| dc.description.abstract | Utilizing the microstructure analysis instrument such as OM, SEM, TEM, etc., to explore the Influence of mechanical and (exfoliation, stress) corrosion resistance properties of Al-9Zn-2.3Mg-1.9Cu (AA7056) forged alloys by continuously heated non-isothermal aging. The results show that for the thin materials (2mm), discontinuous grain boundary equilibrium precipitates (η-MgZn2) and the fine grain precipitates (metastable η′-MgZn2) can be obtained through the regression and re-aging treatment (namely T77). The strength is only slightly lower than that of the T6 state, but it improves the corrosion resistance of the alloy. But for the thickt piece (120mm), the alloy could not reach the regression treatment temperature at the set time (30min), thus limiting the application of T77 to the thick alloys.
Compared with T77 treatment, non-isothermal aging (NIA) treatment can produce discontinuous equilibrium η-MgZn2 precipitates at the alloy grain boundaries under a shorter time, while the precipitates of the metastable η′-MgZn2 in grains are more finer, not only the strength is similar to that of T77, but also the corrosion resistance of the alloy is significantly improved, and the NIA is less affected by the thickness of the alloy. During the process, the difference between the actual temperature inside and outside the alloy and the set temperature is very small. Therefore, the aging time of AA7056 treated by NIA is shorter than that of T77, and better strength, anti-corrosion, can be obtained. The combination of properties can also overcome that T77 cannot handle thick materials. | en_US |