October_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | O C T O B E R 2 0 1 7 1 3 REDUCING OXYGEN FORTIFIES NANOCRYSTALLINE MATERIALS Researchers at the University of Connecticut discovered that reducing oxygen in some nanocrystalline mate- rials may improve their strength and durability at elevated temperatures, a promising enhancement that could lead to better biosensors, faster jet en- gines, and greater capacity semicon- ductors. Using a special milling process in an enclosed box filled with argon gas, UConn scientists, working in collabora- tion with researchers fromNorth Caroli- na State University, were able to synthe- size nanosized crystals of iron-chromi- um and iron-chromium-hafnium with oxygen levels as low as 0.01%. These nearly oxygen-free alloy powders ap- pear to be much more stable than their commercial counterparts with higher oxygen content at elevated tempera- tures and under high levels of stress. Grain size stability is import- ant and studies have shown that smaller grains are better when it comes to making stronger and tougher metals that are less prone to cracking, better con- ductors of electricity, and more durable at high temperatures and under extreme stress. Re- cent advances have enabled de- velopment of grains at the scale of just 10 nm, but the process is not perfect. When some nano- grains are created in bulk for ap- plications such as semiconduc- tors, the stability of their size can fluc- tuate under higher temperatures and stress. It was during the investiga- tion of this instability that the UConn team learned about the role oxygen plays inweakening nanocrystal stability at high temperatures. Moving forward, the researchers intend to test their the- ory on other alloys to see whether the presence or absence of oxygen impacts performance at elevated temperatures. today.uconn.edu . POROUS ALUMINUM IS UNSINKABLE A new technology for producing an unsinkable material made of aluminum alloy was recently patented at Peter the Great St. Petersburg Polytechnic Uni- versity in Russia. Porosity is achieved by adding foaming gas into liquid met- al during remelting of the aluminum. The porous materials can be used to in- crease structural stiffness, as well as for soundproofing and heat insulating, say researchers. “The high porosity level can be used to decrease the density of struc- tural elements, e.g., sheets. The density can be decreased even lower than that of water, and its use in shipbuilding will ensure unsinkability even with a leak in the hull,” says Oleg Panchenko, deputy head of the Laboratory of Light Mate- rials and Structures SPbPU, one of the inventors. In many cases, the carrying ca- pacity of thin materials (1 mm or less) is sufficient for structural integrity. But material with such nominal thickness sometimes has geometric limitations (the thickness is too small for manip- ulation) or it cannot be joined without deformation. Due to pores in the new material, it is possible to increase the thickness while maintaining the weight and increasing structural stiffness. A similar technology has been patented in Japan, but a specific feature renders the resulting material entirely porous. The SPbPU researchers have found a way to produce both homogeneous and heterogeneous pore distribution, so that the solid material can be ei- ther significantly porous or, with thick- ening, become a more solid structure. www.english.spbstu.ru. PROCESS TECHNOLOGY Unsinkable material made of aluminum alloy. Courtesy of Peter the Great St. Petersburg Polytechnic University. UConn researchers work with a glove box to produce nanomaterials. BRIEF Spirit AeroSystems, Wichita, Kan., opened a new 3- and 4-axis machining center at its McAlester, Okla., facility. Equipment includes 18 new machines purchased from a fabrication shop in Juarez, Mexico. Spirit acquired the ma- chines to add soft metal machining capacity. The center will specialize in small to medium-sized parts and will come online later this year. spiritaero.com .