Abstract
In the present study, microstructural and mechanical properties of EN AW 7075 following stress-aging were assessed. For this purpose, properties of stress-aged samples were compared with values obtained for conventionally aged counterparts. It is revealed that the strength and hardness of EN AW 7075 can be increased by the presence of external stresses during aging. Precipitation kinetics were found to be accelerated. The effects of conventional and stress-aging on the microstructure were analyzed using synergetic techniques: the differently aged samples were probed by differential scanning calorimetry (DSC) in order to characterize the precipitation processes. DSC was found to be an excellent screening tool for the analysis of precipitation processes during aging of this alloy with and without the presence of external stresses. Furthermore, using electron microscopy it was revealed that an improvement in mechanical properties can be correlated to changes in the morphologies and sizes of precipitates formed.
Highlights
Since many years, attempts have been made to substitute steels with alloys of low density to eventually reduce the weight of manufactured components
The effect of artificial aging under superimposed external stresses on the mechanical properties and microstructure of EN AW 7075 alloy was explored in present work
Hardness and tensile tests revealed that stress-aging led to an enhanced peak strength of EN AW 7075 alloy
Summary
Attempts have been made to substitute steels with alloys of low density to eventually reduce the weight of manufactured components. Efforts have been made to increase the strength of aluminum alloys by the employment of different thermo-mechanical processing routes In these studies, the focus remained on precipitation hardening/aging since this heat treatment allows to establish parts with high strength and adequate ductility. At aging temperatures above 200 ◦ C and increased aging times, respectively, η (MgZn2 ) phase can be formed along the grain boundaries (GBs), subgrain boundaries or even in the grain interior, while higher temperatures and longer duration further promote coarsening of the precipitates [20] Another important parameter in age hardening of this alloy is the cooling rate from SHT. Aging temperature, duration and cooling rate from SHT are critical parameters in the precipitation process of aluminum alloys eventually allowing to directly design microstructure and final mechanical properties. The obtained results provide pathways to realize superior components made of high strength aluminum alloys
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