Evaluation of varying concentrations in metal matrix composites

Last Wednesday, students and faculty members meet in Hill Hall for a seminar hosted by a former student. Jacob Neuchterlein graduated from Mines last year and is currently working on his doctorate. His lecture, titled “Metal Matrix Composites developed through Self Propagating High Temperature Synthesis,” explained the process and need for condensing the size of particles “without changing the density of the product that much.”

The goal of changing the particle’s size is to create a metal that is stronger. With a smaller size, the yield strength and the ultimate strength of the materials increase. Neuchterlein explained, “These net-shaped parts are what the Military is interested in… they need high wear resistance and low weight.”

The primary compound discussed was Titanium Carbide (TiC). The methodology for Neuchterlein was to first have a chemical reaction to obtain TiC. This can be done in several different reactions, thus creating different products. “These products have different properties, different strengths, different reasons why we want them,” said Neuchterlein. The emphasized experiment involved the mixing of Aluminum with a Titanium Oxide and a Carbon Oxide. The end result would be an Aluminum Oxide and Titanium Carbide.
After placing the products in a mix, he chilled and pressurized the compounds. During the ‘cool pressing’ process, the molecules would compress in both volume of separation and volume contained by the compound. According to Neuchterlein, a smaller particle can be made by cooler temperatures by decreasing the adiabatic temperature because it is a “quenching of the reaction.”

At this point in the experiment, the pressed mix is a solid and is ignited. Neuchterlein explained that Gleeble’s Experiment is first used to yield information on the ignition temperature due to simultaneous ignition. The ignition is done by placing an electric current through a coil that the solid is placed on.

After the ignition, combustion takes place. Data is then collected for analysis of the purity of the compound. Neuchterlein then explained that the hardness and compression strength depend on the percent of TiC that is in the mixture.

With an increase of TiC in the mixture, the hardness and compression strength increases as well. Neuchterlein explains that this is what is wanted, as a material can increase strength without altering its mass.

The key points for Neuchterlein’s method were the melting and the die casting. In the melting, Neuchterlein added from 10% to 60% TiC in a Aluminum matrix. In the die casting phase, it was emphasized that this process is essentially pouring and pressing. The liquid mix would be put into a mold that would be pressed to allow for any pockets of inconsistencies and it also allows for a final compression of the compound to decrease in size.

Neuchterlein calmly answered the handful of questions and was on his way to converting members of the audience to a different methodology for this process of creating TiC.

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