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Study on Electromagnetic Roll-Casting and Succeed Rolling of AZ61 Magnesium Alloy

Author: LiJinTao
Tutor: XuGuangMing
School: Northeastern University
Course: Materials Processing Engineering
Keywords: AZ61 Mg alloy electromagnetic roll-casting rolling annealing mechanical property microstructure
CLC: TG339
Type: Master's thesis
Year: 2009
Downloads: 43
Quote: 1
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Abstract


Magnesium alloys have been widely used as the light materials in the aerospace, automotive, and electronic industry due to their low density, high specific strength and stiffness, high damping capacity, and good electromagnetic shielding properties. However, the poor plastic deformation capacity of magnesium alloys due to the hexagonal close packed structure with limited slip systems is a major difficulty that must be overcome to enable their widespread application.In this paper, AZ61 strip billet was fabricated by twin-roll casting with electromagnetic field, and the effects of electric and magnetic field on roll-casting microstructure were investigated. Then the twin-roll casting strip billet was rolled into thin strip. Effect of rolling methods on the microstructure and the mechanical properties was studied. A series of results were obtained as follows:(1) The microstructure of magnesium alloys were most composed of equiaxed crystals after common roll-casting, static magnetic roll-casting and electromagnetic roll-casting. The grain size was coarse after common roll-casting. The grains were refined and became equiaxed during static magnetic roll-casting, and the refinement of grain size was the most remarkable during electromagnetic roll-casting;(2) The refinement of grain size was remarkable by water cooling after hot-rolling, but grains would grow abnormally by heating again, which was bad for controlling the microstructure of magnesium alloys by succeed rolling. Therefore, natural cooling should be adapted after hot-rolling;(3) For all rolling technology of magnesium alloys AZ61 studied in this paper, excellent microstructure and mechanical properties were obtained by the following technology:5mm blank→400℃heat preservation 40min→hot-rolling to 2.5mm→natural cooling→400℃heat preservation 10min→ot-rolling to 1.5mm→hot-rolling to 1 mm→water cooling;(4) In the rolling technology of using water cooling after first hot-rolling, The time of annealing at 300℃should not exceed 20min; however annealing time could be extended slightly in the technology of using natural cooling and grains did not grow abnormally;(5) For AZ61 magnesium alloy after electromagnetic roll-casting and succeed rolling:the ductility increased, the strength decreased, and the morphology of tensile fracture tended to be ductile with increasing the annealing time.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metal pressure processing > Rolling > Non-ferrous metal rolling
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