Warm Forming of Mg Sheets: From Incremental to Electromagnetic Forming
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MAGNESIUM alloys present high potential for automotive applications due to their lower density in comparison with other widely used structural materials. This property allows not only reducing vehicle weight but also improving dent resistance and structural stiffness by increasing thickness in structural sheet applications.[1] However, as it has been reported by many researchers,[2,3] some limitations emerge when forming magnesium sheet parts. It is well known that due to the strong basal texture of rolled sheets and its hexagonal close-packed (hcp) crystal structure, magnesium alloys present low formability at room temperature due the limited slip and twinning systems available.[4] At room temperature, the predominant slip system in magnesium alloys is slip in the h1120i or hai direction on the basal {0001} plane. Other non-basal slip systems, such as slip of hai on prismatic {1010} planes, hai on pyramidal {1011} planes, and hc + ai on pyramidal {1122} planes, were also observed in magnesium. However, these IBAI ULACIA, Lecturer and Researcher, and IN˜AKI HURTADO, International Relations Coordinator, are with the Mondragon Goi Eskola Politeknikoa, Mondragon Unibersitatea, 20500 Mondrago´n, Spain. Contact e-mail: [email protected] LANDER GALDOS, GURUTZE ARRUEBARRENA, and ENEKO SAENZ DE ARGANDON˜A, Lecturers and Researchers, are with the Advanced Material Forming Processes, Mondragon Goi Eskola Politeknikoa, Mondragon Unibersitatea. JON ANDER ESNAOLA and JON LARRAN˜AGA, Lecturers and Researchers, are with the Structural Mechanics and Design, Mondragon Goi Eskola Politeknikoa, Mondragon Unibersitatea. Manuscript submitted June 30, 2013. Article published online May 14, 2014 3362—VOLUME 45A, JULY 2014
non-basal slip mechanisms are difficult to activate at room temperature due to the higher critical resolved shear stress (CRSS). In addition to dislocation slip, magnesium alloys exhibit strong twinning that may help to satisfy the von Mises criterion at room temperature.[5] Additionally, in magnesium alloys, during deformation at high temperature at quasi-static strain rates, dynamic recrystallization (DRX) is observed. This DRX behavior might improve drastically the deformation of magnesium alloys and it has been extensively studied (e.g.,[6–10]). It has been shown that formability can be improved by increasing the forming temperature, but it is not always achievable in conventional manufacturing processes. Thus, during the last decade, several innovative forming processes with differentiated forming window and application scope have been investigated to manufacture lightweight alloy components. In the current paper, the suitability of innovative forming processes with a wide range of forming rate and application scope to manufacture magnesium sheet parts, such as incremental forming, hydroforming, deep drawing, and electromagnetic forming at warm conditions, is studied to analyze their process window and potential application.
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EXPERIMENTAL PROCEDURES
A. Material The material used in this study was commer
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