Materials Frontier No.193
Title: Metal Micro-lattices by Sintering of 3D-Printed Metal Particle Inks
Speaker: Professor David C Dunand, Northwestern University.
Date/Time: 2017-9-13, 10:00am
Venue: B214, School of Materials Science and Engineering Building
Inviter: Bing Ye
To create metallic scaffolds or lattices with defined sub-millimeter strut architectures, most existing additive manufacturing (AM) methods use laser or electron beams to locally sinter or melt metallic powders, usually under vacuum. We demonstrate here an alternate method, Extrusion 3D-Printing, consisting of two simple steps. First, metal (or metal oxide)particle suspension (inks)are extruded into linear struts creating self-supporting 3D cellular structures, in air at ambient temperature. Second, these cellular oxide 3D structures sintered, and if in oxide form are reduced to metal via hydrogen reduction.
We describe here micro-lattices made of three metals - iron, nickel and tungsten - created from inks consisting of the respective metal oxides. In all cases, thermochemical reduction and sintering of the 3D-printed oxide scaffolds results in large shrinkages (up to 80% by volume) but without cracking or distortion. For tungsten micro-lattices created from WO3 particle inks, partial sintering creates micro-pores within the struts (advantageous if high surface area is needed), while full sintering of the struts(desirable for mechanical performance) can be achieved through the addition of 0.5 wt% NiO to the slurry, which, once reduced to Ni, accelerates the sintering of the reduced submicron W particles.
We also demonstrate alloyed micro-lattices made from metallic powder inks with shape-memory properties: (i) a blend of elemental Ni, Mn and Ga, resulting in lattices with microporous Ni-Mn-Ga alloy struts showing twinning and (ii) and a blend of elemental Nb and prealloyed NiTi powders, leading to microporous struts consisting of liquid-phase-sintered NiTi-Nb.