Chuntao Chang

Superhigh strength and good soft-magnetic properties of (Fe,Co)–B–Si–Nb bulk glassy alloys with high glass-forming ability

Fe-based bulk ferromagnetic glassy alloys with diameters up to 5mm were formed in [(Fe1−xCox)0.75B0.2Si0.05]96Nb4 system by the copper mold casting method. The substitution of Co for Fe caused an increase of glass-forming ability as well as an improvement of mechanical and magnetic properties. The bulk glassy alloys exhibited superhigh fracture strength of 3900–4250MPa, Young’s modulus of 190–210GPa, elastic strain of 0.02, and plastic strain of 0.0025. The bulk glassy alloys also exhibited good soft magnetic properties, i.e., saturation magnetization of 0.84–1.13T, low coercive force of 1.5–2.7A∕m, high permeability exceeding 1.2×104, and Curie temperature of 600–690K.

Co–Fe–B–Si–Nb bulk glassy alloys with superhigh strength and extremely low magnetostriction

Co-based bulk glassy alloys with diameters up to 4mm were formed in a [(Co1−xFex)0.75B0.2Si0.05]96Nb4 system. The bulk glassy alloys exhibit a superhigh fracture strength of 3980–4170MPa and Young’s modulus of 190–210GPa. The bulk glassy alloys also exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.71–0.97T, low coercive force of 0.7–1.8A∕m, high permeability of 1.48–3.25×104, and extremely low saturation magnetostriction of 0.55–5.76×10−6. The first successful synthesis of the Co–Fe–B–Si-based bulk glassy alloys exhibiting superhigh fracture strength and excellent soft-magnetic properties with extremely low magnetostriction is encouraging for future development of Co-based bulk glassy alloys as new engineering and functional materials.

FeNi-based bulk glassy alloys with superhigh mechanical strength and excellent soft-magnetic properties

FeNi-based bulk glassy alloys (BGAs) with diameters up to 4mm were formed in [(Fe1−xNix)0.75B0.2Si0.05]96Nb4 system. The increase of Ni to Fe concentration ratio is effective in improving the glass-forming ability. The BGAs exhibit a superhigh fracture strength of 4150–4300MPa, Young’s modulus of 203–215GPa, elastic strain of 0.02, plastic strain of 0.0015, and a well developed vein pattern in the fracture surface. The glassy alloys also exhibit excellent soft-magnetic properties, i.e., rather high saturation magnetization of 0.8–1.1T, low coercive force of 1.2–2.3A∕m, and high permeability of 16 000–24 000 at 1kHz under a field of 1A∕m.

Superhigh strength and excellent soft-magnetic properties of [(Co1−xFex)0.75B0.2Si0.05]96Nb4 bulk glassy alloys

Bulk glassy alloys of [(Co1−xFex)0.75B0.2Si0.05]96Nb4 with diameters up to 4mm were synthesized in the composition range of x=0.1–0.4. In addition to high glass-forming ability, the bulk glassy alloys exhibit superhigh fracture strength of 3980–4170MPa and Young’s modulus of 190–210GPa, as well as excellent soft-magnetic properties, i.e., rather high saturation magnetization of 0.71–0.97T, low coercive force of 0.7–1.8A∕m, high permeability of (1.48–3.25)×104, and extremely low saturation magnetostriction of (0.55–5.76)×10−6. The mechanisms for the high glass-forming ability, superhigh strength, and excellent soft-magnetic properties of the Co-based bulk glassy alloys are discussed.

Enhancement of glass-forming ability of FeCoNiBSiNb bulk glassy alloys with superhigh strength and good soft-magnetic properties

The effect of Zr addition on the glass-forming ability (GFA) of FeCoNiBSiNb glassy alloys in [(Fe0.6Co0.3Ni0.1)0.75B0.2Si0.05]96−xNb4Zrx system was investigated. In addition to slight increases of glass transition temperature from 818to822K and supercooled liquid region from 60to65K, the 1at.% Zr addition was found to be effective in approaching alloy to a eutectic point as well as decreasing liquidus temperature from 1427to1400K, resulting in an increase in GFA. By copper mold casting, [(Fe0.6Co0.3Ni0.1)0.75B0.2Si0.05]95Nb4Zr1 bulk glassy alloys (BGAs) with diameters in the range up to 6mm were produced. The BGA exhibits a superhigh fracture strength of 4180MPa, and Young’s modulus of 200GPa, combined with an elastic strain of 0.02. The glassy alloy exhibits good soft-magnetic properties as well, i.e., rather high saturation magnetization of 1.1T, low coercive force of 2A∕m, and high permeability of 16 700 at 1kHz under a field of 1A∕m. The reason why only 1at.% Zr is effective in improving GFA and the f...

