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Workshop / Seminar

MME Seminar: Mechanical property tuning through interfaces modification

Engineering Teaching Research Laboratory, Pullman, WA
ETRL 101
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About the event

Presented by
Tae-Kyu Lee, PhD Associate Professor Department of Mechanical and Materials Engineering, Portland State University

Recent development in additive manufacturing provides a variety of technology for a stable structure build-up. Much of the focus of the additive manufacturing to this point has been on the shape to the exclusion of properties. In multilayer systems mechanical properties are controlled by the properties of the interfaces, which are twofold, interfaces between individual layers and the interfaces between the different processes. These interfaces have high levels of localized residual stress, that plus the small scale of deposition and the heat input from the deposition process can alter phase transformations and recrystallization behavior at the interface. Avoiding high levels of residual stress during the AM process is generally desired.  Alternatively the AM process can trigger unexpected, from a conventional processing perspective, phase transformations, which can have beneficial mechanical properties. Wire feed gas metal arc welding (GMAW) is a technology for high deposition rate suitable for large structures. Especially, Cold Metal Transfer (CMT)  provides low heat input, which resulted in minimized heat affected zone at the layer interface. Combined with a 6-axis robot arm system, it can produce stable and high deposition rate structures with single or multi-material layers. In this presentation, we will look into mechanical stability and microstructure evolution in Cold Metal Transfer (CMT) additive manufactured structures with different CMT arc modes, combination of Electro-spark deposition (ESD) and Ultrasonic impact treatment (UIT). Understanding and controlling the interface properties allows targeted properties to be implanted during building process.  This so called ‘property tuning’, enables the AM component to function as multi-property performer in a single body component, which will be also discussed.