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William L. Johnson - One of the best experts on this subject based on the ideXlab platform.

  • Extremely low Critical Cooling Rate measured on dispersed Pd43Ni10Cu27P20
    Applied Physics Letters, 2002
    Co-Authors: Jan Schroers, William L. Johnson
    Abstract:

    Crystallization of dispersed Pd43Ni10Cu27P20 melts is studied during constant Cooling and heating. Investigations are carried out on samples that are dispersed into several hundred particles which are fluxed in B2O3. The size of the particles is chosen in such a way that crystallization of individual particles can be observed. Constant Cooling experiments with Rates between 0.3 and 0.0016 K/s are performed. In order to determine the fraction of particles that crystallize upon Cooling, the crystallization during subsequent heating at 0.3 K/s is utilized. 10%–15% of the particles do not crystallize during Cooling with a Rate as low as 0.005 K/s. This is the lowest Rate that avoids crystallization ever measured for a metallic system. This extremely low Critical Cooling Rate suggests that a fraction of the particles do not contain the impurities that act as nuclei in bulk samples. Therefore, in these particles, nuclei first have to form and crystallization does not take place, as it was found for bulk Pd43Ni10Cu27P20, by the growth on pre-existing nuclei formed by impurities.

  • Critical Cooling Rate and thermal stability of Zr–Ti–Cu–Ni–Be alloys
    Applied Physics Letters, 2001
    Co-Authors: Theodore A. Waniuk, Jan Schroers, William L. Johnson
    Abstract:

    The Critical Cooling Rate as well as the thermal stability are measured for a series of alloys in the Zr–Ti–Cu–Ni–Be system. Upon Cooling from the molten state with different Rates, alloys with compositions ranging along a tie line from (Zr70Ti30)55(Ni39Cu61)25Be20 to (Zr85Ti15)55(Ni57Cu43)22.5Be27.5 show a continuous increase in the Critical Cooling Rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for some compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the composition-dependent glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

  • Critical Cooling Rate and Thermal Stability in Zr-Ti-Cu-Ni-Be Bulk Metallic Glasses
    MRS Proceedings, 2000
    Co-Authors: Theodore A. Waniuk, Jan Schroers, William L. Johnson
    Abstract:

    The crystallization behavior of a series of alloys in the Zr-Ti-Cu-Ni-Be system is studied. Upon Cooling from the molten state with different Rates, alloys with compositions ranging along a tie line from (Zr75Ti25)55(Ni45Cu55)22.5Be22.5 (Vit1) to (Zr85Ti15)55(Ni57Cu43)17.5Be27.5 (Vit4) show a continuous increase in the Critical Cooling Rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the change in glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

Akihisa Inoue - One of the best experts on this subject based on the ideXlab platform.

  • pd30pt17 5cu32 5p20 alloy with low Critical Cooling Rate of 0 067k s
    Applied Physics Letters, 2006
    Co-Authors: N. Nishiyama, K. Takenaka, Akihisa Inoue
    Abstract:

    In order to realize biomedical applications of bulk glassy alloys, Pd-based glassy alloys with Ni-free composition were developed. The alloy with the highest glass-forming ability was obtained at a composition of Pd30Pt17.5Cu32.5P20. The Critical Cooling Rate for glass formation was measured to be 0.050–0.067K∕s. It is also recognized that the crystallization of the undercooled alloy is mainly dominated by surface nucleation. The apparent crystal growth Rate of the alloy was slightly higher than that of the previously reported Pd40Cu30Ni10P20 alloy at the same degree of underCooling. The highly processable feature of the alloy has potential for biomedical applications.

  • Pd30Pt17.5Cu32.5P20 alloy with low Critical Cooling Rate of 0.067K∕s
    Applied Physics Letters, 2006
    Co-Authors: N. Nishiyama, K. Takenaka, Akihisa Inoue
    Abstract:

    In order to realize biomedical applications of bulk glassy alloys, Pd-based glassy alloys with Ni-free composition were developed. The alloy with the highest glass-forming ability was obtained at a composition of Pd30Pt17.5Cu32.5P20. The Critical Cooling Rate for glass formation was measured to be 0.050–0.067K∕s. It is also recognized that the crystallization of the undercooled alloy is mainly dominated by surface nucleation. The apparent crystal growth Rate of the alloy was slightly higher than that of the previously reported Pd40Cu30Ni10P20 alloy at the same degree of underCooling. The highly processable feature of the alloy has potential for biomedical applications.

