As an applications specialist, I have encountered various problems over the years. There is always a common goal among EBSD users—to improve the EBSD indexing rate. Even a user who mainly tests relatively easy steel samples may run into deformed samples and intergranular precipitates that are difficult to calibrate, so they still need to improve the indexing rate. Ideally, we want to get a beautiful EBSD IPF map like Figure 1; however, the reality is that we often fail to get a map with such a high indexing rate.
Figure 1. IPF map with a very high indexing rate.
Recently, I received a phone call from a customer asking for help. She had tricky ceramic samples with low crystallinity and fine grains, which are hard to index. The indexing success rate was only 5.48% from the area she tried to analyze (Figure 2). She wanted to see if we could improve it.
Figure 2. Ceramic sample with an indexing success rate of 5.48%.
Of course, we can.
EDAX has a set of solutions to improve the indexing rate, as shown in Figure 3. If I had a direct detector like the Clarity EBSD Analysis System, I would obviously get better results. However, I only have a CMOS-based Velocity Super in my lab.
During the data collection process, users can optimize different parameters, such as background processing, or Hough parameters, to fit real-world samples. Combined with a unique hexagonal grid sampling and triplet indexing solution, EDAX gets a better indexing rate, which is very important for challenging samples.
If the data is not ideal, we can process the result using NPAR. With NPAR, it averages the patterns to improve the indexing rate of challenging samples considerably. Also, in OIM Analysis v8.0 or higher, a module is available that can perform background processing again on the saved patterns to improve the indexing rate further.
Figure 3. EDAX’s optimized EBSD solution.
I analyzed the sample and saved the patterns. Then I used OIM Analysis to post-process the patterns, as shown in Figure 4. The original pattern is quite fuzzy, and the bands were not clear. After NPAR processing, it improves the signal-to-noise ratio of the pattern, and the bands became clearer after further background processing.
Figure 4. (a) The raw pattern, (b)NPAR, (c) NPAR+dataset background, and (d) NPAR+dataset background+dynamic background.
Of course, the processed patterns have indexing success rates. Figure 5 shows the IPF map of the data after a series of post-processing steps were taken, as described in Figure 4. The indexing success rate improved to 24.1%.
Figure 5. An IPF map with an indexing success rate of 24.1%.
For this user’s case, the indexing success rate was greatly improved and was within an acceptable range. But to achieve our goal of improving the indexing rate of challenging samples, there is much more that needs to be done.
The above indexing success rates were achieved after CI >0.1 filtering. For those points with a CI <0.1 (the black areas in the IPF map), we can further process them. EDAX recently added OIM Matrix, which includes dictionary indexing as a supplementary solution. As we all know, the result of dictionary indexing is usually better. I would expect a higher indexing success rate on the customer sample if I could use dictionary indexing to process it further.
If we push the limit, we can use the Clarity Direct Electron System to test this sample. In fact, the super-sensitive, low-beam current requirement is ideal for testing this type of sample. Maybe we can expect a better result with Clarity?
Figure 6. Will the result improve with Clarity?
The goal of improving the indexing rate can be summed up in one sentence from a Chinese poem published in roughly 300 BC: The journey is long, but I will search up and down.
Dave Durham, Western Region Sales Manager, EDAX/Gatan
We are quickly approaching that special season where we are encouraged to momentarily put aside our busy schedules and take an inventory of the things in our lives that we may not have had a chance to appreciate throughout the year. Considering the pandemic we’ve all been experiencing during the majority of 2020, I think it is especially important to stay optimistic and find the positive things that have materialized during this challenging and weird year.
Professionally, as a salesperson for the company, I am undoubtedly very thankful for the fact that the team at EDAX has had the resolve to release several new and compelling products this year. Amazing! Even considering the challenges of 2020, there has been a steady stream of recent upgrades and technology that have allowed us to provide our customers with groundbreaking tools to make their work and research even more successful. All this during a period where, I would have thought, very little innovation would be introduced in the field.
