Deformation Behavior and Precipitation Features in a Stretched Al-Cu Alloy at Intermediate Temperatures.

Abstract

Deformation behavior and precipitation features of an Al–Cu alloy are investigated using uniaxial tensile tests at intermediate temperatures. It is found that the true stress drops with the decreased strain rate or the increased deformation temperature. The number of substructures and the degree of grain elongation decrease with the raised temperature or the decreased strain rate. At high temperatures or low strain rates, some dynamic recrystallized grains can be found. The type of precipitates is influenced by the heating process before hot tensile deformation. The content and size of precipitates increase during tensile deformation at intermediate temperatures. As the temperature increases over 200 °C, the precipitation process (Guinier Preston zone (G.P. zones)→θ′′ phase→θ′ phase) is enhanced, resulting in increased contents of θ′′ and θ′ phases. However, θ′′ and θ′ phases prefer to precipitate along the {020}Al direction, resulting in an uneven distribution of phases. Considering the flow softening degree and the excessive heterogeneous precipitation of θ′′ and θ′ phases during hot deformation, the reasonable strain rate and temperature are about 0.0003 s−1 and 150 °C, respectively.