Effect of Grain Refinement on Tensile Properties of Cast Zinc Alloys
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DUE to the unique combination of properties, i.e., energy-efficient melting, excellent castability, and good corrosion resistance, zinc and its alloys are normally used in the electronic, electrical, and construction industries.[1–4] However, the conventional Zn alloys are not as competitive as cast Al alloys, Mg alloys, or bronze for the structural and pressure-tight components,[5,6] because Zn alloys are prone to low strength and brittle fracture during service, which is associated with the coarse grains in cast Zn alloys.[2,6] It is well recognized that grain refinement can effectively reduce the casting defects, improve homogeneity, and increase mechanical properties in most metallic materials. Therefore, grain refining cast Zn and its alloys is considered as a practical approach to enhance their mechanical properties, widening their applications. Recently, it ZHILIN LIU, Lecturer, is with the College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, P.R. China, and also with the School of Mechanical and Mining Engineering, The University of Queensland, Brisbane, QLD 4072, Australia. DONG QIU, Chancellor Research Fellow, is with the School of Mechanical and Mining Engineering, The University of Queensland, and also with the School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, Melbourne, VIC 3001, Australia. FENG WANG, Postdoctor Research Fellow, is with the School of Mechanical and Mining Engineering, The University of Queensland, and also with the BCAST, Brunel University London, Uxbridge, Middlesex UB8 3PH, U.K. JOHN A. TAYLOR, Associate Professor, and MINGXING ZHANG, Professor, are with the School of Mechanical and Mining Engineering, The University of Queensland. Contact e-mail: [email protected] Manuscript submitted January 7, 2015. Article published online November 18, 2015 830—VOLUME 47A, FEBRUARY 2016
was found that effective grain refinement of cast Zn can be achieved through adding either 0.1 wt pct Mg or 0.5 wt pct Al into cast Zn using master alloys of Zn-60 wt pct Mg and Zn-6 wt pct Al,[7] respectively. However, it was unclear how and to what extent this grain refinement approach can improve the mechanical properties of cast Zn alloys. The actual intrinsic friction of cast pure Zn remains unclear. In addition, because the grain refinement was achieved through addition of solutes, the question is how to distinguish the contribution of grain refinement to yield strength from the contribution of solid solution strengthening. Moreover, the effect of addition of different solutes on the mechanical properties of cast Zn alloys also needs to be clarified. Strengthening mechanisms have been extensively studied in aluminum alloys,[8,9] magnesium alloys,[10–14] and steels.[15] Alloys can be strengthened by single or combined approaches, including grain refinement,[16,17] solid solution,[18,19] precipitation,[14,20] particle dispersion,[21] and strain/work hardening.[22,23] Unfortunately, there are little quantitative data to delineate the contribution
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