Just for you, Mom

My mom has been pestering encouraging me to write a post about my thesis topic for months. Here goes. My apologies in advance for any boredom you may experience.

My major (is it still called a major in graduate school? Shouldn’t I know this by now?) is material science engineering. Don’t feel bad if you’re still clueless; nobody else knows what it is either. (Also, materials engineers don’t know how to use semicolons, so don’t be angry if that was wrong.) The way that I describe materials science engineering is as follows:

Everything in the world is made out of some material. I’m the one who chooses the material to make it out of or makes the material stronger, lighter, more conductive, less conductive… and just generally more awesome. This involves a lot of thinking about how atoms stick together (structure), how that structure behaves under various conditions (properties), and how to improve the properties by changing the structure through clever manufacturing (processing). It’s fascinating and complicated and I love it.

My specific project for my Masters thesis involved a particular subclass of materials called metallic glasses. Conventional metals (You may be familiar with metals. Cars used to be made out of them.) have all their atoms arranged in a regular, periodic order (called the crystal structure) like in this picture of aluminum. Metallic glasses are special materials where the metal atoms are not arranged in any long range order. They look like metals, but their properties are very different. (For a really cool demo, check this out.)

The research group that I belong to investigates the mechanical properties of materials. Basically, we break things to find out how strong/tough/stretchy/durable they are.

My project has two parts. When metallic glasses break, their fracture surfaces show evidence of locally viscous flow. This has been compared to grease between two solid plates. I did some model experiments with a grease between solid substrates and looked at the morphologies which appeared to try to physically model what happens in metallic glasses in a more controlled environment. I varied the stress state, substrate shape, thickness of the viscous layer, and viscosity of the layer (through changing temperature and greases) and made some general conclusions about the appearance of a viscous fluid fracture surface based on those experiments.

The second part of my thesis deals with the mechanical behavior of a particular metallic glass made mostly of magnesium. I did tensile tests, bend tests, and hardness tests at various temperatures, experiments (X-ray diffraction) to determine whether the atomic structure was still amorphous (disordered) or it had crystallized, and differential scanning calorimetry to track the changes in structure with temperature.

I wrapped it up with a comparison of some metallic glass fracture surfaces from my research and from literature to the viscous fracture surfaces I’d seen in the model grease experiments. My conclusion was that there is some correlation between what is seen in the grease experiments and in metallic glasses, although there are a lot of things we still don’t know.

If anyone’s more interested, my whole thesis is available for your enjoyment at this link. I think it should be available for public download.

Otherwise, I’m ordering bound copies on Monday for a price anywhere between $25 and $60 per copy, depending on which website I look at and whether or not I have to put the title on the spine and whether I need to include signature sheets and whether or not I need to have a pocket in the back for a CD… Guess what I’m trying to sort out today?


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