First was the release of APEX 2.0 for Energy Dispersive Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD). This was a substantial upgrade to the APEX Software interface, integrating it with our EBSD product line, allowing our customers to analyze their sample’s compositional and structural characteristics, and implementing a handful of other critical improvements to the capabilities and functionality of the platform.
Figure 1. APEX Software user interface.
Then we announced the launch of the new Lambda WDS product line. These spectrometers utilize a proprietary X-ray optical module to give them much better sensitivity at low energies and extend the energy limit beyond 15 keV, giving them superior performance in compositional analysis within WDS applications.
Figure 2. Lambda WDS Analysis System.
We followed that up with another huge announcement – the release of our Clarity EBSD Analysis System. The Clarity is the world’s first commercially available direct detector of its type designed for EBSD, ideal for operating at low currents and low voltages, where typical phosphor-based EBSD technology is unable to collect usable EBSD patterns. This detector truly opens a new window into sample types and applications that have never been possible with EBSD analysis. Very impressive!
Figure 3. Clarity EBSD Analysis System.
Lastly, we released OIM Analysis v8.5, an improved version of our renowned post-processing analysis software for EBSD. This new revision added compatibility with APEX 2.0 and support for OIM Matrix, for dynamic pattern simulation and dictionary indexing, as well as a few significant upgrades to user functionality and ease-of-use.
Figure 4. Schematic of the dictionary indexing processes in OIM Matrix using a library of simulated patterns.
I want to give my sincere thanks to all the folks at EDAX who played a part in bringing each of these products to fruition in 2020. I appreciate the hard work you put in this year, in addition to the multiple years it takes to bring new products to market. I’m thankful that you’ve made my job easier as a salesperson, helping me keep customers excited and engaged with new products. And you’ve also played a significant part in advancing our customer’s research and productivity.
On a side note, I’d be remiss if I didn’t also say that I was thankful for the new sample preparation instruments, the Ilion II and PECS II, added to our product portfolio the AMETEK acquisition of Gatan this year. While the instruments themselves were not released in 2020, they are “new” to me, and I am very excited to introduce them to our customers moving forward. I believe they will allow the EBSD community to spend significantly less time preparing their samples for analysis while providing substantially better patterns than what they’re used to seeing through typical sample preparation techniques. We recently released an experiment brief on the subject.
Figure 5. (left) Gatan Ilion II System and (right) Gatan PECS II System.
Finally, I’m thankful for my health – I’ve lost about 15 pounds this year and feel like I’m in the best shape I’ve been in two decades. I’m also very thankful for my family, kids, and friends, whom I love and have loved me and supported me through all of 2020’s ups and downs. When I think of everything that has been going on in the world and how there are still so many good things going on in my life, considering all of the things that could have taken a turn for the worst, I’m thankful for that too. And all of that makes me enthusiastic and hopeful for a better year in 2021.
Collecting die-cast toy cars is a childhood hobby that I picked up again twelve years ago. As kids play with Hot Wheels in the United States, you are sure to remember Matchbox toy cars if you were a kid in the 1980s and 1990s in China, like me. The brand originated in the United Kingdom and was given its name because the original die-cast toy cars were sold in boxes similar to those in which matches came in. I stepped into this mini world at the age of four when my father bought me my first Matchbox toy car. During my adolescence, I enjoyed exploring my gradually growing collection. Many years later, when I was in graduate school, these toy cars captured my attention again while I was shopping for groceries. I ran into a small section with some Hot Wheels and Matchbox cars hanging on the pegs. I was so excited to see that my favorite childhood toy brand was still alive and immediately reconnected with my old hobby.
Besides collecting toy cars released in the current year, I started to search on the internet to re-collect the same un-opened models that became worn and even destroyed in my childhood. Soon, I expanded my collection to include toy cars made in the 1970s and even 1960s and started to collect detailed scale model cars that are about the same size. Although collecting Matchbox or Hot Wheels cars is a hobby that attracts a lot of adult fans around the world, these cars are toys that do not have small parts, and all the vehicle types are about three inches in length, regardless if it is a passenger car or a truck (Figure 1). On the other hand, matchbox-sized detailed model cars are classified as 1/64 the size of the actual automobile, with many small parts that are only suitable for ages fourteen and up. 1/64 scale models bring back memories in another way because I am collecting models of classic cars and trucks from the era in which I grew up. Figure 2 shows some impressive cars from my childhood and a fire engine from my neighborhood in Boston.
