Three-Ply Al/Mg/Al Clad Sheets Fabricated by Twin-Roll Casting and Post-treatments (Homogenization, Warm Rolling, and An
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ong global warming issues, problems on carbon dioxide emission have received a significant attention in structural material researches, and thus lightweight materials such as Mg and Al alloys have been actively studied.[1–6] Practical uses of Mg alloys have been limited in industrial applications by their poor formability, corrosion resistance, and surface quality, although they have excellent specific strength and damping capacity.[4–9] In order to broaden applications of Mg alloys, various Mg clad sheets covered with Al alloy or stainless steel have been developed by direct solid-state bonding methods.[10,11]
JAEYEONG PARK and HYEJIN SONG, Research Assistants, SEOK SU SOHN, Research Professor, and SUNGHAK LEE, Professor, are with the Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang, 790-784, Korea. Contact e-mail: [email protected] JUNG-SU KIM, Assistant Manager, is with the Technology Appraisal Center, Korea Technology Finance Corporation, Busan, 48400, Korea. Manuscript submitted August 29, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
Considering that most of structural materials are used in a plate or sheet form, twin-roll casting of these lightweight alloys would prove an economic way to reduce manufacturing costs and to expand applicability. It is an environmentally conscious process that can reduce manufacturing costs, labor, and energy since hot-rolling steps are omitted. The twin-roll casting of Mg alloys has also been successfully commercialized.[12–16] When thin Al alloy sheets are clad on to a twin-roll-cast Mg alloy melt by utilizing advantages of twin-roll casting, thus, inherent drawbacks of Mg alloys can be effectively complemented. Bae et al.[17] firstly fabricated Mg clad sheets covered with thin pure Al sheets of 50 lm in thickness using a horizontal twin-roll caster, and found c (Mg17Al12) and b (Mg2Al3) intermetallic compound phases in the Mg/Al reaction zone. This cladding method has been developed further for the fabrication of pilot-plant-scale two-ply Mg/Al sheets by a vertical twin-roll casting route.[18] However, since only one Mg substrate surface is covered with a thin Al sheet in the two-ply Mg/Al clad sheets, three-ply Al/ Mg/Al sheets should be developed for the practical application of clad sheets. In the Al/Mg/Al twin-roll casting process, since a solidified shell of Mg alloy melt is directly contacted with two Al sheets, different approaches and solutions for excellent liquid/solid phase bonding are essentially required. In other words, more studies should be made on details of the liquid/solid phase bonding occurring when both sides of the solidified shell are directly contacted with two thin Al sheets, instead of a roll and an Al sheet. In this study, three-ply Al/Mg/Al clad sheets were fabricated by vertical twin-roll casting and post-treatments including homogenization, warm rolling, and annealing to achieve an economical cladding method. Microstructures of fabricated clad sheets were analyzed, and their tensile properties were expla
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