Abstract
Microstructural changes of a commercial Al–Mg–Si alloy were studied during artificial aging by in situ Doppler broadening spectroscopy using a high-intensity positron beam. The in situ positron annihilation characteristics at high temperatures differ considerably from the conventionally applied ex situ measurements at low temperatures. Therefore, a more comprehensive view of precipitation processes in Al–Mg–Si alloys is obtained. Further, in situ positron–electron annihilation techniques allow for an investigation of aging processes with increased sensitivity. For the artificial aging temperatures of 180 °C and 210 °C pronounced variations of the Doppler broadening S-parameter reveal (i) the evolution of clusters into larger precipitates and (ii) the time of the formation of ” precipitates and the role of vacancies in connection to this. Towards higher aging times, the transformation from coherent ” to semi-coherent ’ precipitates could be verified. Additional insights are gained by in situ measurements of the S-parameter during the solution heat treatment of the previously overaged sample. Here, the S-parameter reveals both the dissolution of precipitates starting from temperatures of 364 °C and the thermal generation of vacancies.
Highlights
Age-hardenable aluminium alloys have the advantage of low weight and good resistance to corrosion and are being used in an increasingly wide range of industrial applications [1, 2]
Microstructural changes of a commercial Al–Mg–Si alloy were studied during artificial aging by in situ Doppler broadening spectroscopy using a high-intensity positron beam
Al–Mg–Si alloys were developed in the 1920s and appropriate heat treatment methods have been known for a long time [3, 4], the detailed processes controlling the change in hardness during artificial aging are still not fully understood
Summary
Age-hardenable aluminium alloys have the advantage of low weight and good resistance to corrosion and are being used in an increasingly wide range of industrial applications [1, 2]. Abstract Microstructural changes of a commercial Al–Mg–Si alloy were studied during artificial aging by in situ Doppler broadening spectroscopy using a high-intensity positron beam.
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