Materials Science

While working at the Army Research Lab, I have designed, had fabricated, and tested physical components using Solidworks 3D modelling. The most notable example is a new nozzle assembly, which I took from concept to final product installed in the machine, with multiple swappable nozzles to deposit lines of different thicknesses.

I worked in the Cordero Additive Lab at Rice University researching cracking during constrained sintering. Sintering is the process by which particles merge together by the application of heat or pressure without melting.

During this process, the density of the material increases, typically from around 30% density to 50-90%. If the piece being sintered is constrained or has a complex shape, this shrinkage can lead to cracking.

I designed samples and a frame to hold and constrain them in Solidworks, then 3D printed the the samples myself out of alumina on an ExOne binderjet printer. I then set up a camera focused into a tube furnace where the samples and frames were heated to 1000+ degrees Celcius, took pictures every few seconds, and compliled those pictures into a movie with ImageJ that could be analyzed to track crack formation over time, which you can see below.

This research was published as “In situ observations of cracking in constrained sintering” in the Journal of the American Ceramic Society, which gave it the “Best Paper of 2018” award.

In college, my capstone project was to design an alloy that was easy to weld, had a high yield strength (> 70ksi) and corrosion resistance (comparable to Inconel 625), and had less than 5% dilution from the substrate metal for use in CRA (corrosion-resistant alloy) cladding. CRA cladding of pipes is cheaper than a solid CRA pipe, and increases the pipe lifespan when transporting harsh materials.

My group chose to make a nickel-based alloy, due to the fact that nickel alloys are already in use for CRA cladding and are highly resistant to many forms of corrosion and high temperature oxidation. The strengthening mechanisms we chose to use were solid solution strengthening (introducing trace elements into the alloy to impede dislocation movement) and precipitation hardening (heat treatment).

We used two models to predict the yield strength of our alloys, a linear model derived from commercial nickel alloy composition and strength data, and the Feltham Tough solid-state physics model from scientific literature. From these models, we chose to test adding Niobium, Tungsten, Aluminum, and Lanthanum to our alloy.

A plasma-transferred arc welding machine was used to create our alloys out of premixed powders. I wrote low-level G-code to operate the welding machine, covering the surface of the steel substrate with our nickel alloy.

We performed microhardness tests (ASTM E92), tensile tests (ASTM E8), and pitting and corrosion tests (ASTM G48). This required extensive sample preperation, including grinding and polishing the surface, cutting out specimens, and mounting samples in acid.

In the end, our alloy, named 625M after Inconel 625 which it was based on, achieved most of the goals set for it. It had good weldability, high yield strength, and good corrosion reistance. The iron dilution ranged from 5-15%, which didn't meet our standard, but that could be solved with further research.