Figure 1. A vintage railway playset from 1979 that my daughter likes to play with, and some toy cars ranging from the 1970s to 2010s.
Figure 2. Some matchbox-sized detailed models (1/64 scale) of the cars and trucks that I grew up with.
Sometimes my five-year-old daughter rolls my toy cars on racetracks to figure out which one is the fastest. She also likes playing with my vintage railway playset. As a parent, my daughter’s interest made me a little concerned about lead paint since some of the toy cars she plays with were manufactured decades ago. For example, the railway playset dates back to 1979. Safety standards have been changed and revised over time, so I decided to figure out if these toys are lead-free. As an Applications Engineer at EDAX, I had more than one choice of material characterization technique. The Orbis Micro-XRF Analyzer can do non-destructive elemental analysis with the flexibility to work across a wide range of sample types and shapes, meaning I could put the toy cars directly into the analyzer to get the results. At that time, I was in the middle of testing new features in our new APEX 2.0 Software for EDS, so I decided to go with Energy Dispersive Spectroscopy (EDS) to give the new Batch Mode feature a try. With the benefits of EDS analysis and the Batch Mode feature in the APEX 2.0 Software, I was able to load all the paint samples into the SEM chamber and run them all at once using an Octane Elite Silicon Drift Detector. I scratched a tiny paint chip from each toy car and stuck it on a 25 mm adhesive carbon tab. Overall, I got 28 samples to analyze, ranging from the 1960s to the 2010s. They were mostly Matchbox, including the cars my daughter plays with, but some were also from other major toy car brands sold in the United States (Figure 3).
Figure 3. A 25 mm adhesive carbon tab with paint samples from my toy cars
The Batch Mode operation allows you to collect data sets at different stage positions as a batch operation. Since the paint samples were hand stuck on the tab, the distance between adjacent samples was relatively large, and a single field of view was only able to show one sample. The Batch Mode feature’s automated stage movement was extremely useful in covering the paint samples all over the carbon tab in one operation batch. I was able to store all the paint samples in a batch list, set up collection parameters (Figure 4), and click on the Collect button to wait for all the samples’ results. Fortunately, the results show that all the samples I analyzed do not contain lead. The identified characteristic peaks were correlated to the paint samples’ colors; titanium dioxide and zinc oxide were white, carbon was black, and sulfur-containing sodium silicate was blue (Figure 5).
Figure 4. The growing batch list of the paint samples.
Figure 5. Selected SEM images and spectra overlay of the paint samples. The arrow indicates that no Pb L peak (10.55 keV) is present.
On a side note, it was relatively easy to identify a single element from a bunch of spectra that the energy region around the lead peak was pretty clean without any overlapping peaks. I simply had to overlay all the spectra together and see if the lead peak stuck up from the background. If you need to identify multiple compounds of contaminants from various samples, examining every spectrum or doing quantification analysis and comparing how close these numbers are over and over again is very time-consuming. An easy solution is to use the Spectrum Matching feature provided by the APEX 2.0 Software. You can collect spectra from those contaminants to build a library for them first, and then you can run Spectrum Matching to compare the unknown samples to the library. If Spectrum Matching finds more than three matches for an unknown sample, it will display the top three matches with numerical values of fit% for each unknown sample. This feature provides a remarkable benefit in improving the efficiency of your experimental work.
Now, I can stop worrying about the toxic component and let my daughter play with the vintage toy cars as she likes. My only concern is that some are hard to find now, so be careful and don’t break my vintage toy cars!
Fred Ulmer, South East Regional Sales Manager, EDAX/Gatan
Roughly 10 years ago, I was introduced to the exciting world of research using Transmission Electron Microscope (TEM)/Scanning Electron Microscope (SEM) principles. Working first as a Gatan field service engineer, then service manager. It was my first crash course in these research principles. It was a lot to take in at the time, but the excitement and enthusiasm shown by a customer when they have their new piece of equipment installed and begin to generate data was such a payoff. It seems like every year that there is a new, exciting technique or technology to apply to user’s research that enables researchers to keep getting better data.
