Matt Nowell, EBSD Product Manager, EDAX
For better or worse, I am a golfer. The story of how I became a golfer helps explain my love for EBSD, and evolution as a material scientist. While I was at the University of Utah trying to decide on a major, I enjoyed fishing. Here in Utah, we have lovely access to many rivers, streams, and lakes with great fishing potential. When I started investigating Materials Science and Engineering as a degree, I thought it would be interesting to learn about the graphite used in fishing rods, and how the different processes used improved the performance of the rods. With this interest, I enrolled in the Materials Science department. Fortunately (for the fish I like to think), two things happened that changed my recreational and professional focus.
First, I enrolled in Organic Chemistry. Memorizing different molecules was not something that I excelled at. This dampened my enthusiasm for all things polymer-based, like composite fishing rods. Second, I was hired to work in the Electron Microscopy lab for the Materials Science department. This gave me lots of direct exposure to SEM, TEM, EDS, and even XRD instruments. It also helped to build a strong appreciation for sample preparation, but that’s the topic for another blog. All these things pushed me in the direction of materials characterization, and when I graduated, it led me to TSL, EDAX, and EBSD.
How does all this relate to golf? Soon after I started working, I played a round of golf with some friends. I had played a few casual rounds over the years, but nothing serious. Looking back, I consider myself lucky because the parking lot for the EM characterization facility was also the parking lot for the University golf course, and if I had been bitten by the golf bug at that point, things might have occurred differently. After this round, which I greatly enjoyed, I went to the local golf store thinking about different golf clubs. I found a set where the shafts of the club were manufactured by the same company that made my favorite fishing rod. This seemed like a sign to me, so I bought the clubs and jumped right into becoming a golfer.
It was great timing. EBSD scans were slow. To collect a 20,000-point scan, which was our typical target at the time, took 5-6 hours. It was easy to fit in 9 holes during some of these scans. Today, with our new Velocity
This tournament also allowed us to indulge and combine golf with work a little bit. The first trophy was constructed from an old port cover we no longer needed. The second trophy was of course a crystal trophy. As you might imagine, there was some discussion over what crystal structure would be most appropriate.
There is plenty of time to think during a round of golf, and one of the things I’ve thought about is how the club heads are produced. When thinking about this, we are considering either woods (or more accurately metal woods) or irons. Irons are typically either cast or forged. Forged clubs are generally positioned for the better players, but what caught my eye is that some manufacturers started marketing the idea of microstructure and the role of grains in the material. One brand even pushes what they call Grain Flow Forged.
Of course, just like the fishing rods, the processing of the club affects the properties. The key link is that the processing changes the microstructure, and the microstructure defines the properties. With that in mind, it’s a fun experiment to compare the microstructure of cast clubs versus forged clubs. Stuart Wright and I first did this experiment about 20 years ago for a conference on Materials in Sports, but given the increases in capability, it would be fun to reevaluate.
I sectioned and prepared EBSD samples from both forged and cast irons. These were both made with an unknown steel alloy and prepared with my standard metallographic preparation approach. Enough coarse-grained polishing was used to remove plating from the club surface. The resulting Image Quality + Orientation Maps (IPF relative to the surface normal direction) are shown below. These were collected from the face of the golf club. I prepared cross-sections for further analysis. I was a little surprised by both microstructures. The cast iron had a dual-component microstructure, with both generally equiaxed grains and needle shaped grain constituents. It looks a lot like a dual phase Ferrite-Martensite microstructure, but with martensite being tricky to directly identify with EBSD relative to ferrite, I indexed both regions with a BCC Ferrite material file. The local misorientations were higher in the needle shaped regions, and there were also some austenitic grains present in these regions. The forged iron microstructure has a bimodal grain size distribution, with larger equiaxed grains decorated and intermixed with smaller equiaxed grains. A second scan was collected at higher magnification and with a finer step size to better resolve these fine grains.
As expected, the microstructures of the forged and cast clubs are different. As a Materials Scientist and EBSD guy, I tend to think forging is a more interesting materials processing option. In this case though, both casting and forging have produced interesting microstructures that could use further investigation. I once bought a set of forged clubs, and it was with this set I made my only hole-in-one. I’m pretty sure there is a direct correlation, and when I buy my next set, I’ll continue my experimentations.