WE Student Seminar: Emily Flitcraft & Samuel Luther

Emily Flitcraft

Graduate Student, Welding Engineering, OSU, advised by Dr. Carolin Fink

Optimization of rapid solidification techniques for Heusler alloy Ni2MnGa

Abstract

Ferromagnetic shape memory alloys (MSMAs) have the ability to revert back to original shapes and properties after significant deformation. When in single crystalline form, these alloys produce up to 10% reversible magnetic field induced strain (MFIS) which can be beneficial in actuators, sensors, and space applications. With the aim to utilize advanced manufacturing techniques for production, concern is risen for how Heusler alloy functional properties (i.e. MFIS) are affected by this multifaceted fabrication. Thus, there is a critical need to establish a fundamental understanding of how non-equilibrium processing (rapid solidification) and complex thermal cycling (reheating) affect microstructural evolution and functional properties. In partnership with the University of Pittsburg, the overall goal is to identify the fundamental mechanisms of processing-microstructure-property relations over several length scales that enable laser based advanced manufacturing techniques for functional Ni-based Heusler alloys. Research specifically focuses on Ni2MnGa Heusler alloy, processed with laser metal deposition. In order to create a processing-microstructure-property map for this material, the setup and optimization of various rapid solidification techniques was conducted. The different approaches that were studied to achieve very high solidification rates include a) levitation-drop melting, b) electrode arc melting, and c) laser beam melting. Determination of cooling rates for the different melting techniques was done using thermocouple and pyrometer measurements, IR camera, thermal modeling, and measurements of dendrite arm spacing on solidified samples. Initial characterization of rapidly solidified Ni-Mn-Ga alloy was performed using scanning electron microscopy (SEM), electron dispersive spectroscopy (SEM-EDS), and X-ray diffraction.

Bio

Emily Flitcraft graduated in December 2018 with a B.S. degree in Welding Engineering, and a minor in Humanitarian Engineering from The Ohio State University. She started graduate school in the Welding Engineering Program in Spring 2019. Emily worked for the OSU Engineering Diversity Office for over 3 years, with a passion for bringing more women into engineering… and retaining them! She worked as an intern for General Motors during the summer of 2017. Outside of school, interests include; yoga, reading, listening to podcasts, biking, hiking, and relaxing with family (born and raised in Columbus).

Sam Luther

Ph.D. Candidate advised by Dr. Boian Alexandrov

Recreating Ductility-Dip Cracking via Gleeble-Based Welding Simulation

Abstract

Face-centered cubic (FCC) alloys, such as nickel-based alloys and austenitic stainless steels, are important to many industries, notably nuclear power generation and petrochemical. These alloys are prone to ductility-dip cracking (DDC), an intermediate-temperature, solid-state cracking phenomenon. They experience an abnormal elevated temperature ductility loss, which leads to cracking upon applying sufficient restraint. A unified mechanism for DDC has been elusive. To learn more about DDC, an experimental procedure has been designed and evaluated for use in future studies. It is a thermomechanical test which replicates welding conditions via fixed-displacement thermal cycling (FDTC) using the Gleeble™ thermomechanical simulator. 

This study evaluates FDTC and aims to establish the procedure is reproducible and adequately optimized for producing DDC. A design of experiments (DOE) was created with four alloys tested at varying preloads, elevated temperature strains, and number of thermomechanical cycles. Mechanical energy imposed within the DDC temperature range was used for quantification of the effect of thermomechanical cycling on the DDC response. The materials tested were 310 stainless steel and nickel 201 base metals, and nickel-based filler metals 52M and 52MSS. FDTC has been optimized to include elevated temperature straining, no preloading, and samples made entirely of weld metal for uniform stress/strain distribution.

Bio

I am a Ph.D. student studying welding engineering in the Materials Science and Engineering Department at The Ohio State University. My research interests include ductility-dip cracking, nickel-based metallurgy, and interfacial thermodynamics. Before graduate school, I completed my B.S. in welding engineering at OSU and graduated summa cum laude in May of 2016. I have interned with DuPont Industrial Biosciences, Bettis Atomic Power Laboratory, and Tosoh Specialty Metals Division and served as a TA and undergraduate research assistant at OSU.

Web site: cwe.engineering.osu.edu

In my free time, I enjoy rock climbing, gaming, and reading. The best rock climbing gyms around are Vertical Adventures and Chambers, go to OSU if you would like to climb with training wheels on. The best game is Path of Exile, an action role-playing game similar to Diablo. PC games only. The best book is the Tao Te Ching by Laozi (also known as Lao Tzu or "The Old Master"). I like to be challenged; rock climbing challenges my body, books challenge my mind, and games challenge my patience (sometimes).