Structure and Soft Magnetic Properties of Bulk Fe-Al-Ga-P-C-B-Si Glassy Alloys Prepared by Consolidating Glassy Powders
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Structure and Soft Magnetic Properties of Bulk Fe-Al-Ga-P-C-B-Si Glassy Alloys Prepared by Consolidating Glassy Powders Akihisa Inoue1, Shoji Yoshida, Takao Mizushima and Akihiro Makino Magnetic Devices Division, ALPS Electric Corporation, Ltd., 1-3-5, Higashitakami, Nagaoka-City, Niigata-Pref., 940-8572 1 Institute for Materials Research, Tohoku University, 2-1-1, Katahira, Aoba-ku, Sendai-City, Miyagi-Pref., 980-8577 ABSTRACT With the aim of developing a bulk glassy Fe-based alloy with good soft magnetic properties by the powder metallurgy technique, we have applied the pulse current sintering technique to a Fe70Al5Ga2P9.65C5.75B4.6Si3 glassy alloy powder with a large supercooled liquid region of 60K before crystallization. The existence of the supercooled liquid region was found to enable us to form a bulk glassy alloy with a very high relative density of 99%. The resulting bulk glassy alloy exhibits good soft magnetic properties, i.e., 1.17T for flux density at a field of 800A/m, 12.0A/m for coercive force and 8000 for maximum permeability which are much superior to those for the bulk amorphous Fe-Si-B alloy prepared by the same sintering method. The much better soft magnetic properties for the multicomponent Fe-based bulk alloy are attributed to the combination of the high relative density and the unique amorphous structure with the features of high packing density and long-range homogeneous atomic configurations. The first success of forming the bulk amorphous alloy with good soft magnetic properties by the powder metallurgy technique is expected to enable us to use as practical soft magnetic materials. INTRODUCTION Since amorphous alloys in Fe-metalloid systems were found to exhibit good soft magnetic properties because of the absence of crystal magnetic anisotropy and grain boundaries in 1974 [1-3], a large number of studies on the development of soft magnetic amorphous alloys have been carried out for the subsequent ten years. It is well known that Fe-Si-B and Co-Fe-Si-B base amorphous alloys have been used as practical soft magnetic materials of high saturated magnetization-type and high-permeability-type, respectively [4]. However, the shape and dimension of the soft magnetic alloys have been limited to thin sheet with a thickness less than about 50µm and fine wire with a diameter less than 150µm, because of the necessity of high cooling rates for formation of an amorphous phase [5, 6]. It is strongly expected that the elimination of the limitation of the sample shape and dimension causes a more wide extension of application fields. Since 1995, some new types of Fe-based amorphous alloys with high glass-forming ability have been found in Fe-(Al, Ga)-(P, C, B) [7], Fe-(Nb, Cr, Mo)-(Al, Ga)-(P, C, B) [8], Fe-Ga-(P, C, B) [9], Fe-(Nb, Cr, Mo)-Ga-(P, C, B) [10, 11], Fe-(Zr, Hf, Nb)-B [12], Fe-(Zr, Nb, Ta)-(Cr, Mo, W)-B [13] and Fe-(Cr, Mo)-(B, C) [14] systems. The use of these new Fe-based alloy compositions has enabled us to produce bulk amorphous alloys with a thickness up to 3mm for the Fe-(Al, Ga)-(P, C,
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