Abstract: The development of lightweight automobile parts for improved fuel efficiency and reduced CO2 emissions often require the use of high strength aluminum alloys. However, high strength aluminum alloys have poor formability because of heterogeneous microstructures and casting defects that are introduced by the addition of solute elements. A homogeneous and refined microstructure is therefore required to improve the extrudability of these alloys. Billet manufactured by the direct chill casting process shows a heterogeneous dendrite microstructure. The production of high quality billet is hindered by segregation and defects such as pores and hot cracks that occur during the casting process. However, the microstructures and intermetallic compounds can be refined and homogenized when the molten aluminum is pulsed. The grain size of the aluminum alloy is greatly refined from 500 to 90 µm when a pulse treatment was applied to an Al-Zn-Mg-Cu alloy melt. The advantages of pulse processing aluminum alloys are increased extrusion speed without cracks and the improvement of high strength aluminum alloy productivity.
Authors: K.H. Kim, M. Slazhniev, S.W. Kim, W.J. Kim, and H.S. Sim
Keywords: High Strength Aluminum Alloys, Microstructure, Pulse Processing Electromagnetic Stirring, Grain Size, Intermetallic Inclusions