✍ Scribed by D.M. Riley; P.G. McCormick
No coin nor oath required. For personal study only.
The influence of precipitation hardening on the characteristics of serrated yielding in an Al-IMg-Si alloy has been investigated. The critical strain at the onset of serrated yielding was increased by ageing and for ageing times longer than 6 hr at 180°C serrated yielding was not observed. The strain ageing time for solute locking was found to increase on ageing for 1 hr and remain constant with further ageing to 1 hr. The exponent of strain. m f /3, in the critical strain-strain rate refation was also increased by ageing. The results are discussed in terms of changes in the matrix solute concentration, the rate controlling obstacles. and the obstacle spacing accompanying the ageing process.
Resume--On a etudie I'intluence du durcissement par precipitation sur les caracteristiquer des discontinuites de la contrairte dans un alliage Al-Mg-Si. La deformation critique pour l'apparition de ces discontinuitts augmentait par revenu. et on ne I'observait plus pour des vieillissements a 1SO'C de duree superieure a 6 h. On a trouve que le temps de vieillissement pour le blocage par le solute augmentait pour un revenu dune heure, et restait constant pour un vieillissement allant jusqu'a 4 h. L'exposant m I-/3 de la deformation dans la courbe deformation critique-vitesse de deformation augmentait aussi par vieiiiissement . On discute ces resultats 6 partis drschangements de la concentration du solute daus la matrice, des. obstacles controlant la vitesse et de l'espacement des obstacles au tours du recuit.
Einflui3 der Ausscheidungsverfestigung auf die Eigenschaften des ruckweisen FlieDens wurde an einer Al-Xfg-Si-Legierung unterrucht. Durch Altern wurde die kritische Dehnung beim Einsatz des ruckweisen FlieDens vergriioert; bei Alterungszeiten grinder als 6 Stunden bei 1SO'C wurde ruckweises FlieBen nicht beobachtet. Die Reckalterungszeit fur Losungsverfestigung wird gri%er bei einsttindigem Altern und bleibt konstant bei llngerem Altern bis 4 Stunden. Der Reckexponent m + p in der Beziehung kritische Reckung-Reckgeschwindigkeit wurde ebenfalls durch Altern ver-grijf3ert. Die Ergebnisse werden auf der Basis von Vednderungen in der Matrixkonzentration geltjster Atome, in den g~ch~vindigke~tsbestimmend~n Hindernissen und in dem den Alterungsprozess begfeitenden H~ndernisabstand diskuriert.
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