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The hardness, conductivity and room temperature tensile test were used to study the properties of the new aluminum alloy aged at 110-140 ℃ for different time.The microstructure of the alloy was observed by transmission microscope (TEM).The results show that the optimum aging process of the new aluminum alloy is aging at 110 ℃ for 24 h.Tensile strength, yield strength and elongation are 808,785 MPa,6.9%, respectively.Aging temperature is the main factor affecting the type, density and size of precipitates.When aged at 110 ℃,the main precipitations are GPⅠ zones,GPⅡ zones and metastable η' phase. After aging at 110 ℃ for a long time (up to 96 h), GPⅠ zones and GPⅡ zones still exist stably.Compared with aging at 110 ℃, the precipitation process accelerates at 140 ℃.After aging at 140 ℃ for 4 h, no GP zone is observed, and the main precipitate phase is η'.After aging at 140 ℃ for 24 h, the main precipitates are η' phase and η phase.

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The main advantage of High Strength Steel (HSS) is to decrease material thickness at the same performance level and to increase the performance level with unchanged dimensions. The demand of HSS is getting increasing to satisfy the increasing technical requirements as well as the needs for good handling during constructions as building height and span is getting taller and longer. New 800 MPa high (tensile) strength steel plate for building structures, namely HSA800, was developed in 2011. As made by TMCP, it has a good weldability without increasing carbon contents. Material performance tests of HSA800 for 10-100 mm thick plates are conducted to verify if satisfying the Korean Industrial Standard (KS) provisions. Then applicability of HSA800 in a super-tall building is evaluated by creating two analytical models (with or without HSA800) for comparison in accordance with five performance index - lateral deflection, column shortening, natural periods, overturning moments and total amounts of materials. In this case, HSA800 is applied to gravity members such as perimeter columns, spandrel beams and belt trusses rather than lateral force resisting members to keep the building lateral stiffness. Material test results show that HSA800 satisfies all chemical and mechanical KS provisions and can be used to design structures per current design codes. The behavior of the model using HSA800 was similar to that of normal strength steel (SM570) only model and satisfied all five performance index. Saving amounts of steel quantity by using HSA800 were approximately 4500 tons, which is 30% of total gravity member amounts and 10% of total steel amounts used in this model. Consequently, use of HSS, such as HSA800, may bring the added benefit of reducing steel consumption compared to normal strength steels and decreasing carbon dioxide (CO) emissions from steel and member production processes. [ABSTRACT FROM AUTHOR]