Effect Of Alloying Element Mn On The Microstructures And Properties Of8076Aluminum Alloy For Wire

The8000series of aluminum alloys conducting wires have got more and more attentionsand have been applied widely both at home and abroad, because of its good electricalconductivity, high mechanical strength, outstanding creep resistance, as well as the loweconomic cost. The present work has investigated the microstructures and properties of8076aluminum alloy through elements alloying, drawing and heat treatment, which is aimed todevelop a trace element alloying8076aluminum alloy wire.In order to further reduce the adverse effects of Fe element on alloy mechanical andelectrical properties, Mn element was added into the alloy with various amount in the presentwork. The microstructures evolution and properties changes were investigated through thewhole processing with the Mn addition, drawing and heat treatment. The affection of Mnelement alloying amount, drawing and annealing parameters were also studied. Results showedthat the addition of Mn element has changed the morphology and distribution of Fe phases bothin casting Al alloys and extrusion Al alloys. The original needle, large sheet as well as strip Fephases have been divided into discontinuous fragments with short rod shape, pellets shape,spheres shape, and etc. The electrical conductivity and ductility, as well as the tensile strengthof Al alloy were significantly improved. When the Mn element content is0.05%, the overallperformance of the obtained wire was the best. The researches of the drawing process showedthat: the intermediate passes of annealing between each two single drawing processes, had ledto a better electrical conductivity of the obtained wire than that after drawing withoutintermediate annealing. At Φ3.5mm after350℃intermediate annealing, the optimum overallperformance of final drawing wire is obtained, with electrical conductivity of61.32%IACS,tensile strength of158.3MPa, and elongation of12.16%. Researches on the effect of annealingprocess showed that: the annealing treatment after cold drawing is good to improve the overallperformance of the alloy, and also resolves the conflicts of electrical and mechanical properties.When the annealing temperature was between160℃~400℃, the distorted grains got fullyrecovered and turned into new equiaxed grains after recrystallization. The amount of therecrystallized grains was gradually increased and grew up with the increasing of annealingtemperature, while the conductivity was increased firstly and then decreased. When the annealing temperature is set at330℃, with holding time of1.5h and furnace cooling, theoverall performance of the obtained wire is the best, with conductivity up to61.83%IACS,tensile strength of108.6MPa and elongation of21.86%, which has met with the nationalstandard cables with aluminum conductor wire. In addition, after aging, separated shapes ofhexagonal (Al,Mg) phase and the bulk block of (Al,Mg,Si,Fe) phase had precipitated into thealloy.With different solution temperatures and aging process, the obtained wires performanceswere also different, where the electrical conductivity and elongation have significantlyimproved through a two-stages aging than that through a single-stage aging. When it treatedwith a480℃/1h solid solution through a two-stage aging treatment, the overall performance ofthe wire was the optimum, with the electrical conductivity of60.6%IACS, slightly increased ascompared with that after the cold drawing, and the significantly improved elongation up to20.34%.