Ultrasonic Spot Welding of a Rare-Earth Containing ZEK100 Magnesium Alloy: Effect of Welding Energy
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THE mounting environmental concern to diminish anthropogenic climate-changing, environment-damaging, costly and human death-causing* emissions along *According to Science News entitled ‘‘Air pollution kills 7 million people a year’’ on March 25, 2014 at http://news.sciencemag.org/ signal-noise/2014/03/air-pollution-kills-7-million-people-year: ‘‘Air pollution is not just harming Earth; it’s hurting us, too. Startling new numbers released by the World Health Organization today reveal that one in eight deaths are a result of exposure to air pollution. The data reveal a strong link between the tiny particles that we breathe into our lungs and the illnesses they can lead to, including stroke, heart attack, lung cancer, and chronic obstructive pulmonary disease.’’
with unstable energy prices has driven the transportation industry to improve fuel efficiency.[1–7] Researchers have developed various strategies to improve fuel efficiency including lightweighting, powertrain improvements, aerodynamic (drag reducing) enhancements, and the use of alternative/renewable energy sources. Out of which, lightweighting has been regarded as a key strategy in the global transportation industry.
A. MACWAN, 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] Manuscript submitted July 15, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
Additionally, it has recently been portrayed as the ‘‘storm’’ of lightweighting—a revolution in materials, processes, and business models—which is brewing on the horizon of the transportation industry.[8–11] Magnesium (Mg) alloys are attractive for the transportation industries to achieve vehicle lightweighting due to their low density, high strength-to-weight ratio, and superior damping capacity. Although the wrought (extruded, rolled) Mg alloys show better mechanical properties than the cast counterparts, their applications are limited by the strong deformation texture, which leads to the tension-compression yield asymmetry and mechanical anisotropy.[12,13] This is associated with the hexagonal closed-packed crystal structure of Mg alloys with a nearly ideal c/a ratio (1.624), which results in limited deformation modes (i.e., basal slip and twining) and strong textures at room temperature.[12,14] In addition, Mg alloys also have a poor corrosion resistance compared with Al alloys.[15–17] In recent years, it has been realized that the addition of rare-earth (RE) elements to Mg alloys along with Zn can soften or randomize the texture and improve their room temperature formability.[11,12,18–20] Moreover, it can improve the corrosion resistance of Mg alloys.[21,22] Therefore, some new Mg alloys are being developed by adding RE elements. While Mg alloys with high RE elements, e.g., Mg-10Gd-3Y-0.5Zr,[12,23] or with intermediate RE elements, e.g., Mg-3Nd-0.2Zn-0.5Zr,[24] have been developed for some special applications, more efforts are being mad
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