ABSTRACT
The precipitation phenomena and their connection with the microstructure of several Al alloys (Al-Cu, Al-Zn, Al-Ag-Zn, Al-Zn-Mg) are described with respect to the concentration and applied thermal treatment. The alloys were rapidly quenched or slowly cooled from a temperature higher than the solid solution temperature to room temperature. Both quenched-aged and slowly cooled alloys were heated from room temperature to the solid solution state and cooled back to room temperature, and their microstructure and precipitation phenomena were followed in situ by X-ray powder diffraction, e.g., anisotropy of thermal expansion, phase transitions, thermal hysteresis in phase transitions, change of precipitate shape, partial or complete dissolution of precipitates in the matrix, and formation of solid solution. It has been shown that the microstructure strongly depends on the previous thermal history of the alloys.
