| Al-Zn-Mg-Cu alloys played a significant role in aviation industry due to their desirable mechanical properties, e.g. high strength and low density. The effect of Sn addition on cast structure and one-step ageing of Al-Zn-Mg-Cu alloys had been investigated by using Vickers hardness measurement and transmission electron microscope observation (TEM). We were also searching for an appropriate aging process in our research. We get results as fellow:1. Sn addition can refine Al-Zn-Mg-Cu cast alloy grains. While after rolling and solution treatment, refining effect of grains was not so excellent. Sn existed in Al-Zn-Mg-Cu alloys could be in the form of simple substance or Mg2Sn. Therefore, adding too much 7XXX alloy Sn alloys may be negative.2. In this paper, peak strength of single step aging of 0.12% Sn added Al-Zn-Mg-Cu alloys was higher than the strength of other alloys, the fracture strength Gb=602MPa, elongationζ=9.0%。3. Sn addition could promote the formation of GPII zone in the early aging and inhibition of coarsening of precipitates when over ageing.4. Appropriate size and distribution of precipitation could be obtained by pre-aging.120℃×1h+190℃×15min+120℃×34h was the best heat-treat in our research, fine dispersion of intragranular precipitates, discontinue distribution of precipitates at grain boundary, as well as good performance could be obtained by this method. |
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