Microstructure and Texture Evolution in a Yttrium-Containing ZM31 Alloy: Effect of Pre- and Post-deformation Annealing
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NTRODUCTION
THE increasing demand for an improved fuel economy and for reduced environment-damaging, climatechanging, costly, and human death-causing greenhouse gas emissions in the automotive and aerospace industries has triggered extensive research in the field of lightweight materials.[1,2] It is today even referred to as the ‘‘storm’’ of lightweighting—a revolution in materials, processes, and business models, which is brewing on the horizon of the auto industry.[3] As the lightest structural metallic material, magnesium alloy is one of the most promising candidates to decrease the weight of vehicles.[4] However, its widespread application is still
N. TAHREEN, Ph.D. Student, and D.L. CHEN, Professor and Ryerson Research Chair, are with the Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON M5B 2K3, Canada. Contact e-mail: [email protected] D.F. ZHANG, Professor, is with the College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China, and also with the National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China. F.S. PAN, Professor, is with the College of Materials Science and Engineering, Chongqing University, and also with the National Engineering Research Center for Magnesium Alloys, Chongqing University, and also with the Chongqing Academy of Science and Technology, Chongqing 401123, China. X.Q. JIANG, Professor, is with Advanced Materials Research Center, Chongqing Academy of Science and Technology, and also with Advanced Materials Research Center, the Faculty of Materials and Energy, Southwest University, Chongqing 400715, China. D.Y. LI, Professor, is with the Department of Chemical and Materials Engineering, University of Alberta, Alberta T6G 2V4, Canada. Manuscript submitted September 13, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
limited due to its poor room-temperature ductility or formability, which is mainly caused by the development of a sharp crystallographic texture.[3,5] The presence of a strong basal texture leads to directional anisotropy and extensive twinning during deformation.[6] It is generally recognized that micro-alloying with rare-earth (RE) elements such as yttrium (Y) can retard sharp basal texture formation and thereby improve the formability of magnesium alloy.[7] Thermomechanical processing involving static and dynamic recrystallization is another way to produce new microstructures that could alter the detrimental effect of strong basal texture and, hence, improve the formability of wrought magnesium alloys.[8,9] The process of recrystallization includes the formation of new grains in a plastically deformed material by the formation and migration of high-angle grain boundaries driven by the stored energy of deformation. The recrystallization process tends to soften the material and restore the ductility and formability.[10] As recrystallization needs nucleation sites in the deformed structures, deformation twins could offer the possible sites to form recrystallized gr
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