Processing of Wrought Magnesium Alloys
Dietmar Letzig
Magnesium Innovation Centre
Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung GmbH
Max Planck-Str. 1, D-21502 Geesthacht, Germany
Wrought Magnesium alloys, are potential metals to be progressively introduced into structural components in many areas, especially in transportation and electronic industries due to their outstanding specific mechanical properties. Nevertheless, the extensive use of these structural materials is hindered due to some properties, like mechanical anisotropy, tension/compression yield asymmetry, relatively low absolute strength values and poor ductility.
The properties of such structural parts are dependent on the evolved microstructure from the process. A better understanding is needed for outlining the needs in microstructure and texture development for designing suitable properties of wrought magnesium components. A combination of new technologies and innovative alloys could help to alleviate the strong textures formed in semi-finished Mg products.
The presentation will give a general overview on the special needs of wrought processes and a process-specific alloy design. Further, the research activities at the Magnesium Innovation Centre-MagIC will be presented with respect to the above mentioned aspects with a special focus on Magnesium sheet development.
Twin-roll Casting of Mg Alloys
Nack J. Kim
Pohang University of Science and Technology (POSTECH), Pohang, Korea
Lightweighting of automobiles is possible through the application of materials such as advanced high strength steels and low density alloys including Al and Mg alloys. Mg alloys having a density about one-fourth of steel and two-thirds of Al can offer greater weight reduction over other materials, provided that Mg alloys have comparable properties to those of steels and Al alloys. The use of large amounts of Mg alloys in automobiles has been frequently predicted, but their actual application, particularly of sheet products, is quite limited, due to their several shortcomings such as high cost, poor mechanical properties including formability, etc. It has been recently shown that twin-roll casting (TRC) can produce low cost, high quality Mg alloy sheets that have comparable or better mechanical properties compared to those of conventional Mg alloy sheets produced by ingot casting. One of the main advantages of TRC is that it provides much faster solidification rates, 102 to 103 K/s, than the conventional ingot casting, resulting in the microstructure having reduced segregation and refined microstructural features. It also enables the utilization of alloying elements that have limited solid solubilities in Mg. Such elements are usually avoided in ingot casting since at slow solidification rate they form coarse deleterious intermetallic particles. On the other hand, those intermetallic particles can be dispersed in a fine scale in the case of TRC Mg alloys. In this presentation, the recent progress in the development of wrought Mg alloys by TRC will be reviewed with particular emphasis on the fundamental aspects such as microstructure and texture evolution and deformation behavior. Also presented will be some examples showing the applications of TRC Mg alloys in automobiles and the author’s own perspective, which would guide future research aimed at improving the properties and broadening the structural applications of wrought Mg alloys.
Severe Plastic Deformation Processing of Magnesium Alloys:
Past and Current Practices
Laszlo Kecskes
Materials and Manufacturing Science Directorate
Weapons and Materials Research Directorate
Aberdeen Proving Ground, MD 21005-5069
Contributors: Ibrahim Karaman, David Foley, Suveen Mathaudhu, Michael Eichhorst, Norman Herzig, and Ted Hartwig
Imparting magnesium and its alloys with higher strengths while retaining reasonable ductility has remained an engineering challenge. This presentation will review recent strategies relying on severe plastic deformation processing, more specifically, equal channel angular extrusion (ECAE), to develop a high strength, fine grained product, while minimizing texture sensitivity in both pure magnesium and a commercial magnesium alloy, AZ31B. Typically, in ECAE, the limited suite of variables include the temperature, the extrusion rate, the number of passes, and the billet orientation or route on each pass. Results with multi-pass extrusions either under isothermal or step-down temperature conditions will be described. The effect of post-extrusion roll processing on properties will be also included.
