MateriAlZ Seminar: Saryu Fensin
Friday, March 25th 2022, 11:00 a.m. AZ Time
Saryu Fensin
Materials Scientist
Los Alamos National Laboratory
"Additive Manufacturing for Design and Repair of Materials for Applications Under Extreme Environments
Zoom Link | Passcode: 068545
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Abstract
Additive manufacturing (AM) of metals presents potential niche advantages over traditional manufacturing, with the potential for revolutionary design and production for various applications. Adding material layer-by-layer, AM is capable of building more complex parts, while efficiently using energy, materials, and time as compared to conventional manufacturing methods. With AM, changing processing conditions, such as powder deposition speed, laser power, spot size, layer thickness, in addition to specific material and powder characteristics, leads to variations in the final microstructure, and consequently properties. For example, undesirable defects such as porosity and lack of fusion defects are more likely to develop under certain solidification conditions. For AM processes to be adopted widely in various applications, the effects of these solidification parameters on attaining specific microstructures must be well understood, as the ability to reliably reproducible specific microstructures will dictate the overall performance of a part. Alternatively, these parameters could also be used to optimize and design microstructures with tailored properties for specific applications. While there has been extensive research to understand the relationships between processing parameters and the resulting porosity, efforts to tailor the grain morphology or texture of the material to optimize properties remain scarce. In this work, selective laser melting (SLM) with varying laser power, laser speed, hatch spacing and layer thickness is used to manufacture more than two hundred samples of 316 L stainless steel. Properties that can be rapidly measured such as density and hardness are used as initial parameters to rapidly down-select nine samples out of the initial 200 samples. These 9 samples are then thoroughly characterized and their mechanical response under uniaxial stress conditions measured to determine any correlations between processing parameters and material properties. While these are insightful measurements, to use these materials in applications where they are subjected to extreme loading conditions, it was also important to measure their properties at high strain rates. Hence, in this work, systematic spall recovery experiments are also performed on these 9 samples to determine if any relationships exist between the dynamic strength of the material and the processing parameters. Our work shows that there exists a critical laser power and hatch spacing that does indeed lead to optimum spall strength. The results from these dynamic experiments that open avenues for a material design using AM will be discussed in this talk. Additional work that also uses additive manufacturing (electron beam) to repair metals and the corresponding dynamic behavior of the repaired components will also be discussed in this talk.
Bio
Dr. Saryu Fensin is a recognized authority in the area of the dynamic behavior of materials specifically related to metals and alloys and is currently the team leader for the quasi-static and dynamic behavior of the materials team within the material science and technology division at Los Alamos National Laboratory. She has contributed to and led programs within the Office of Experimental Science (OES) at LANL and also the department of Defense (DoD) to understand how microstructure controls failure in metals and alloys. Her research has especially focused on the role of heterogeneities and defects in this behavior. Her unique skills are related to coupling both experiments and modeling efforts to not only understand the mechanisms that contribute to damage in metals but also implement some of these insights into the current strength and damage models. She has also been recognized for her leadership both internally and externally through awards and accolades. She was given a Defense Programs award for her contributions to the Pu aging program in 2017 and also the prestigious Robert Lansing Hardy Award for her insights into the role of grain boundaries in damage in failure in 2019 by the Metals, Minerals and Material society one of the largest societies for Materials scientists and engineers.