Over-ageing of an Al-Mg-Si alloy with silicon excess

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:730

Article

Meyruey, G.¹  Massardier, V¹  Lefebvre, W.²  Perez, M.¹ 

[1] Univ Lyon, INSA Lyon, MATEIS UMR CNRS 5510, 25 Ave J Capelle, F-69621 Villeurbanne, France

[2] Normandie Univ, Grp Phys Mat, CNRS, INSA Rouen,UNIROUEN, F-76000 Rouen, France

关键词: Aluminium alloy;    Ageing;    Precipitation;    Thermoelectric power;    Transmission electron microscopy;    Atom probe tomography;    Hardness;    JMAK modelling;   

DOI  :  10.1016/j.msea.2018.05.094

来源: Elsevier

【 摘 要 】

The over-ageing of an Al-Mg-Si alloy with Silicon excess was investigated using global thermoelectric power (TEP) and hardness measurements combined with local techniques (Transmission Electron Microscopy (TEM) and Atom Probe Tomography (APT)), in order to highlight how the peak-aged microstructure obtained by a T6 treatment evolves in use conditions at temperatures between 100 degrees C and 350 degrees C, leading to a progressive loss of mechanical strength. First, TEP was found to be relevant to study the over-ageing kinetics of the alloy due to its perfect correlation with hardness and its sensitivity to the microstructural changes occurring after peak hardness. Then, APT and TEM observations clearly showed that over-ageing is due to the progressive replacement of the beta '' phase by a succession of different types of semi-coherent phases (firstly, of Type B and then of Type A and Type C) and by an extensive precipitation of pure silicon particles. At the highest temperature (T = 350 degrees C), it was highlighted that the influence of manganese cannot be neglected. From these studies, an experimental Isothermal Transformation Curve could be proposed in the investigated temperature range. Lastly, the decrease in mechanical strength taking place during isothermal and non-isothermal ageing from a T6 state was experimentally characterised and successfully analysed using the JMAK formalism.

【 授权许可】

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