware and software into a robust, automated, and
unattended nanoparticle characterization workflow ideally suited
for precipitate analysis in steels.
™
Automated Particle Workflow (APW) combines our
NbTi
2 μm 2 μm
This STEM image shows the heterogeneous distribution of
precipitates on this microalloyed steel carbon replica sample.
EDS maps of the corresponding area show precipitates, including titanium
(yellow) and niobium (purple).
Particle size distribution of titanium niobium compounds
300
250
200
150
100
Number of particles
50
100 nm
Magnified area of the EDS map shows the compound of titanium
(yellow) and niobium (purple) and zones where they overlap (orange).
Goal
Microalloy, or high-strength low-alloy (HSLA), steels are common
in many industries, such as oil and gas extraction, construction,
and transportation. Due to small additions of vanadium, niobium,
and titanium, these steels have shown improved strength and
toughness compared to mild carbon steel. These microalloys
(<0.10% alloying elements) react with carbon and nitrogen to
form nanoscale carbonitride precipitates. After casting, Ti-Nb-V
carbonitrides are partially dissolved by reheating and then reprecipitated during rolling and subsequent thermomechanical
processing. The improved mechanical properties of HSLA steels
result from grain refinement during hot rolling, which is governed
by complex precipitates, and precipitation hardening.
While HSLA steels have been utilized for over 50 years, the
science behind how precipitates form is still an area of ongoing
research. Transmission electron microscopy can be used to
answer vital questions, such as:
• Which types of precipitates are better for pinning austenite
grain boundaries?
• What effect do compound precipitates have?
Additionally, recent second- and third-generation advanced
high-strength steels (AHSS) have been replacing some HSLA
steels due to their substantially higher strength and potential
for light-weighting. AHSS are a wholly new grade of steel with a
much higher amount of alloying (e.g., >1% aluminum and silicon
in third-generation AHSS), which in turn means that they include
new types and sizes of nanoscale precipitates.
0
50 100 150 200 250 300 350 400
Distribution of the overall particle length. Over 1,400 compound particles were
characterized. Total a nalysis time was one hour, inclu ding the overview images.
Length (nm)
Solution
Traditional TEM methods consist of manual spot analysis of the
precipitates’ chemical composition or separate particle imaging
without chemical information. Additionally, energy dispersive
spectroscopy (EDS) can be performed on the TEM in order to
determine the composition of individual precipitates, as it can be
heterogeneous across a sample. The problem is that this method
of analysis is time-consuming and tedious, and the TEM operator
can only collect compositional information for a few dozen
particles per day.
With APW, however, this entire process becomes automated
and can be left unattended, freeing the researcher’s time for
more critical tasks. Thousands of data points can be easily
collected and characterized in one day, and statistically
relevant data sets can, in some cases, be produced in just
one hour.
This accelerated analysis facilitates faster alloy and heat
treating process development by significantly reducing the
time spent on characterization.
Automated
Particle
Workflow
in action
Duration 2:49
Whether the grade of steel is old or new, the analysis of
precipitates is key to understanding the effectiveness of the
alloying and heat-treating processes. APW is specifically
designed to facilitate this kind of crucial characterization.
Find out more at thermofisher.com/APW
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are the property of Thermo F isher Scientific Inc. and its subsidiaries unless otherwise specified. AN 0167-EN-03-2021
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