Macro- and Microstructural Studies of Laser-Processed WE43 (Mg-Y-Nd) Magnesium Alloy
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ODUCTION
DOWNSIZING vehicle weight, fuel economy, overall production cost, product reliability, market sustainability, and service durability are among the key benchmarks of the transportation industry. Toward that end, Mg alloys are widely acknowledged as suitable candidates to serve the purposes of transportation industry. Mg is 36.8 and 78.2 pct lighter per unit volume than aluminum and iron, respectively; and possesses good physical, chemical, and mechanical properties useful for various applications.[1] Various Mg alloys such as AZ (Mg-Al-Zn), AM (Mg-Al-Mn), AS (Mg-Al-Si), AE (Mg-Al-RE), and WE (Mg-Y-RE) have been designed, developed, and successfully used according to specific applications.[1] However, properties such as low fatigue, as well as creep properties, and poor resistance to corrosion and wear have limited their structural applications. The macroscopic mechanical properties of the Mg alloys are the manifestations of the micromechanics of interaction between dislocations and many other microstructural elements present in a metallic material.
S. SANTHANAKRISHNAN, formerly with Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, is now Assistant Professor at the Manufacturing Division, Mechanical Engineering Department, Indian Institute of Technology-Madras, Chennai 600 036, India. N. KUMAR and D. CHOUDHURI, Post-Doctoral Associates, N. DENDGE, S. KATAKAM, S. PALANIVEL, and H.D. VORA, Doctoral Students, R. BANERJEE and R.S. MISHRA, Professors, and NARENDRA B. DAHOTRE, Professor and Chairman, are with the Department of Materials Science and Engineering, University of North Texas. Contact e-mail: [email protected] Manuscript submitted February 26, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
Precipitation strengthening is a widely recognized means of improving the strength of many commercially available alloys. Temperature-dependent kinetics are crucial in governing the competing aspects (diffusional and thermodynamic) of each element in Mg alloys. In light of this, a precisely controlled, high-power laser can be used to tailor the surface and the corresponding mechanical properties of Mg alloys. Laser processing (LP) generates localized rapid heating followed by rapid cooling concurrently, which in turn results in rapid melting and solidification. In this process, the localized laser–material interaction for short duration (ls to ms) produces conditions far beyond the thermodynamic equilibrium state, thereby resulting in unique surface and mechanical properties. Hence, judicious selection of alloying elements (chemistry and composition), processing technique(s), and processing parameters may be key to optimization of mechanical properties through the introduction of important microstructural components.
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BACKGROUND
To enhance the mechanical and surface properties of Mg, elements such as aluminum (Al), Zirconium (Zr), rare earth (RE) elements (scandium (Sc), neodymium (Nd), yttrium (Y), cerium (Ce)), Manganese (Mn), Silicon (Si), and Zinc (Zn) are
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