X-RAY DIFFRACTION STUDY ON LATTICE CONSTANT OF SUPERSATURATED SOLID SOLUTION FOR AL BASED BINARY ALLOYS AND SELECTED AL-ZN-MG-CU ALLOYS

摘要

The effects of Zn, Mg, Cu content on lattice constants of the supersaturated solid solution of Al- Zn, Al-Mg, Al-Cu based binary alloys and three selected 7B04, 7050, 7B85 alloys were investigated by using X-ray diffraction pattern technique, and the effect of lattice distortion on the stability of the solid solution was attempted to describe the mechanism of quench sensitivity in age hardened Al alloys. The results show that the Cu is most sensitive to the lattice distortion of Al matrix when it was added to Al alloy to form supersaturated solid solution. The effect sequence of alloying elements to lattice constant of the 7XXX series aluminum alloy solid solution was: Cu > Mg > Zn. Evidence has been presented for the obvious expansion behavior of Al lattice in the supersaturated 7B04, 7050, and 7B85 alloy. The order of the lattice distortion of solid solution of was: 7B04 > 7050 > 7B85. Compared to the 7B04 and 7050 alloy, the main alloying elements seems to be most stable in the solid solution of 7B85 alloy, and this could be used to explain the lowest quench sensitivity of 7B85 alloy among three selected 7XXX series alloys in this study.