Ni-based bulk glassy alloys with superhigh strength of 3800MPa in Ni–Fe–B–Si–Nb system

The effects of replacement of Ni by Fe on the glass-forming ability (GFA) and mechanical properties of Ni–B–Si–Nb glassy alloys were examined. The substitution of Fe for Ni caused increases of GFA and mechanical properties. Ni-based bulk glassy alloys (BGAs) with diameters up to 3mm were formed in a [(Ni1−xFex)0.75B0.2Si0.05]96Nb4 alloy system. The BGAs exhibit a superhigh fracture strength of 3680–3840MPa and Young’s modulus of 172–186GPa, which are the highest values for Ni-based BGAs. The improvement of GFA and fracture strength is interpreted to result from the enhanced atomic bonding nature among the constituent elements by adding Fe.

Fe-metalloids bulk glassy alloys with high Fe content and high glass-forming ability

The coexistence of high Fe content and high glass-forming ability (GFA) has been earnestly desired from academia to industry. We report a novel Fe 76 Si 9 B 10 P 5 bulk metallic glass with an unusual combination of high magnetization of 1.51 T due to high Fe content as well as high GFA leading to a glassy rod with a diameter of 2.5 mm despite not containing any glass-forming metal elements. This alloy composed of familiar and low-priced elements, also exhibiting very excellent magnetic softness, has a great advantage for engineering and industry, and thus should make a contribution to energy saving and conservation of earth’s resources and environment.

Composition Effect on Intrinsic Plasticity or Brittleness in Metallic Glasses

The high plasticity of metallic glasses is highly desirable for a wide range of novel engineering applications. However, the physical origin of the ductile/brittle behaviour of metallic glasses with various compositions and thermal histories has not been fully clarified. Here we have found that metallic glasses with compositions at or near intermetallic compounds, in contrast to the ones at or near eutectics, are extremely ductile and also insensitive to annealing-induced embrittlement. We have also proposed a close correlation between the element distribution features and the plasticity of metallic glasses by tracing the evolutions of the element distribution rearrangement and the corresponding potential energy change within the sliding shear band. These novel results provide useful and universal guidelines to search for new ductile metallic glasses at or near the intermetallic compound compositions in a number of glass-forming alloy systems.

High-entropy bulk metallic glasses as promising magnetic refrigerants

In this paper, the Ho20Er20Co20Al20RE20 (RE = Gd, Dy, and Tm) high-entropy bulk metallic glasses (HE-BMGs) with good magnetocaloric properties are fabricated successfully. The HE-BMGs exhibit a second-order magnetic phase transition. The peak of magnetic entropy change ( ΔSMpk) and refrigerant capacity (RC) reaches 15.0 J kg−1 K−1 and 627 J kg−1 at 5 T, respectively, which is larger than most rare earth based BMGs. The heterogeneous nature of glasses also contributes to the large ΔSMpk and RC. In addition, the magnetic ordering temperature, ΔSMpk and RC can be widely tuned by alloying different rare earth elements. These results suggest that the HE-BMGs are promising magnetic refrigerant at low temperatures.

Effect of B to si concentration ratio on glass-forming ability and soft-magnetic properties in (Co0.705Fe0.045B0.25-xSix)96Nb4 glassy alloys

The effect of B to Si concentration ratio on the glass-forming ability (GFA) and soft-magnetic properties of (Co0.705Fe0.045B0.25−xSix)96Nb4 (x=0.02–0.1) alloys was investigated. The (Co0.705Fe0.045B0.25−xSix)96Nb4 bulk glassy alloys with diameters up to 2mm were synthesized in the composition range of x=0.02–0.06. In addition to high GFA, the Co-based glassy alloys exhibit excellent soft-magnetic properties as well, i.e., rather high saturation magnetization of 0.62T, low coercive force of 0.6–1A∕m, and superhigh initial permeabilities of 37 100–53 700 at 1kHz under a field of 1A∕m. The alloys with Si contents of x=0.05 and 0.06 exhibit high initial permeabilities of 29 300 and 24 300, respectively, even at 100kHz.