Strukturelle Untersuchung der Ausscheidung in einer Aluminiumlegierung mit 1, 1 Gew.-% Zr

Structure and distribution of the precipitates in a highly supersaturated Al-1.1 %Zr alloy were investigated at temperatures between 200℃ and 550℃. In addition to the tetragonal equilibrium phase Al_3Zr an intermediate phase with cubic ordered structure (L1_2-type) was found. At T≧450℃ this phase occurs in the form of coherent spherical particles or, after redistribution of the spheres, as rods in fan shaped arrangement. At T<450℃ this phase is formed by discontinuous precipitation. Both the lattices of the intermediate and the equilibrium phase lie parallel to that of the matrix. The existence of the cubic ordered structure can be explained from the crystal structure of the tetragonal equilibrium phase

Electron Microscope Observations on Rapidly Cast Al-Mn Alloys

An electron microscope observation was conducted on the cell structure of cast Al-Mn alloys in the composition range between 0.1 and 6 wt% Mn. Solidification and cooling rates were high enough to keep nearly all Mn in supersaturated solid solution for all alloys. At concentrations of 0.5% Mn and higher, dislocation arrays were observed along the cell boundaries, while at nodal points small second phase particles could be detected. In general the nature of cell boundaries did not change decisively over the whole composition range investigated, although some changes in the degree of dislocation alignment and the frequency of second phase particles were noticed. Dislocation densities were low in all alloys. This finding is correlated to low microsegregation at the cell boundaries as observed by microprobe analysis