%0 Journal Article
%T Modification of Magnesium Alloys by Ceramic Particles in Gravity Die Casting
%A Urs Ha£¿linger
%A Christian Hartig
%A Norbert Hort
%A Robert G¨¹nther
%J International Journal of Metals
%D 2014
%R 10.1155/2014/748595
%X A critical drawback for the application of magnesium wrought alloys is the limited formability of semifinished products that arises from a strong texture formation during thermomechanical treatment. The ability of second phase particles embedded into the metal matrix to alter this texture evolution is of great interest. Therefore, the fabrication of particle modified magnesium alloys (particle content 0.5¨C1 wt.-%) by gravity die casting has been studied. Five different types of micron sized ceramic powders (AlN, MgB2, MgO, SiC, and ZrB2) have been investigated to identify applicable particles for the modification. Agglomeration of the particles is revealed to be the central problem for the fabrication process. The main factors that influence the agglomerate size are the particle size and the intensity of melt stirring. Concerning handling, chemical stability in the Mg-Al-Zn alloy system, settling and wetting in the melt, and formation of the microstructure in most cases, the investigated powders show satisfying properties. However, SiC is chemically unstable in aluminum containing alloys. The high density of ZrB2 causes large particles to settle subsequent to stirring resulting in an inhomogeneous distribution of the particles over the cast billet. 1. Introduction Due to their low density and their high specific strength magnesium wrought alloys reveal great potential for light weight applications in the transportation industry. Nevertheless, magnesium wrought alloys still exhibit a few drawbacks which make their application difficult. One is the limited formability of semifinished products like sheets that arises from a strong texture formation during the thermomechanical treatment. To overcome this drawback a significant part of current research on magnesium wrought alloys aims at designing alloys that show an altered recrystallization behavior. For this purpose those recrystallization mechanisms in magnesium wrought alloys have to be identified and fully understood that can change the texture evolution. A possible recrystallization mechanism that is mainly known from other metals is the so called particle stimulated nucleation (PSN) [1]. Although PSN in magnesium wrought alloys is not fully understood, Laser [2] has shown that basically it works. Typically, the starting material for the thermomechanical treatment is produced by casting and particles are created by adding alloying elements to the melt that form precipitates. However, precipitates exhibit several disadvantages that complicate the systematic investigation of the influence of particles
%U http://www.hindawi.com/journals/ijmet/2014/748595/