Recently AMETEK purchased Gatan, which allowed for a great partnership between already owned EDAX and newly acquired Gatan. Also, I switched to sales from service at this time, becoming the South East Sales Manager with Gatan, and shortly after, I became the EDAX South East Sales Manager. Again, a lot to take in at the time, but it was rest assuring that EDAX, like Gatan, is at the forefront of TEM/SEM research.
One of the most technological advances I witnessed was the introduction of the K2 & K3 direct detection cameras for TEM from Gatan. This technology has allowed users to achieve data that was previously unheard of. From cryo-techniques to direct detection Electron Energy Loss Spectroscopy (EELS), these systems have become a game-changer.
Figure 1. Breakthrough K3 result: 2.7 Å structure of the 20S Proteasome with the K3 camera and Elsa cryo-holder on a TF20. Data courtesy of Alexander Myasnikov, Michael Braunfeld, Yifan Cheng, and David Agard.
Unsure of how, or even if direct detection could be used in the SEM world, it was exciting to get word from EDAX that they were releasing a direct detection EBSD analysis system called the Clarity. This system is the world’s first EBSD detector based on direct detection technology. Current EBSD non-direct detection detectors have some drawbacks that include grain size and film thickness, causing localized blooming and some imaging artifacts in the EBSD patterns. So how does the Clarity overcome these drawbacks? It comes from the inherent design and technology of the detector. The Clarity does not require a phosphor screen or light transfer system. The technology uses a CMOS detector coupled to a silicon sensor. The incident electrons generate several electron-hole pairs within the silicon upon impact, and a bias voltage moves the charge toward the underlying CMOS detector, where it counts each event. This method is so sensitive that it can detect individual electrons. Coupled with zero read noise, the Clarity provides unprecedented performance for EBSD pattern collection. It can successfully detect and analyze patterns comprised of less than 10 electrons per pixel.
Figure 2. High-quality EBSD patterns collected with Clarity from a) silicon, b) olivine, and c) quartz.
Figure 3. Intensity profile across (113) band from the Hikari Super (blue) and Clarity (red) detectors showing improved contrast and sharpness with direct detection.
Direct detection will benefit many research areas like in‐situ microscopy, EBSD, 4D STEM, imaging beam sensitive materials, quantitative measurement of radiation damage, or quantitative electron microscopy. I am excited to see how the new generation of direct detection, like the EDAX Clarity, will continue to revolutionize the field of electron microscopy. Direct detection and electron counting are poised to advance electron microscopy into a new era. Let’s go direct detect!
I firmly believe that one of the factors that has helped EBSD advance as a microanalytical technique is that it makes beautiful pictures. Of course, these images are packed with valuable information regarding the microstructure of materials. But in addition to this scientific content, they catch your eye. In our lab, we have taken advantage of this by hanging the covers of different journals and publications that feature EBSD images collected with EDAX equipment (Figure 1). Some of these are images we have collected internally, and others are from our customers. It is a fun reminder of interesting work that has been done over the years.
Figure 1. Our EBSD cover collection.
We have had an exciting past 18 months with the EBSD product line at EDAX. We launched our Velocity high-speed CMOS camera, which delivers greater than 4,500 indexed points per second. We released the APEX Software for EBSD, our new data collection platform with powerful analytical capability coupled with an easy-to-use interface. We introduced our groundbreaking Clarity EBSD Analysis System, which is the first commercial direct detection system designed for EBSD. As part of the development, testing, and marketing of these new products, I have used these products to collect thousands of images, some of which are utilized to highlight the performance of these new tools.
So how do you choose what makes a good EBSD image? The first step is often picking an interesting sample, but interesting is in the eye of the beholder. Some examples are selected because they use specific materials, like aluminum, magnesium, or steel. I like samples that have interesting microstructures. Sometimes, this is from a novel processing approach, like friction stir welding or equal channel angular processing. Sometimes, it is from a multi-phase microstructure, where structure and chemistry can be characterized simultaneously with EDS-EBSD. Sometimes, it is application focused. In this example, I have selected a sample because it is an additively manufactured nickel alloy. Additive manufacturing is a market with growing interest, and the microstructure is important because it influences the final properties of the material.
