CREEP-FATIGUE BEHAVIOUR OF REINFORCED MECHANICALLY ALLOYED SYSTEM AL - AL4C3
Abstract
The static and load controlled cyclic creep behaviour of dispersion strengthened system Al- Al4C3, prepared by mechanical alloying with 8 vol.% of Al4C3, have been studied. The mutual relationship between mechanical properties and microstructure changes in Al - Al4C3 composite system was charcterized by tensile, creep and cyclic creep tests. The phenomenon of superplasticlike behaviour was observed for static deformation. Different testing procedures of cyclic creep where fatigue stress component was superimposed on creep mean stress were carried out under specific loading schedules defined by stress amplitude, stress range, stress ratio, and cycling frequency. The influence of these variables was evaluated through the deformation and fracture behaviour of of dispersion system. At cyclic creep testing the decreasing of stress ratio Q reflected in definite decrease of the secondary stage elongation. The frequency increase at constant stress ratio Q resulted in life time extension accompanied by higher elongation too. The fatigue stress component superimposed on the creep stress accelerated the deformation and fracture process for testing with lower frequencies. The analysis of the strain and fracture mechanisms in the microstructure has confirmed the onset of polygonization during creep and during cyclic creep the process of dynamic recovery modified the deformation process. At damage process introduction of fatigue stress component into the creep did not reflected neither at crack nucleation nor crack propagation.
Editors and press
AMS online
