Regensburg 2013 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 41: Mechanical Properties II

MM 41.3: Talk

Wednesday, March 13, 2013, 15:30–15:45, H26

Structure and thermal stability of severe plastically deformed Cu84Al16 — •Nazar Ibrahim, Martin Peterlechner, Sergiy Divinski, and Gerhard Wilde — Institute of Materials Physics, Muenster, Germany

Severe plastic deformation (SPD) is an effective tool for production ultrafine grained materials with extraordinary mechanical properties. High strength and relatively good ductility are attributed to their fine microstructure. In this work, structure modification by high pressure torsion (HPT) and the thermal stability of the resulting microstructure are investigated for the Cu*16 at.% Al alloy . For this alloy, a propensity for the formation of five-fold twinning has recently been reported [X.H. An, et al., Scripta Materialia 64 (2011) 249]. Disks of thickness of 0.8 mm and diameter of 10 mm were processed via HPT for 2,5,10 and 20 revolutions at room temperature using an imposed pressure of 6.0 GPa and rotational speed of 1 rpm. Structural and thermal analyses were carried out using X-ray diffraction, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The DSC experiments using constant heating rates showed two exothermic peaks in the temperature range from 30°C to 450°C. After HPT a highly distorted structure was observed, including dislocations, fragmented grains and twins. The twin thickness in Cu84Al16 has been determined from TEM observation to be in the range of 2 to 6 nm. These small thicknesses are in agreement with the low stacking fault energy of the alloy. The results are discussed with respect of the reported five-fold twinning in this alloy.