Plasticity of Quasicrystalline Alloys and their Crystalline Intermetallic Approximants

An overview is given on the microscopic and macroscopic aspects of the plasticity of quasicrystals and their normalcrystalline approximants. Particular emphasis is laid on icosahedral Al-Pd-Mn and normalcrystalline \xi{\prime} Al-Pd-Mn serving as reference materials. The latter is a large unit-cell intermetallic whose atomic structure is very similar to that of the quasicrystal. Both materials deform involving dislocation mechanisms. However, in the case of \xi{\prime} Al-Pd-Mn a combination of partial dislocations and shear-fault lines produces a novel type of defect termed metadislocation. This combination allows the accommodation of shear avoiding the energetically prohibited very large Burgers vectors of full prismatic dislocations in this large unit-cell material. The Burgers vectors found in both materials are identical. This indicates that the Burgers vector modulus is determined by the short-range order structure.

Keywords:

• Quasicrystals
• Intermetallics
• Plasticity
• Dislocations