| Abstract: | In this work was concluded that it is possible to obtain stable in situ composites of Al-Cu-Fe and Al-Cu-Co alloys with reinforcement containing quasicrystalline phases by the mIFC and Bridgman methods. The chemical compositions and technological parameters of processes for which it is possible to obtain stable CQ composites were determined. The composites morphology (especially reinforcement morphology) was examined for different parameters of obtaining process. The materials for investigations were obtained in several stages using two different methods: the Bridgman method and the modified Inclined Front Crystallization (mIFC) method. In the first stage initial composition was chosen based on the Al-Cu-Fe and Al-Cu-Co equilibrium diagram. The composite was studied using X-ray and electron diffraction, light-optical and scanning electron microscopy, X-ray topography and Laue diffraction. Specially prepared composite samples were subjected to uniaxial tension tests using a tensile testing machine in static conditions. Chemical microanalysis was performed using scanning
electron microscope, equipped with an energy dispersive X-ray spectroscope. Using lightoptical
and scanning electron microscopes the morphology of reinforcement was specified.
Based on the results of investigations, it was assumed that the composites of Al-Cu-Fe alloys have a reinforcement in the form of fibres with a rhomboidal cross-section, growing paralel to the solidification direction. In the case of composites based on Al-Cu-Co alloys, fibres have an irregular shape in cross-section and grow at some angle to the solidification direction. Both types of reinforcement include the quasicrystalline phase, respectively: icosahedral i-phase and decagonal D-phase. The fiber growth model was developed based on the redistribution of Aluminum concentration in the diffusion area on solidification front. Laue examination
showed the presence of single-crystalline phase in the composite. This phase was the matrix
of the composites. For some parameters of the Bridgman process, two-scale composites of Al-Cu-Co alloy were obtained. Such composites are characterized by two types of reinforcement with different scales of fiber diameters: nano-scale and micro-scale. The specimens were studied by the X-ray topography during uniaxial tension tests. CQ composites in the uniaxial tension test fractured by brittle mechanism. |