F. Palm, EADS Innovation Works Germany, Munich, Germany; R. Leuschner, T. Schubert, Fraunhofer Society, Institute for Manufacturing and Advanced Materials (FhG-IFAM), Dresden, Germany
At AEROMAT2006 in Seattle a new engineering material concept basing on hyper-eutectically Sc alloyed AlMgMn was revealed. Its principle metallurgy originates from super-saturation of the AlMg matrix with Sc and Zr which requires fast cooling procedures during solidification. Due to its very high aging response (0.1 wt% Sc can generate 50 MPa strength increase) “soft” Al-alloys like AlMg4.5Mn (AA5083) can be reinforced by more than 300% in terms of yield strength without sacrificing their renowned manufacturing propensities. Currently 2 variants of the Scalmalloy family are under investigation to refine and extend their property fields: Scalmalloy, a melt spun powder material, net shaped by standard extrusion procedures into profiles
ScalmalloySC, a twin roll or belt strip cast sheet material
“Freezing” of more than 1,0 wt% Sc in the Al-lattice is very difficult. Only improved melt spin procedures developed in close collaboration with the Fraunhofer Institute for Manufacturing and Advanced Materials (FhG-IFAM, Dresden) can cope with this premises. Consequently a AlMg3,6Sc1,4ZrMn alloy is capable to develop hardness values (HV) beyond 220 using heat treatments complying with the specific precipitations kinetics of AlSc-type materials. Extraordinary high room temperature strength always coupled with good ductility reflecting such hardness values were measured.
The patended ScalmalloySC sheet material manufacturing procedure differs significantly from “classically” rolled AlMgSc sheet materials known from Russia (i.e. RUS1570), Germany (ALERIS KO8242) or the US (ALCOA C557). As its strength is derived mostly from precipitation hardening via Al3ScZr and not from strong cold rolling it can develop a unique combination of fracture toughness and high yield strength. Hence low cost and corrosion resistant airframe shell structures with very good properties might become feasible.
Summary: Scalmalloy® is a unique high strength AlMgSc type material solution which relies on rapid solidification and a hypereutectically alloyed Al-Sc metallurgy. It owns the well known appreciated processing properties of Sc free 5xxx material (like 5083) but displays more than twice of that strength