Figure 2 shows an Inverse Pole Figure (IPF) map of this material, collected with the Velocity Super at >4,500 indexed points per second. This IPF map is colored relative to the surface normal direction, and I have included a (001) pole figure to show the crystallographic texture and a colored IPF key to help decipher the relationship between the colors and the crystal orientations, which is good practice. This image is interesting because it shows a (001) fiber texture, which explains why many of the grains are shaded red. This helps researchers understand how these grains were growing during the additive manufacturing process. But is it visually appealing? That’s a question I often ask as I share these images for different possible uses.
Figure 2. IPF Map of an additively manufactured nickel alloy collected with the Velocity Super at >4,500 indexed points per second.
One possible approach to improving the visual appeal of this map is to superimpose it with a grayscale image derived from other EBSD measurement metrics. Figure 3 shows the same IPF map combined with an Image Quality (IQ) map and a PRIAS (center) map. The IQ value is derived from measuring the brightness and sharpness of the diffraction bands within the EBSD patterns. The PRIAS map is calculated from the intensity of the signal onto an ROI positioned within the center of the EBSD detector. Both signals show microstructural contrast and add supplemental information to the IPF map.
Figure 3. IPF map combined with Image Quality (left) and PRIAS center (right) contrasts.
How about the colors, though? Is it too red? I hear that sometimes, but I wonder if it is because of the rivalry between the University of Utah (red – where I went to school) and Brigham Young University (blue – where some of my co-workers went to school). What can I do about this? One approach is to specify the IPF map relative to a different direction than the surface normal direction. Figure 4 shows an IPF map where I have selected a  sample vector. While it is harder to relate this to the fundamental additive manufacturing process, it does show how you are not limited to specific sample directions. This can be useful if, for example, the thermal gradient present during processing it not aligned with the sample normal direction. In this case, it gives us a different color distribution representing the same microstructure. Is this better?
Figure 4. IPF map relative to the  sample direction.
I have been looking at these maps for 25+ years now, so sometimes it is the new and novel that catches my eye. Figure 5 shows the same microstructure colored using a Quaternion Misorientation scheme. Here a reference orientation is used as a baseline, and the misorientation from this reference is used for coloring. Our OIM Analysis software has a wide range of different methods for visualizing microstructures. I personally really like the way this one looks. It is as much art as science.
Figure 5. IPF map with Quaternion Misorientation coloring.
When images meet those aesthetic criteria, they can be used for marketing, publications, covers, and even clothing. Figure 6 shows a scarf printed using an IPF from a skutterudite material. The crystallization of this material looks a bit like exploding fireworks. I have heard plenty of times that we should be in the tie or T-shirt business with the array of stunning images we can produce. I am always amazed that beyond visual appearance, the information on orientation, grain size and shape, deformation, and phase, among other things, that can be easily represented with EBSD. I hope to continue to find interesting examples to share with you. Special thanks to Tara Nylese for sharing the photo.
The seasons are changing here in the mountains of Utah. Autumn is at least one of my four favorites! I have made my home here, largely because of the drastic seasonal changes in climate and the ability to participate in gravity fed activities, like skiing and mountain biking. My personal life has become a game of maximizing my time in the mountains within the confines of what the weather and other commitments allow. Do I ride my bike at 5,000 feet elevation or 9,000 feet elevation? Do I pull out the skis or the fat tire bike for riding on the snow? Do I have to ride early in the morning when the ground is frozen to avoid the mud? Maybe I just escape to the desert for a weekend. No matter what the weather decides to throw at me, I have an answer. If I ever get bored, then mother nature will change things up for me soon enough. I have learned to adapt and enjoy the constant change.
Figure 1. A perfect autumn day on the trail.
Figure 2. Escaping to the desert. Maybe I will see Dr. Stuart Wright there.
Figure 3. Not enough powder for skiing? No problem.
