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My primary project is involved with understanding how temperature changes the response of grain boundaries to impinging dislocations. It is known that at room temperature, the slip system activated by a grain boundary in response to a dislocation pile-up is determined by competition between the local resolved shear stress, which is dictated by the pile-up stress field, and by the strain energy density of the grain boundary. However, increasing the temperature increases the mobility of grain boundary dislocations. The motion of these dislocations effectively smears the strain energy density along the grain boundary. It is unclear if this changes the factors controlling the selection of slip system activated by a grain boundary in response to a stress concentration. In order to more accurately study the grain boundary/dislocation interactions, I am currently working on methods to combine in situ straining experiments with electron tomography to achieve four dimensional characterization of the interactions.

I am also studying the thermal stability of nanograin Ni thin films. Annealing nanograin thin film nickel samples causes abnormal grain growth, resulting in a bimodal grain distribution. This abnormal grain growth is studied using pulse-laser deposited thin film nickel samples annealed in situ in the TEM. The grain growth is captured using a CCD camera for subsequent analysis with the objective being to investigate how the grain growth varies with varying conditions such as deposition energy and temperature.

Figure 1. Grain boundary/dislocation interaction in 304 stainless steel. Direction of dislocation motion is indicated by arrows.

Figure 2. Three dimensional model of interaction created from tilt series acquired at the area shown in Figure 1.

PhD in Materials Science and Engineering

BS in Physics and Mathematics, Brigham Young University (2008)

MS in Mechanical Engineering, Brigham Young University (2009)

In situ TEM studies of grain growth rate in nanograin PLD nickel

In situ TEM studies of dislocation-grain boundary interactions under strain at elevated temperatures