Microstructure and Properties of Cast Ingots of Al-Zn-Mg-Cu Alloys Modified with Sc and Zr

摘要

The effect of combined additions of Sc and Zr on the microstructure and tensile properties of the direct chill (DC) cast ingots of developmental Al- Zn-Mg-Cu alloys has been evaluated in this work. The properties in both the longitudinal and transverse directions of the cast ingots were determined in as- cast and cast plus heat-treated conditions, at room and cryogenic temperatures. Extensive microstructural evaluation was carried out using optical and electron microscopy, including orientation image microscopy by the electron backscatter diffraction technique. The Sc-containing developmental cast alloys showed the tensile properties, which are much better than the properties of any commercial cast Al alloys and are similar or even superior to the properties of 7075-T6 alloy forgings. The microstructural evolution, the strengthening mechanisms, optimum content of the dispersoid-forming elements, and the processing- structure-property correlations are discussed.