Recently in my professional life, I have had to apply some of the same attitudes toward change. After spending my entire career with TSL, then EDAX, then AMETEK; I decided to leave and work for Gatan about five years ago. I was just shy of my 20-year anniversary with EDAX. It was a nice change of pace and scenery. I really enjoyed learning new products and getting in touch with cutting edge Transmission Electron Microscope (TEM) research applications that Gatan is involved with. Then the climate changed and AMETEK acquired Gatan! Things had come full circle, just like the seasons. Fortunately for me, selling EDS and EBSD is like riding a bike (pun intended)! I now get to associate with some old friends again and sell both Gatan and EDAX products. I’m trying to convince myself that there are never too many products to sell, just like you can never have too much snow. However, sometimes I wish there was more time in the day.
Figure 4. It’s impossible to have too much snow!
I am looking forward to the constant change that will come with the combined power of EDAX and Gatan products. Can we offer Gatan sample preparation equipment to EDAX Scanning Electron Microscope (SEM) users? We sure can! Check out the latest EDAX Insight newsletter to see an example. Can we offer heating stages to EDAX SEM users? Absolutely! Can we leverage the power of Electron Energy Loss Spectroscopy (EELS) and Energy Dispersive Spectroscopy (EDS) together with diffraction for the ultimate microanalysis experience for TEM users? I hope so! It will take some work, but like climbing mountains, it will be so worth it!
Figure 5. You can’t enjoy the descent without the hard work of climbing.
I am looking forward to being able to offer my customers more solutions to their research problems. No matter which way the wind blows; I expect to have the answer in the form of the combined EDAX and Gatan product portfolio. What research problems are you trying to solve? Let’s see what we can do together. See you out there!
I dare say that in everyday life, most people do not think about crystallography very often. Equally, when we think of grains, a familiar image that comes to mind is children playing on the beach, building sandcastles (or in good Dutch tradition, perhaps a dam to keep the sea out).
Children already know about building things. They know you must use moist sand to make nice figurines. They also know that when you dig too deep on the beach, that water may come in and wreck your castle. You have to know your stuff when you start building things. Parents stimulate these construction experiments by supplying the building materials for some serious out-of-the-box thinking. The children start small, developing new, and intriguing concept cars (Figure 1), and then move on to bigger ideas and perhaps they build robots (Figure 2).
Figure1. A concept car made of Duplo blocks.
Figure 2. Robots made from carton boxes.
Why should this stop when you grow up? Some people might say there is a screw loose inside if you occupy yourself with carton robots (I designed the robots for a children’s vacation camp ). Still, the fascination with building beautiful things remains at all ages. A while ago, my neighbor asked me to take a look at this impressive tower built of Anker stones without using any glue (Figure 3, https://anchor-stone.eurosourcellc.com/).
Figure 3. An Anker stone model of the Grunewaldturm in Berlin.
Engineers have never outgrown the desire to put bits together to build things, and with the knowledge they gained during their education and experience, amazing things have been created. But as with the Anker tower, to have a stable structure, you need to keep paying attention to detail. If you have ever built anything yourself, you know how important it is to use the right components and ensure that all the parts fit together.
During my work at EDAX, I often work with engineers who are creating and testing new materials. Such materials are typically being deliberately developed for certain purposes by mixing components and then treating them just so, but sometimes also found by accident. And of course, it is not only the composition of a material that defines its properties, it is also the microstructure that makes a material suitable for specific applications. When you take care to pick the proper starting material for your product, you can successfully build something. However, sometimes corners are cut, and things go wrong.
For example, take a look at the two montage EBSD maps of iron screws in Figure 4.
Figure 4. An EBSD IPF (Y) on image quality maps of a) a coarse grained screw and b) a fine-grained screw. All the green grains are aligned with one of the edges of the unit-cell cube facing towards the tip of the screw.
These are two multi-million-point EBSD maps showing the microstructure in two screws. The greenish color indicates that in both screws the crystallographic  direction lies along the length of the screw. This is indicative of the production process of the metal rods from which the screws are cut. The different purple colors in the head are caused by the stamp that shapes it and pushes the cross into the top of the screw. But that is where the similarities end.
