NEXT MEETING
March 17, 2022, 7:00-8:15PM (EST)
featuring
👩🏻‍🎓Dr. Scott Julien (15 min)
Postdoctoral Fellow, Northeastern University, MA
"Bulk Fracture Anisotropy in Cold-Sprayed Al 6061 Deposits"
followed by
💥Prof. Ivan Petrov (60 min)
Department of Physics, Linkoping University, Sweden
"Recent Advances in Surface Engineering​"

                                                          Main Talk
​Surface Engineering (SE) is the science and technology of improving the surface properties of materials for protection in demanding contact conditions and aggressive environments. SE also encompasses engineering new multi-functional surface properties, such as electrical, optical, thermal, chemical, and biochemical properties. It involves multiple or hybrid processes which include substrate modification and deposition of overlayers in complex architectures.  These processes enhance adhesion and optimize composition or microstructure to enhance protective properties coupled with other functionality. The substrates may be of complex shapes, like metal-cutting tools and automotive or aerospace components, and range in size from micrometers, such as in MEMS or NEMS (micro- or nano-electromechanical systems) devices, to meters, such as in architectural glass. The applications are wide-ranging, and include, for example, control of friction, wear-resistance, corrosion-resistance, thermal-barrier coatings, decorative coatings, bioimplants, antimicrobial layers, web-coatings, and thin films with engineered electrical and optical responses. Areas of scientific interest range from first-principle atomistic studies of new materials, which are both hard and ductile, (i.e., tough), to scientific and technological advances in synthesis methods, structural and chemical characterization techniques, property measurements, and performance characterization of surface-engineered parts. Several recent advances in magnetron sputter-deposition of protective coatings will be highlighted and discussed.​

Dr. Ivan Petrov is a Professor of Physics at Linköping University, Sweden and Visiting Professor of Materials Science at the National Taiwan University of Science and Technology. He was a Professor of Materials Science and Principal Research Scientist at the Frederick Seitz Materials Research Laboratory (1998-2010), and Director of the Center for Microanalysis of Materials at the University of Illinois at Urbana-Champaign. He was a Visiting Professor of Surface Engineering at Sheffield Hallam University, UK (2000-2012). Ivan earned his Ph.D. in Physics from the Bulgarian Academy of Sciences and received the Doctor Honoris Causa Degree from Linköping University, Sweden. His research interests include nanostructural and nanochemical analyses, thin film physics, and surface science and engineering. Ivan conducted the first systematic study of the effects of ion/metal flux ratio and ion energy on microstructure evolution in hard coatings, employing a combination of analytical techniques.  He was a co-principal investigator in the US Department of Energy Transmission Electron Aberration-corrected Microscope (TEAM) project which achieved 50 pm resolution. He has published over 350 refereed papers cited > 21000 times with H-index of 73. His review article on Microstructural Evolution of Thin Films has > 1800 citations. Ivan is an Editor of Surface and Coatings Technology and member of the editorial board of AVS Quantum Science. Ivan is a Fellow and Honorary Member of AVS and received the 2009 Bunshah Award and Honorary Lecture from the Advanced Surface Engineering Division and the 2013 AVS John Thornton award and Honorary Lecture. Ivan served as 2015 AVS President.

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                                             Introduction Talk
​Cold spray additive manufacturing is a relatively recent technology for depositing metal and other materials of interest using powdered feedstock at temperatures below the melting point.  It is of especial interest in the repair of aerospace and other specialized materials, where high-temperature processes are either undesirable or infeasible.  However, the use of cold spray to produce structural components and repairs requires knowledge of the load-bearing capacity of cold spray deposits, such as the tensile, fracture, and fatigue properties.  In this work, the tensile and fracture anisotropy in helium-sprayed bulk Al 6061 cold spray deposits were studied.  Tensile properties (elastic modulus, yield strength, tensile strength, and elongation at break) were measured in the two in-plane principal deposit directions (long-rastering, and stepping), and fracture toughness was characterized for six principal load/crack direction pairs defined with respect to the spray directions.  The results showed that no in-plane anisotropy was measured for the tensile properties, which was attributed to uniform in-plane microstructure.  Fracture toughness was found to be mildly transversely isotropic, with equal values when crack propagation was in-plane (mean of 11.0 MPa√m) and slightly higher values when crack propagation was out-of-plane (through the deposit thickness, mean of 13.0 MPa√m).  The overall fracture toughness range was 40-50% that of wrought Al 6061-T6.  In-plane fracture was almost completely interparticular (fracture along particle interfaces), while out-of-plane fracture was a mixture of interparticular and transparticular (fracture through particles).  A greater amount of transparticular fracture was observed in orientations with higher toughness.  Overall, the low level of anisotropy was attributed to good interparticle bonding as a result of effective spray parameters and the use of helium as the accelerating gas.
​

​
Scott Julien is a post-doctoral fellow in the Cold Spray Additive Manufacturing group at Northeastern University, where he researches the fracture properties, shape evolution, and residual stress buildup of cold spray deposits.  He received is B.S. in mechanical engineering from the Missouri University of Science and Technology (Rolla, MO, USA) in 2006 and his M.S .and Ph.D. degrees from Northeastern University (Boston, MA, USA) in 2017 and 2020, respectively.  His current research focus is on characterizing the shape evolution of cold spray deposits using in situ laser profilometry, as well as measuring and modeling the buildup of residual stresses in cold spray deposits using X-ray diffraction and finite element analysis.

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LOCATION AND SCHEDULE for 2021-2022 Season
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                     7:00 PM - 8:15 PM    Intro (15 min) + Main Speaker (60 min)

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