Plastic behaviour of quasicrystals and related intermetallic phases

In the present work, the plasticity of quasicrystals, metallic glasses and structurally complex alloy phases was investigated. The concepts of plasticity for simple crystalline materials cannot be applied to these materials without substational modification. Plastic deformation experiments and subsequent microstructural investigations by means of transmission electron microscopy (TEM) were performed on icosahedral Zn-Mg-Dy and Al-Pd-Mn single quasicrystals. A constitutive model approach describing the plasticity of icosahedral quasicrystals was applied to a wide range of experimental deformation parameters. In both materials plastic deformation depends on the interaction of dislocation storage and recovery and the strain driven disordering and diffusion driven reordering of the material. The plastic deformation behaviour of Pd-Ni-Cu-P bulk metallic glass was studied in creep experiments at three different temperatures and in a wide range of creep stresses. The transition between steady-state creep and accelerating creep was studied. Based on the free-volume description a constitutive model was developed, which comprehensively describes the salient features of metallic-glass plasticity for various deformation conditions. Furthermore dislocation-like defects in the structurally complex alloy phases Xi'-Al-Pd-Mn and c2-Al-Pd-Fe were investigated. New types of defects, which are present in the materials after plastic deformation, were found and characterized by means of TEM. It was shown that the basic concepts of dislocation-like defects show clear similarities in both structurally complex phases