Authors: Vitor L Sordi Carlos A Feliciano Maurizio Ferrante
Publish Date: 2014/09/03
Volume: 50, Issue: 1, Pages: 138-143
Abstract
Severe plastic deformation SPD processes reduce drastically the grain size of metals leading to a substantial increase of mechanical strength Additionally it has been observed that the precipitation kinetics in some Al alloys is accelerated after SPD and thus suitable heat treatments can be used as a strategy for further hardening In this work an Al–17 Ag alloy was processed by equalchannel angular pressing ECAP and aged at 400 °C for different lengths of time with the purpose of observing and quantifying the kinetics of precipitation and competitive growth of the Al2Ag phase as well as the precipitate fracturing and dissolution by ECAP Microstructure observation of samples aged before ECAP deformation showed that precipitate bending rather than fracturing was the dominant event The Al2Ag plates precipitation kinetics were studied on samples aged in the coarsegrained condition and after ECAP results show that in the former group of samples the kinetics is well described by the Ham Horvay and Cahn analysis In the ECAP processed samples a much faster than expected Ostwald ripening type of growth was observed Such behaviour was attributed to a dislocation substructure stabilized by the Al2Ag precipitates overlinel and barl 0 are respectively the precipitate average diameter after t and t 0 ageing time γ the precipitate/matrix interface energy 05 J m−2 and V m the molar volume 1 × 10−5 m3 mol−1 R is the universal gas constant 84 J mol−1 K−1 and T is the ageing temperature 673 K A C 0 and D were defined in the text For the calculation barl 0 and t 0 were equated to zero
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