Nov_Dec_AMP_Digital

7 2 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 | N O V E M B E R / D E C E M B E R 2 0 1 7 3D PRINTSHOP NANO-FUNCTIONALIZED POWDERS SOLVE HOT CRACKING PROBLEM Engineers at HRL Laboratories LLC, Malibu, Calif., developed a way to eliminate hot cracking in 3D-printed parts made of high-strength aluminum, including 6061 and 7075. Uncontrolled cracking during solidification current- ly prevents thousands of commercial alloys from being used in additive manufacturing. The ingenious fix de- veloped by HRL engineers alters the solidification dynamics of the alloy by adding nanoparticles to the powder. The particles act as nucleation sites, optimizing lattice alignment between adjacent grains and enabling formation of uniform, crack-free, fine-grained mi- crostructures, comparable in strength to wrought materials. Besides alumi- num, the method also applies to high- strength steels and nickel-base super- alloys as well as other metals that are difficult to weld or print. hrl.com . A direct-write 3D printer dispenses a silicone ink infused with gas-filled pores (inset) that expand when heated and contract when cooled. Developed by LLNL researchers, the ink may one day be used to create formfitting cushioning activated by body heat. AIRBUS INSTALLS FIRST 3D-PRINTED TITANIUM PART ON COMMERCIAL FLEET Airbus, France, is instal- ling 3D-printed titanium bra- ckets on production units of its A350 XWB, the first such use of additively manufac- tured parts in the aerospace industry. The brackets are part of the pylons that hold the engines to the wings, and their use on a commer- cial airframe represents a significant advancement in the qualification of print- ed metal components for aerospace applications. The structurally critical parts are manufactured by Arconic, New York, a long-time Airbus supplier of titanium and nick- el components made using laser pow- der bed and electron beam technology. airbus.com . A production specialist works on a 3D-printed titaniumbracket, part of a pylon assembly designed for the Airbus A350 XWB. RESEARCHERS PRODUCE 4D-PRINTED MATERIAL Researchers at Lawrence Liver- more National Laboratory, Calif., de- veloped a printable silicone ink that possesses shape memory properties. The activating mechanism, discovered by accident while testing porous ma- terials, is an expanding gas trapped in polymer-lined pores embedded in the ink. The polymer has a glass transition temperature, below which it is rigid and glassy, and above which it becomes soft and malleable. As a result, objects made from the ink can be compressed at elevated temperatures and will re- main in that state as they cool. When reheated, however, the gas expands in the tiny balloons, forcing the overall structure to return to its original shape. Researchers envision applications in athletic equipment, such as helmets, braces, and shoes, and potential large- scale uses in packaging, transportation, and load stabilization. llnl.gov. An aluminumpiston made with nano-functionalized 6061 powder (inset) shows no signs of cracking or shrinkage, a problem that currently prevents thousands of alloys frombeing used in additive manufacturing.