Microstructure and vacancy-type defects of high-pressure torsion deformed Al-3 wt%Cu alloy

Abstract

The influence of high-pressure torsion (HPT) on the microstructure and free-volume type defects of supersaturated Al-3 wt%Cu was studied. By means of HPT, grain refinement down to sizes of 100 nm could be achieved. Positron annihilation spectroscopy was applied for the characterization of deformation-induced defects and of vacancy-solute interaction. The chemical sensitive method of two-dimensional Doppler broadening spectroscopy reveals predominantly deformation-induced defects. In comparison to undeformed supersaturated Al-3 wt%Cu, the fraction of Cu-decorated free-volume type defects is strongly reduced and Al2Cu-precipitates with equilibrium structure occur rather than metastable semi-coherent Al-Cu precipitates. These precipitates stabilize the nanocrystalline structure and give rise to a rather different aging behaviour compared to the undeformed state.

Effect of Homogenization Treatment on the Microstructure and Mechanical Property Evolutions of As-Cast Al–Cu Alloy during High-Pressure Torsion

“…The average grain size of the present HPT-processed as-cast Al Cu alloy sample was very close to the reported average grain sizes (70 and 100 nm) in the HPT processed Al-2024 and Al3%Cu alloys, respectively. 22,27) The SAED pattern of the HPT-processed as-cast AlCu alloy sample shown in Fig. 2 indicates the presence of low misorientation angle grain boundaries (LAGBs).…”

Acceleration of volume decomposition of supersaturated Al + 4 wt.% Cu solid solution under irradiation with Ar+ ions

“…A particularly good example of the above is accelerating solid solution decomposition in alloys subjected to severe plastic deformation (SPD). SPD activates the decomposition and changes its stagewise character as indicated in a number of papers .…”

“…For example, it is shown in Ref. that particles of a stable θ ‐phase (Al 2 Cu) from 50 to 200 nm in size with an average distance between them of about 800 nm are formed at grain boundaries and triple junctions in Al + 3 wt.% Cu alloy after deformation by high pressure torsion, quenching, and subsequent annealing for 144 h at 190 °C, whereas semicoherent lamellar θ ′‐phase particles with a size and average distance between them of about 200 nm precipitate in the undeformed alloy under the same quenching and annealing conditions.…”

Charging-induced defect formation in LixCoO2 battery cathodes studied by positron annihilation spectroscopy

“…33%, and therefore a positron lifetime component for the Al substrate (165 ps (Ref. 19) for defect-free Al) with the corresponding intensity was numerically subtracted from each positron lifetime spectrum upon analysis. For Doppler broadening this correction could be omitted since for further discussion only relative variations of the integral S and W parameters upon Li þ -extraction on a qualitative base are of relevance.…”