Investigation of the Rod Compression Test and Simulation Study of 6061 Aluminum Alloy in the Semisolid State
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THE mushy state in metal can be obtained when a solid metal is heated higher than its solidus line (TS), which means that melting is started and the liquid component appears in its structure. In contrast, the semisolid state in metal occurs when it is cooled to a temperature lower than its liquidus line (TL), meaning that some solidified grains appear in its structure.[1,2] The semisolid state is the case in this study. In the early 1970s, Flemings et al.[3] recommended an innovative casting process called rheocasting. In their method, molten metal is cooled while it is being stirred. During this process, every dendrite growing on a surface is crushed and changed into small particles, and those particles spread in the molten metal. Consequently, the semisolid metal is created. Since the 1970s, a number of experimental investigations into the rheological behavior of materials in the semisolid state have been reported. For example, in 2001, De Freitas and Ferrante[4] dealt with the rheological and deformation characteristics of aluminum alloy 2024 and a laboratory prepared Al-4 pct Cu. In 2002, Kiuchi and Kopp[1] investigated the effect of the semisolid state on production of complicated geometry in comparison with solid state. GHOLAM HOSSEIN ABOUTALEBIAN, Master Student, and PEIMAN MOSADDEGH and MEHRAN MORADI, Assistant Professors, are with the Department of Mechanical Engineering, Isfahan University of Technology, 84156-83111 Isfahan, Iran. Contact e-mail: [email protected] Manuscript submitted September 7, 2013. Article published online April 1, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A
In recent years, semisolid forming has become more popular due to its many advantages such as near net shape, high mechanical properties of final component, and high production efficiency in comparison with traditional processing technologies.[5,6] In 2008, Kim and Kang[7] investigated the effect of the vacuumassisted method on the performance of rheo-forged products and found the optimum fabrication conditions of this method. In 2010, Ju-fu et al.[6] optimized the parameters of the thixoforming process of AZ61 magnesium alloy using numerical simulation and validated the results with experimental data. The semisolid state forming of Al alloys is greatly in demand in automotive and aerospace industries because of its ability to make parts more economical as a result of its low forming temperature in comparison to the casting and low forming forces of forging.[5] To avoid the multiple iteration of making the dies for precise industrial parts, it is necessary to simulate the semisolid forging process in advance; this requires the right model of material at the forming temperature. Ko et al.[8] described the solid phase of semisolid aluminum alloy as a viscoplastic material and used Darcy’s law for the liquid flow. Suyitno et al.[9] numerically simulated the mushy zone behavior of an Al-4.5 pct Cu alloy by considering the viscoplastic material behavior model to express the semisolid state in the finite-element analysis. Zhi-mi
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