The Effects Of Preparation Methods And Cooling Rate On The Properties Of Fe-based Amorphous Alloys

As a metastable state, the properties of amorphous alloys are closely related to the preparation history, especially the preparation cooling rate. In this thesis, we examined the influences of the preparation techniques with different cooling rates on glass-forming ability(GFA), thermal property, mechanical property and magnetic property of Fe-based amorphous alloys.(1) We investigated the influences of the preparation techniques with different cooling rates on glass-forming ability(GFA), thermal property and nucleation/growth behavior during solidification of Fe76P5(B0.5Si0.3C0.2)19 bulk glassy alloys. Cylindrical Fe76P5(B0.5Si0.3C0.2)19 rods with diameters of 1 to 2 mm were prepared by J-quenching without flux treatment, Cu-mold injection casting and Cu-mold suction casting. The maximum diameter for the formation of Fe76P5(B0.5Si0.3C0.2)19 glassy alloy prepared by J-quenching, Suction casting, and Injection casting were 1.7 mm, 1mm and less than1 mm, respectively. The microstructure of the partially crystallized rods in as-prepared state is quite different between the injection cast and the J-quenched rods. It is presumed that such a significant difference is attributed to the change in the nucleation and growth mode for the J-quenching and the injecting casting processes.(2) Bulk Fe80-xCoxP13C7(x = 0, 5, 10, 15, 20 at.%) glassy alloy rod/ribbon have been successfully prepared by a combination method of fluxing technique and J-quenching / melt-spinning techniques in this study. And we studied the influences of the preparation cooling rates on thermal property, mechanical property and magnetic property of Fe80-x CoxP13C7 amorphous alloys. It reveals that the the saturation magnetization(Ms) of Fe80-xCoxP13C7(x = 0, 5, 10, 15, 20 at.%) ribbons and BMGs exhibit different change rules with the addition of Co content. The Ms of the present FeCoPC ribbons monotonously decreases upon Co addition, while the Ms of the BMGs initially increases up to the maximum value of 165 emu/g for x = 5 and then deceases with the substitution amount of Co for Fe. The magnetic domain structuresbetween the amorphous ribbon and bulk amorphous alloy are quite different. The band domains with a width of ~5 μm are observed in the free surface of the amorphous ribbon while the domains in the longitude section of the bulk amorphous alloys show a branched morphology with a narrow width and high density.