The present work found the plastic deformability of Zr65Cu17.5Ni10Al7.5 BMG dependent on the cooling rate during the formation from the molten state alloy. The deformation behavior in the compression test of φ 2 mm Z...The present work found the plastic deformability of Zr65Cu17.5Ni10Al7.5 BMG dependent on the cooling rate during the formation from the molten state alloy. The deformation behavior in the compression test of φ 2 mm Zr65Cu17.5Ni10Al7.5 BMGs as-cast or lathed from different sizes as-cast samples was characterized, and they exhibited different plastic strains. The compressive plastic strain increases with the decreasing diameter of the as-cast specimens, i.e. with increasing the cooling rate. It is suggested that free volume content in the BMGs, which is related to the cooling rate during the rapid solidification, could play an important role in the deformation process of the BMGs.展开更多
The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabr...The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-A1-Cu-Co alloys was well-correlated with the supercooled liq- uid region, ATx, and the parameter, 7; but not with the reduced glass transition temperature, Trg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be used in various applications. The GFA of the pre- sent alloys exhibited a dependence on the relative number of AlqEo and AI-Cu atomic pairs, i.e., on the AI：Co and AI：Cu ratios, which were -2.3 and 0.85, respectively.展开更多
Co48-xFexCr15Mo14C15B6Er2 (x = 2.5 and 5) bulk metallic glasses (BMGs) with critical size (dc) up to 15 mm in diameter were synthesized by copper mold casting. Co43Fe5Cr15Mo14C15B6Er2 BMG has a wide supercooled liquid...Co48-xFexCr15Mo14C15B6Er2 (x = 2.5 and 5) bulk metallic glasses (BMGs) with critical size (dc) up to 15 mm in diameter were synthesized by copper mold casting. Co43Fe5Cr15Mo14C15B6Er2 BMG has a wide supercooled liquid region (84 K) and ultrahigh fracture strength exceeding 5000 MPa,which is the highest value for reported metallic glasses with dc exceeding 1 cm. Furthermore,the Poisson ratio,Young modulus,shear modulus and bulk modulus of this alloy were evaluated to be 0.31,217 GPa,82 GPa and 214 GPa,respectively. The ideal configurational entropy of Co48-xFexCr15Mo14C15B6Er2 (x = 0 and 5) has been calculated. The introduction of the similar element Fe in the Fe-free Co-Cr-Mo-C-B-Er alloy will be beneficial to increasing the ideal config-urational entropy and depressing the critical cooling rate to achieve greater glass-forming ability. The combination of superior glass-forming ability and ultrahigh fracture strength makes the present Co48-xFexCr15Mo14C15B6Er2 (x = 2.5 and 5) BMGs promising candidates as advanced structural materials.展开更多
The Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current, and then by isothermal anne...The Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current, and then by isothermal annealing at near initial crystallization temperature for different periods of time. The precipitations and crystallization fractions were studied by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), and their effects on mechanical properties of the composite were studied by microhardness, uniaxial compression test and scanning electron microscopy (SEM). The experimental results show that the primary precipitate is quasicrystalline phase and other metastable phases including Be2Zr, Zr2Cu and FCC would precipitate subsequently. In the initial crystallization process, in which the crystallization fraction increases from 0 to 8.2%, both fracture strength and plastic strain increase, with the maximum plastic strain up to 6.4%. When the crystallization fraction is larger than 8.2%, the fracture strength and the plastic strain decrease sharply. Furthermore, the alloy with low crystallization fraction is fractured by shearing, while for high crystallization fraction it is fractured by splitting and cleavage. The results show that the mechanical properties of the glassy alloy could be optimized by controlling the processing parameters.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 50771006 and 50631010)the National Basic Research Program of China (Grant No. 2007CB613900)+1 种基金PCSIRT (Grant No. IRT0512)NCET (Grant No. NCET-07-0041)
文摘The present work found the plastic deformability of Zr65Cu17.5Ni10Al7.5 BMG dependent on the cooling rate during the formation from the molten state alloy. The deformation behavior in the compression test of φ 2 mm Zr65Cu17.5Ni10Al7.5 BMGs as-cast or lathed from different sizes as-cast samples was characterized, and they exhibited different plastic strains. The compressive plastic strain increases with the decreasing diameter of the as-cast specimens, i.e. with increasing the cooling rate. It is suggested that free volume content in the BMGs, which is related to the cooling rate during the rapid solidification, could play an important role in the deformation process of the BMGs.
文摘The glass forming ability （GFA） and thermodynamic properties of the La-AI-Cu-Co alloy system were investigated, and novel La-AI-Cu-Co bulk metallic glasses （BMGs） with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-A1-Cu-Co alloys was well-correlated with the supercooled liq- uid region, ATx, and the parameter, 7; but not with the reduced glass transition temperature, Trg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be used in various applications. The GFA of the pre- sent alloys exhibited a dependence on the relative number of AlqEo and AI-Cu atomic pairs, i.e., on the AI：Co and AI：Cu ratios, which were -2.3 and 0.85, respectively.
基金supported by the National Basic Research Program of China (2007CB613900)the National Natural Science Foundation of China (51071008)
文摘Co48-xFexCr15Mo14C15B6Er2 (x = 2.5 and 5) bulk metallic glasses (BMGs) with critical size (dc) up to 15 mm in diameter were synthesized by copper mold casting. Co43Fe5Cr15Mo14C15B6Er2 BMG has a wide supercooled liquid region (84 K) and ultrahigh fracture strength exceeding 5000 MPa,which is the highest value for reported metallic glasses with dc exceeding 1 cm. Furthermore,the Poisson ratio,Young modulus,shear modulus and bulk modulus of this alloy were evaluated to be 0.31,217 GPa,82 GPa and 214 GPa,respectively. The ideal configurational entropy of Co48-xFexCr15Mo14C15B6Er2 (x = 0 and 5) has been calculated. The introduction of the similar element Fe in the Fe-free Co-Cr-Mo-C-B-Er alloy will be beneficial to increasing the ideal config-urational entropy and depressing the critical cooling rate to achieve greater glass-forming ability. The combination of superior glass-forming ability and ultrahigh fracture strength makes the present Co48-xFexCr15Mo14C15B6Er2 (x = 2.5 and 5) BMGs promising candidates as advanced structural materials.
基金supported by the National Basic Research Program of China (Grant No. 2007CB613905)the National Natural Science Foundation of China (Grant Nos. 50671050 and 50971073)
文摘The Zr41Ti14Cu12.5Ni10Be22.5 (at.%) bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current, and then by isothermal annealing at near initial crystallization temperature for different periods of time. The precipitations and crystallization fractions were studied by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), and their effects on mechanical properties of the composite were studied by microhardness, uniaxial compression test and scanning electron microscopy (SEM). The experimental results show that the primary precipitate is quasicrystalline phase and other metastable phases including Be2Zr, Zr2Cu and FCC would precipitate subsequently. In the initial crystallization process, in which the crystallization fraction increases from 0 to 8.2%, both fracture strength and plastic strain increase, with the maximum plastic strain up to 6.4%. When the crystallization fraction is larger than 8.2%, the fracture strength and the plastic strain decrease sharply. Furthermore, the alloy with low crystallization fraction is fractured by shearing, while for high crystallization fraction it is fractured by splitting and cleavage. The results show that the mechanical properties of the glassy alloy could be optimized by controlling the processing parameters.
