Effect of Stepped Solution Treatment on Microstructure and Properties of AA7085 Aluminum Alloy
The effect of stepped solution treatment on the mechanical properties and the microstructure of AA7085 have been investigated compared to AA7050. Optical and electron microscopy observation and electron probe microanalysis were used to analyze the microstructure and tensile fracture surface of AA7085 and AA7050 processed via various treatment schedules. Besides, X-ray diffractometer and differential scanning calorimeter were used to seek the differences of microstructure characters between AA7085 and AA7050. The results indicate that higher content of Zn along with lower content of Mg and Cu and strictly confined Fe and Si made the matrix of AA7085 get a larger single phase and a higher melting temperature of multi-phase eutectics. By using a lower temperature pretreatment, the initial melting temperature of the alloys can be increased. Consequently complete dissolution of remnant constituents was achieved without overheating. Based on thermodynamics statistic theory, the supersaturation degree of the matrix and the density of cavity may be increased with the elevation of the lattermost solution temperature, which resultes in the increase of fracture toughness and optimization of the microstructure after aging.
Zhong Cao, Xueqiang Cao, Lixian Sun, Yinghe He
C. M. Li et al., "Effect of Stepped Solution Treatment on Microstructure and Properties of AA7085 Aluminum Alloy", Advanced Materials Research, Vols. 239-242, pp. 786-792, 2011