Aug 4, 2016 | By Benedict

A team of researchers from the University of Pittsburgh has received a $503,000 grant from the National Science Foundation to study the solidification processes of aluminum alloys, such as those used in additive manufacturing. The study will utilize a one-of-a-kind transmission electron microscope.

3D printing with metals is a fascinating business, one which involves powders, large machines, and laser beams. Metal additive manufacturing processes such as selective laser melting (SLM), selective laser sintering (SLS), and direct metal laser sintering (DMLS) each use laser beams to fuse metal powders into 3D shapes. SLS and DMLS 3D printers heat the metal powders to a sufficient level so that they can fuse together at a molecular level, while SLM 3D printers go one step further, completely melting the metal powder before letting it solidify into the desired shape. All of these methods have been developed into highly effective additive manufacturing techniques, but a team of researchers at the University of Pittsburgh wants to better understand how exactly metals behave during the SLM process and in similar laser-melting processes.

The team, led by Jörg M.K. Wiezorek, PhD, professor of mechanical engineering and materials science at the University of Pittsburgh, has been awarded a $503,000 grant from the National Science Foundation’s Division of Materials Research. With that funding, the scientists will, over the course of three years, be able to use the Lawrence Livermore National Laboratory’s dynamic transmission electron microscope (DTEM) to examine—in real time—how microstructures form in metals and alloys during the solidification process which follows laser beam melting. Such laser beam melting is deployed in welding and joining, as well as additive manufacturing.

Metal powder for additive manufacturing

During the three-year study, Dr. Wiezorek’s team will use the LLNL microscope to record nanoscale transformations in the metal 3D printing alloys with nanosecond time-resolution. Traditional electron microscopes are only capable of taking before-and-after images, so the ability to monitor the materials in real time using the one-of-a-kind apparatus will give the researchers an unprecedented level of insight into the solidification process of aluminum alloys.

“Predicting microstructure formation during rapid non-equilibrium processing of engineering materials is a fundamental challenge of materials science,” Dr. Wiezorek explained. “Prior to advent of the DTEM we could only simulate these transformations on a computer. We hope to discover the mechanisms of how alloy microstructures evolve during solidification after laser melting by direct and locally resolved observation. Thermodynamics provides for the limiting constraints for the transformations of the materials, but it cannot a priori predict the pathways the microstructures take as they transition from the liquid to the final solid state.”

LLNL's dynamic transmission electron microscope (DTEM)

Dr. Wiezorek believes that the research will help to validate computer models and determine the effects of composition changes and temperature gradients on the microstructure of the metal alloys used in additive manufacturing and other processes. The results could help scientists to better understand the relationships between processing conditions, structure, and properties of the laser-processing alloys. “We are hoping to unravel details of the kinetic pathways taken from the liquid to the final solid structure,” Dr. Wiezorek said. “This research will help us to refine solidification related manufacturing processes and to identify strategies to optimize how materials perform.”

The team’s successful research proposal was titled “In-situ transmission electron microscopy of microstructure formation during laser irradiation induced irreversible transformations in metals and alloys.” The grant money will also be used to enhance the materials science curriculum at the University of Pittsburgh and to improve educational outreach programs.



Posted in 3D Printer Company



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