| Due to high strength, hardness, better corrosion resistance and toughness, machinabilityand weldability, high strength wrought Al-Zn-Mg-Cu serial alloys were widely applied inaerospace and communication. Since the first applicable7075aluminum alloy was developedby the US in1943, some novel7xxx serial Al alloys had been developed by researchers fromvarious countries, through changing the amounts of Zn, Mg and Cu elements, reducing Fe andSi impurities, improving the weight ratio of Zn and Mg and the addition of microelements, e.g.rare earth elements of Zr and Sc. This kind of alloy is attracting more attentions of materialsscientists. It was well known that the improvement of material strength can be attained alongwith the reduction of plasticity, thus strength improvement with no decrease in plasticity canonly be accomplished through grain refinement. Researches of this alloy are mainlyconcentrated on the followings: compositional design; smelting quality control for thereduction of impurity elements and the improvement of microstructure. This work focused onthe improvement of fabrication method of Al-6Zn-2Mg-2Cu alloy, atomization and smeltingwere combined to improve nucleation and grain refinement for enhanced mechanicalproperties.In this paper, starting from the preparation of Al-6Zn-2Mg-2Cu aluminum alloy, thesample is rolled multi-channel after solid solution treatment and single-staged artificial agingtreatment finally. The optical microscopy, SEM observations and tensile tests at roomtemperature were used to study the microstructure evolution of Al-6Zn-2Mg-2Cu aluminumalloy subjected to different heat treatment conditions and aging time after rolling.Investigations showed that the Al-6Zn-2Mg-2Cu aluminum alloy fabricated through thecombination of smelting and atomization is characteristic of refined grain and homogenousmicrostructure, this kind fabrication was proved to be applicable. The microstructure of theAl-6Zn-2Mg-2Cu aluminum alloy can be effectively refine by the granular refiners whichfabricated by atomization have the same composition of the alloy. The grain size as cast isabout50μm. After being solution treated at475°C for1.5h, following multi-pass rolling withtotal reduction of33%and aging at120°C for different time, the aluminum alloy have doublepeaks. The first aging peak is120°C for40h, and the yield strength was592MPa, peak stressof597MPa and elongation of12.2%. And the second aging peak is120°C for120h, at this time, the yield stress, peak stress and elongation of this alloy were599MPa,608MPa and12.5%, respectively. Reinforced Al-6Zn-2Mg-2Cu aluminum alloy is mainly the η′(MgZn2)phase. |
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