| Co-Investigator(Kenkyū-buntansha) |
ZHANG Tao Tohoku University, Institute for Material Research, Research Associate, 金属材料研究所, 助手 (70250818)
KIMURA Hisamichi Tohoku University, Institute for Material Research, Research Associate, 金属材料研究所, 助手 (00161571)
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| Research Abstract |
The main results obtained for the last one year (in 1987) are summarized as follows ; (1) Fe-, Co- and Ni-based bulk amorphous alloys were formed in (Fe, Co, Ni)-(Zr, Hf, Nb, Ta)-B,Fe-(Zr, Nb, Ta)-(Mo, W)-B,Co-Fe-(Zr, Nb, Ta)-B,ni-fe-(zr, nb, Ta)-B systems by various copper mold casting processes and the mechanism for the high glass-forming ability was proposed. (2) these bulk amorphous alloys exhibit a wide supercooled liquid region reaching 89 K in the temperature range below the onset temperature of crystallization (T_x) and the reason for the high thermal stability of the supercooled liquid against crystallization was investigated in the relation to their crystallization behavior. (3) By the use of the high thermal stability of the supercooled liquid, bulk amorphous alloys were formed in the diameter range up to 6 mm by the copper mold casting method. (4) These bulk amorphous alloys exhibit high tensile strength of 2800 to 3200 MPa, high vickers hardness number of 800 to 1100 at ro
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om temperature and high crystallization temperature of 900 to 950 K.(5) An extremely large tensile elongation exceeding 1000 % was obtained in the supercooled liquid region between the glass transition temperature (T_g) and T_x and a linear relation between true stress and true strain was obtained in a wide strain rete range between 10^<-4> and 100S^<-1> and the strain rete sensitivity exponent (m-value) expressed by the slope of the linear relation showed a high value of about 1.0 which can be regarded as an ideal superplastic viscous flowability. besides, the use of the superplastic viscous flowability enabled the working of the bulk amorphous alloys to various complicated outer shapes. Fe-based bulk amorphous alloys exhibited saturated magnetization (B_s) of 0.8 to 1.0 T,low coercivity of 1 to 5 A/m and high permeability of 18000 to 27000 at 1 kHz. Furthermore, the high permability is maintained in the high frequency range as is evidenced from the high value of 8000 at 1 MHz which have not been obtained for any kinds of soft magnetic crystalline alloys. (7) similar high-frequency permeability of about 7000 at 1 MHz was obtained for Co-based bulk amorphous alloys in Co-Fe-Zr-Ta-B system and the excellent high-frequency permeability was presumed to be attributed to the peculiarity of the amorphous structure consisting of the mixture of metal-metal and metal-metalloid types. Less
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