The kind and amount of alloying elements strongly affects the formation of ultrafine-grained microstructures. Aluminum alloys with different amounts of the alloying element magnesium, and a commercially pure aluminum alloy, have been investigated in order to evaluate how the obtained microstructures will affect the mechanical properties. X-ray profile analysis has been used to determine grain size and dislocation density. With increasing amounts of alloying elements, a smaller grain size and a higher dislocation density after severe plastic deformation (SPD) are obtained, which lead to higher hardness and improved fatigue properties.

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New diffusion brazing alloys for single crystalline component repair processes were developed and tested. Germanium was used as the melting point depressing element in these binary brazing alloys with germanium contents between 20 to 23 wt.%. Microstructural analysis has shown that the formation of a single crystalline joint was achieved after extended brazing cycles with these brazing alloys. No secondary phases other than the desired γ´ precipitates were detected within the brazing zone. This result was shown for two parent materials, PWA 1483 and René N5, a first and a second generation superalloy, respectively. The solidification mechanisms and kinetics were examined and show rather distinct deviations from Transient Liquid Phase Bonding theory for binary systems due to the multicomponent diffusion in the present system. Mechanical testing was performed at room temperature via nanoindentation and at elevated temperatures by hot tensile tests. The nanoindentation results show minor differences in hardness and elastic modulus between brazing joints and parent material. Ultimate tensile strengths of more than 90 % compared to the parent material were obtained in tensile testing at 980 °C.

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