The top screw shows a very coarse grain structure, while the bottom screw has a much finer interconnected grain structure. This difference in grain structure has consequences. When we zoom in on the shaft of the coarse-grained screw (Figure 5a), the large grains appear flattened in between the threads, and there is a strong change in grain size from the center to the edge of the shaft. In between the threads, some of these larger grains have even been forced apart to form cracks. This combination is bad news for the strength of the screw. When you tighten this screw, the force gets “focused” on the weak areas between the threads, and the screw breaks easily. In the fine-grained screw (Figure 5b), a minor grain size reduction is visible right at the edge of the shaft, but the internal structure is constant over the entire screw. This homogeneous structure distributes the force evenly over the screw, and it does not break easily.
Figure 5. Grain maps of the two screws shown at the same scale illustrating the difference in grain size. a) Shows a coarse-grained microstructure and b) depicts a fine-grained microstructure.
A final detail scan of the grain structure shows an additional difference (Figure 6). In the coarse-grained screw, long trails of carbide particles can be observed in between the grains, which effectively separate the grains and facilitate cracking. In the fine-grained screw, the grains show a lamellar martensitic microstructure with very few carbides. These microstructures exacerbate the difference in strength between the screws.
Figure 6. Detail maps of the grain structure in a) the weak and b) the strong screw.
The investigation example shown above was born out of frustration when I tried to build something, and the screws just kept breaking while I thought I was doing nothing wrong. So, I decided to cut up one of the failing screws and compare it with a screw from another box that had never given me trouble.
This was just about a screw used in a DIY project to put a wooden panel to a wall. Nothing crucial, you would think. But just imagine when this screw would have been used to hold up something a bit more impressive, like that big, heavy chandelier 10 meters above your head in the lobby of a hotel? Then suddenly, the microstructure of a humble construction component, such as a screw, becomes crucial, and thinking about the crystallography and grain structure of everyday items turns out to be really important.
As I prepared for some analytical work yesterday, I had to repolish a standard block. This made me think about how important these little blocks are and how often they are not cared for properly. With that in mind, I thought it might be useful to pass on some little nuggets of information I have gathered over the years from many sources.
The most important thing about caring for a block is knowing what is in it. Standard blocks can be purchased as a whole or personally made. No matter what, you need to know what you have! To do so, you should keep several copies of the following for every standard you have:
Optical light images of the whole block
SEM Montage image of the whole block (BSE and SE)
Individual image of each standard material
Composition of each standard material with sources
Notes on each standard
Figure 1. Each of our standard blocks has a name and a duplicate document. This packet has optical, BSE, and SE images of the standard. This allows us to quickly find the standard we want while having all the information easily accessible in hand.
Each of these above items is important. You want to keep both a visual record of your standards, a record of what it is and the condition that it is in, to allow you to track any issues that may pop up (Figure 1). Therefore, having a note section is important. You may find that one of the areas of your standard gives anomalous values and should be avoided. You want to make sure this information is easily accessible to everyone that uses the standard. I suggest scanning and keeping electronic copies in a shared folder on your desktop.
Besides the documentation aspect of care, physical care is just as critical. Most commercial standard blocks come pre-polished and carbon-coated. Over time, both of those will degrade and need to be redone. Usually, the carbon coating damages first, but you also need to check for burn marks and other beam damage done to the standard material itself. When repolishing and recoating, I usually do a solid 10 minute repolish with diamond paste. This removes enough material to eliminate the carbon coating and get new clean, undamaged surfaces while not change the physical appearance all that much. I try my best to avoid using an Al-based polishing material, as they tend to stick around too much and can interfere with my analysis on elements I use. With carbon-based polishing material, it is much easier to see the effects of the carbon. In the end, I do not tend to do quant work on carbon that much, while I often try to quantify aluminum. Whatever you do, document what was done. It can help you both head off and understand issues that may present.