  • UnderCooling Behavior and Critical Cooling Rate of Pd-Pt-Cu-P Alloy
    MATERIALS TRANSACTIONS, 2005
    Co-Authors: Nobuyuki Nishiyama, K. Takenaka, Takeshi Wada, Hisamichi Kimura, Akihisa Inoue
    Abstract:

    In order to realize biomedical applications of bulk glassy alloys, we have developed new Pd-based glassy alloys with Ni-free composition in Pd-Pt-Cu-P system and it is revealed that the highest glass-forming ability is obtained at a composition of Pd 35 Pt 15 Cu 30 P 20 . In addition the alloy can be formed into bulk glassy rods with diameters of up to at least 30 mm by fluxed water quenching. In order to clarify the Critical Cooling Rate for glass-formation, underCooling behavior and crystal growth Rate are also discussed. Crystallization of the alloy under continuous Cooling is mainly dominated by surface nucleation. Apparent crystal growth Rate of the alloy at 0.73 T m is evaluated to be 5.2 x 10 -6 m·s -1 and this value is four orders of magnitude higher than that of previous Pd 40 Cu 30 Ni 10 P 20 at the same degree of underCooling.

  • stability and nucleation behavior of glass forming pd cu ni p alloy with a Critical Cooling Rate of 0 067 k s
    Intermetallics, 2002
    Co-Authors: Nobuyuki Nishiyama, Akihisa Inoue
    Abstract:

    Abstract An undercooled Pd 42.5 Cu 30 Ni 7.5 P 20 melt having a eutectic composition exhibits the lowest Critical Cooling Rate for glass formation of 0.067 K/s. Nucleation and crystal growth behaviors of the undercooled melt were investigated. For example, nucleation frequency and crystal growth Rate at 683 K where the temperature is close to nose temperature were evaluated as 4.76×10 9 nuclei/m 3 s and 3.24×10 −7 m/s, respectively. These values are almost the same as those for the undercooled Pd 40 Cu 30 Ni 10 P 20 melt which has a slightly off-eutectic composition. However, the difference in incubation time for crystallization and nucleation mode was observed in both melts. The nucleation mechanism of undercooled Pd 42.5 Cu 30 Ni 7.5 P 20 and Pd 40 Cu 30 Ni 10 P 20 melt is compared. Based on these results, the prolongation in incubation time for crystallization is discussed in the present study.

  • Direct comparison between Critical Cooling Rate and some quantitative parameters for evaluation of glass-forming ability in Pd-Cu-Ni-P alloys : Bulk amorphous, nano-crystalline and nano-quasicrystalline alloys IV
    Materials Transactions Jim, 2002
    Co-Authors: Nobuyuki Nishiyama, Akihisa Inoue
    Abstract:

    The quantitative parameters such as supercooled liquid region or several reduced glass transition temperatures were applied for evaluating the glass-forming ability of Pd-based metallic glasses. A distinct proportional tendency was recognized between measured Critical Cooling Rates and reduced glass transition temperature by liquidus temperature rather than eutectic temperature. Significance and physical meanings of the quantitative parameters for evaluating of glass-forming ability were also discussed. Furthermore, a new concept of a modified reduced glass transition temperature was proposed to evaluate the glass-forming ability. The modified reduced glass transition temperature as a function of Critical Cooling Rate was found to exhibit a much clear linearity.

Jan Schroers - One of the best experts on this subject based on the ideXlab platform.

  • Extremely low Critical Cooling Rate measured on dispersed Pd43Ni10Cu27P20
    Applied Physics Letters, 2002
    Co-Authors: Jan Schroers, William L. Johnson
    Abstract:

    Crystallization of dispersed Pd43Ni10Cu27P20 melts is studied during constant Cooling and heating. Investigations are carried out on samples that are dispersed into several hundred particles which are fluxed in B2O3. The size of the particles is chosen in such a way that crystallization of individual particles can be observed. Constant Cooling experiments with Rates between 0.3 and 0.0016 K/s are performed. In order to determine the fraction of particles that crystallize upon Cooling, the crystallization during subsequent heating at 0.3 K/s is utilized. 10%–15% of the particles do not crystallize during Cooling with a Rate as low as 0.005 K/s. This is the lowest Rate that avoids crystallization ever measured for a metallic system. This extremely low Critical Cooling Rate suggests that a fraction of the particles do not contain the impurities that act as nuclei in bulk samples. Therefore, in these particles, nuclei first have to form and crystallization does not take place, as it was found for bulk Pd43Ni10Cu27P20, by the growth on pre-existing nuclei formed by impurities.

