Effects of Y on the Deformation Mechanisms of Extruded Mg-Y Sheets During Room-Temperature Compression
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TRODUCTION
DUE to their high specific strength and good recycling capacity, use of magnesium (Mg) alloys has made significant progress in lightweight transportation applications such as aerospace, aircraft and high-speed train.[1–4] However, the poor formability and ductility of Mg alloys at room temperature (RT) have hindered their wide use, which originates from the hexagonal close-packed (HCP) crystal structure with limited slip systems.[5] Generally, the mechanical properties of metals are determined by the active deformation modes.[6] Important deformation characteristics, such as yielding, plastic
L.J. LONG, G.H. HUANG, D.D. YIN, and B. JI are with the Key Laboratory for Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, P.R. China. Contact e-mail: [email protected] H. ZHOU is with the Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, P.R. China. D. WANG is with the National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P.R. China. Manuscript submitted October 30, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
anisotropy, work hardening, etc., are governed by the relative contributions of slip and twinning as well as their interactions.[7,8] Thus, detailed and quantitative information about the slip/twinning activity and their dependence on alloying and deformation conditions is critical for understanding the deformation behavior. It is well known that the addition of rare earth (RE) elements to Mg alloy, particularly yttrium (Y), is a good strategy to achieve high ductility and mechanical strength at both room and high temperature as well as creep resistance.[9–18] It is generally accepted that their beneficial influences originate from texture weakening and solid solution strengthening.[19,20] In previous work, we studied the plastic anisotropy,[21] thermal stability and texture evolution[22] of the extruded Mg-Y sheets in detail. These studies showed that Y markedly improved both the strength and ductility of Mg-Y solid solutions even at RT. In addition, nearly isotropic deformation behavior was observed at 300 C tension when the Y content increased to 5 wt pct. Both the fine-grained Mg-1Y and Mg-5Y sheets exhibited significant thermal stability at 300 C annealing. Besides, these extruded Mg-Y sheets exhibited a typical RE texture, and the basal texture was further weakened by annealing. To understand the mechanisms responsible for the improved mechanical properties of Mg-RE alloys, considerable efforts have been made to investigate the
active slip and twinning modes for various conditions. However, there is still some controversy about which deformation modes can be activated and the quantitative contribution of these deformation modes by adding RE elements. For example, some authors[11,23] found enhanced ductility of as-r
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