While physically handling your sample, it shouldn’t need to be said, but you should never be touching your sample with ungloved hands. Your oils are bad for both the SEM cleanliness and the sample cleanliness. Avoid any sort of colloidal products with standards, as they do tend to flake with age. When not in use, samples should be held in a desiccator with good desiccant (Figure 3).
Figure 3. A good desiccator should have a rubber molding to help it hold a seal at a minimum. You should try to keep it under vacuum for the best results. While taking this picture, I noticed I should dry my desiccant or replace it. I have seen some users keep a small plastic bag of fresh desiccant in the desiccator as a quick visual reference.
There are many other tips I can think of sharing, but to wrap it up, standards are valuable in our industry. A good, well cared for standard will last multiple careers while giving consistent results time after time. Take the time to keep your standards in the best condition, and they will repay your time spent on them tenfold.
Dr. Jordan Moering, U.S. Eastern Sales Manager, EDAX
It was an icy morning in early November where I found myself, freezing, staring at a chunk of mangled aluminum, carbon fiber, and hickory nestled against mounds of pumpkins in a largely empty cornfield in Sussex County, Delaware. As the sun began to rise over the frosty ground, the carnal wreckage was investigated, pondered over, poked and prodded, touched, and engaged in any other means of characterization at the disposal of the rag-tag cohort of farmers, engineers, enthusiasts, and politicians surrounding me. In hindsight, this scenario seems like something out of a science fiction novel or perhaps a post-apocalyptic memoir, but I can assure you that this is a common sight to behold. Common, at least, at the World Championship Punkin Chunkin.
As it turns out, the twisted composite beam was one of the first instances I experienced in witnessing true engineering failure firsthand. Although the beam failed in some of our early testing, it had previously been attached to a world-class, 7-ton, torsion catapult capable of launching pumpkins over a kilometer at nearly the speed of sound. It could withstand tensile loads exceeding the weight of a Boeing 747 and extended nearly 20 feet in length. All of that impressive performance was a thing of the past as I closely examined the jagged features at the fracture surface, the twists along the flanges of the I-beam, and the shards of carbon fiber shattered amongst the corn husks.
Figure 1. Replacing the broken “Throwing Arm” with a convenient spare that we had brought with us.
Although I was just a student at the time, I already recognized the characteristic ductile fracture surface before me. I might have squinted my eyes and imagined some fatigue striations within the metal surface, but sadly this was the only means at my disposal of diagnosing the problem at the time. In a laboratory setting, I would have been able to not only characterize the elemental composition of the beam (it was a gift from a benevolent team sponsor) but also fully describe the crystalline structure with techniques like EBSD, XRD, and EDS. This type of material identification study is routine with modern analytical instruments, but recent advancements have taken this a step further. Had I known then what I know now, the unprecedented capabilities of high-resolution EBSD and ultra-high sensitivity of direct detection could have allowed me to understand and quantify, quite literally, the stressed state of the surrounding metal at the fracture surface.
Figure 2. The most frequently used deconstruction and characterization device we had at our disposal – an angle grinder.
While my first foire into failure analysis lacked the sophistication of modern analytical capabilities, it did spark an intense curiosity into this critical line of work. The modern electron microscopist, lab technician, or researcher has a wealth of opportunity at his/her disposal for understanding how materials fail. Sometimes these failures originate at some inclusion or material defect that could have previously been detected by methods like micro-XRF or EDS elemental analysis. Other times, inherent weaknesses in the system concentrate stress in ways that might not be apparent to the naked eye. Techniques like high-resolution EBSD and X-ray diffraction might be used to prevent these calamities. The list goes on and on.
I’ve only been working at EDAX for several months now, but every day I wake up and get to work with individuals who face scenarios, not unlike my previous encounter with twisted beams and flying pumpkins. Although a researcher at semiconductor foundry might not be surrounded by farmers in the middle of a cornfield, they certainly may find themselves staring at an improperly functioning device, wondering where things went wrong. In this capacity and many others, I find myself relating to our customers. I empathize with their challenges, and I am excited to help them uncover solutions to some problems that they previously were not aware of.
Because if there is one thing I have learned from Punkin Chunkin and Advanced EM Characterization, it is that you never know what you will find under the surface of your material.