  • Critical Cooling Rate and thermal stability of Zr–Ti–Cu–Ni–Be alloys
    Applied Physics Letters, 2001
    Co-Authors: Theodore A. Waniuk, Jan Schroers, William L. Johnson
    Abstract:

    The Critical Cooling Rate as well as the thermal stability are measured for a series of alloys in the Zr–Ti–Cu–Ni–Be system. Upon Cooling from the molten state with different Rates, alloys with compositions ranging along a tie line from (Zr70Ti30)55(Ni39Cu61)25Be20 to (Zr85Ti15)55(Ni57Cu43)22.5Be27.5 show a continuous increase in the Critical Cooling Rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for some compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the composition-dependent glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

  • Critical Cooling Rate and Thermal Stability in Zr-Ti-Cu-Ni-Be Bulk Metallic Glasses
    MRS Proceedings, 2000
    Co-Authors: Theodore A. Waniuk, Jan Schroers, William L. Johnson
    Abstract:

    The crystallization behavior of a series of alloys in the Zr-Ti-Cu-Ni-Be system is studied. Upon Cooling from the molten state with different Rates, alloys with compositions ranging along a tie line from (Zr75Ti25)55(Ni45Cu55)22.5Be22.5 (Vit1) to (Zr85Ti15)55(Ni57Cu43)17.5Be27.5 (Vit4) show a continuous increase in the Critical Cooling Rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the change in glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

Theodore A. Waniuk - One of the best experts on this subject based on the ideXlab platform.

  • Critical Cooling Rate and thermal stability of Zr–Ti–Cu–Ni–Be alloys
    Applied Physics Letters, 2001
    Co-Authors: Theodore A. Waniuk, Jan Schroers, William L. Johnson
    Abstract:

    The Critical Cooling Rate as well as the thermal stability are measured for a series of alloys in the Zr–Ti–Cu–Ni–Be system. Upon Cooling from the molten state with different Rates, alloys with compositions ranging along a tie line from (Zr70Ti30)55(Ni39Cu61)25Be20 to (Zr85Ti15)55(Ni57Cu43)22.5Be27.5 show a continuous increase in the Critical Cooling Rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for some compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the composition-dependent glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

  • Critical Cooling Rate and Thermal Stability in Zr-Ti-Cu-Ni-Be Bulk Metallic Glasses
    MRS Proceedings, 2000
    Co-Authors: Theodore A. Waniuk, Jan Schroers, William L. Johnson
    Abstract:

    The crystallization behavior of a series of alloys in the Zr-Ti-Cu-Ni-Be system is studied. Upon Cooling from the molten state with different Rates, alloys with compositions ranging along a tie line from (Zr75Ti25)55(Ni45Cu55)22.5Be22.5 (Vit1) to (Zr85Ti15)55(Ni57Cu43)17.5Be27.5 (Vit4) show a continuous increase in the Critical Cooling Rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the change in glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

Mo Li - One of the best experts on this subject based on the ideXlab platform.

  • atomic size effect on Critical Cooling Rate and glass formation
    Physical Review B, 2005
    Co-Authors: Payman Jalali, Mo Li
    Abstract:

    Atomic size effect on Critical Cooling Rate and glass formability in a model binary system is investigated using molecular dynamics simulation. To isolate atomic size effect from the rest of the factors that Critically influence the glass formation, a hard sphere model is employed in conjunction with a newly developed densification method. The glass formability is defined as a set of optimal conditions that result in the slowest Cooling Rate of the glass-forming liquid. Critical Cooling Rates are identified from extensive molecular dynamics simulations. A kinetic glass-forming diagram is mapped out that marks the boundary between the glass-forming regions and competing crystalline phases in terms of the parameters of the atomic size ratio and alloy concentration. It is found that the potency of the atomic size difference on glass formation is influenced greatly by the competing metastable and equilibrium crystalline phases in the system, and the kinetic processes leading to the formation of these phases. The mechanisms of the atomic size effect on topological instability of crystal packing and glass formation are discussed.