Ni-Nb-Sn Bulk Metallic Glass Matrix Composites Fabricated by Microwave-Induced Sintering Process
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THE microwave (MW)–induced sintering process has attracted increasing attention due to its significant advantages in material processing compared to conventional processes. The MW radiation causes internal heating of the materials, and it is a volumetric heating involving conversion of electromagnetic energy into thermal energy, which is instantaneous, rapid, and efficient,[1,2] so that a lower temperature and shorter time can be used compared to those applied at conventional heating processes. The MW processing can reduce sintering time by a factor of 10 in some cases and minimize grain growth. In materials science, the MW-induced sintering process was traditionally applied to ceramics. It was demonstrated that MW energy could be used for processing full-scale ceramic products.[3,4] However, applicability of microwave sintering to metals was ignored due to the fact that they reflect microwaves. Roy et al. reported that powdered metals could be heated rapidly in microwaves and fully sintered samples were obtained in a multimode cavity.[5,6] Subsequently, microwave heating of the powdered metals in separated magnetic (H) field and electric (E) field was performed in a single-mode applicator.[7,8] The microwave sintering of various metallic powders, steels, and nonferrous alloys GUOQIANG XIE, Assistant Professor, Institute for Materials Research, SONG LI, Researcher, and D.V. LOUZGUINE-LUZGIN, Professor, WPI Advanced Institute for Materials Research, ZIPING CAO, Researcher, and NOBORU YOSHIKAWA, Associate Professor, Graduate School of Environmental Studies, and AKIHISA INOUE, Professor, are with Tohoku University, Sendai 980-8577, Japan. Contact e-mail: [email protected] MOTOYASU SATO, Professor, is with the National Institute for Fusion Science, Toki 5095292, Japan. This article is based on a presentation given in the symposium ‘‘Bulk Metallic Glasses VI,’’ which occurred during the TMS Annual Meeting, February 15–19, 2009, in San Francisco, CA, under the auspices of TMS, the TMS Structural Materials Division, TMS/ASM: Mechanical Behavior of Materials Committee. Article published online November 12, 2009 1714—VOLUME 41A, JULY 2010
produced sintered samples within tens of minutes at sintering temperatures between 1370 and 1570 K.[9–12] Moreover, nanomaterials and some composite materials were produced by the MW sintering technique.[13–18] The Ni-based bulk metallic glasses (BMGs) exhibit high thermal stability, ultrahigh strength, and excellent corrosion resistance.[19] Recently, Ni-based BMG rods with diameters up to 2 to 5 mm in various Ni-based metal-metal alloy systems were produced using a Cu mold casting technique;[20–23] those with a diameter of 15 mm in the metal-metalloid Ni-Pd-P-B alloy system were prepared by a water quenching technique along with flux treatment.[24] However, the critical diameter of Ni-based BMGs obtained is much smaller compared to Zr-, Pd-, and Cu-based BMGs with critical diameters of over 20 mm. This limits the extensive practical applications of Ni-based BMGs. The powder metal
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