Mechanochemical Behavior of NiO-Al-Fe Powder Mixtures to Produce (Ni, Fe) 3 Al-Al 2 O 3 Nanocomposite Powder
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INTRODUCTION
THE Ni3Al intermetallic compound exhibits advantageous properties including high melting temperature, high tensile strength and yield point, low density, high hardness, good thermal stability, high creep resistance, good corrosion, and oxidation resistance at elevated temperatures.[1,2] This is why the intermetallic compound is particularly ideal for many special applications such as cutting tools, coating blades in gas turbines, jet engines, corrosion resistant materials, and heat treatment fixtures. The major barriers for the use of Ni3Al as structural materials are their low toughness and ductility at ambient temperature.[3,4] One practical processing route for direct synthesis of compounds and nanocomposites is mechanical alloying (MA).[5–7] In recent years, there has been increased activity in research on the addition of a third alloying element to different intermetallic compounds. It leads to the improvement of ductility and toughness at ambient temperature.[8–10] Mechanochemical synthesis, in which chemical reactions are induced by mechanical treatment, can raise the mechanical properties.[11–14] Several mechanochemically synthesized nanocomposites such as NiAl-Al2O3,[15] NiTi-Al2O3,[16] Fe3Al-Al2O3,[17] and (Fe, Ti)3AlAl2O3[18] were previously reported. Rafiei et al.[18] studied the formation of (Fe, Ti)3Al-Al2O3 nanocomposites by mechanical alloying of Fe, Al, and TiO2 powder mixture. Consolidation of the ball-milled powders into bulk, full density compacts while retaining nanoscale grain size is a major challenge. Many sintering techniques, e.g., hot pressing, hot extrusion, sintering forging, and HIPing, were employed to consolidate the Z. ADABAVAZEH, MSc Graduate Student, and F. KARIMZADEH and M.H. ENAYATI, Associate Professors and Supervisors, are with the Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran. Contact e-mail: [email protected] Manuscript submitted August 3, 2011. Article published online June 9, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
mechanically alloyed powders. Tavoosi et al.[19] investigated the fabrication of bulk Al-Zn/Al2O3 metal matrix nanocomposites prepared by mechanical alloying and hot pressing. In this work, the aluminum and zinc oxide powder mixture was milled by a planetary ball mill and then hot pressed in a uniaxial die. However, there are few reports in the literature on the MA of ternary Ni-Fe-Al powders. Liu et al. studied the effects of Fe substitution for Al in NiAl alloy. Investigations were performed on the mechanical alloying of Ni50Al50–xFex (x = 5, 10, 15, 20, 25, 30) powders mixture.[20] In our previous work,[21] the formation of (Ni, Fe)3Al intermetallic compound was investigated. In this study, the formation mechanism of the (Ni, Fe)3Al-30 vol pct Al2O3 nanocomposite synthesized by mechanochemical reaction between Al, Fe, and NiO is reported. Finally, the formation mechanism and thermal stability in the milled powder at elevated temperatures was studied by employing X-ray diffractometry
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