Characteristic free volumes of bulk metallic glasses: Measurement and their correlation with glass-forming ability

Abstract

Construction of a disorder variable from Steinhardt order parameters in binary mixtures at high densities in three dimensions J. Chem. Phys. 135, 174109 (2011) Fragility of iron-based glasses Appl. Phys. Lett. 99, 161902 (2011) Communication: Are metallic glasses different from other glasses? A closer look at their high frequency dynamics J. Chem. Phys. 135, 101101 (2011) Temperature dependence of the thermoplastic formability in bulk metallic glasses J. Appl. Phys. 110, 043518 (2011) The electronic structure origin for ultrahigh glass-forming ability of the FeCoCrMoCBY alloy system J. Appl. Phys. 110, 033720 (2011) Additional information on J. Appl. Phys. A convenient method is proposed for the measurement of the characteristic free volumes, viz., the amount of excess free volume annihilation in structural relaxation V f-sr and the amount of new free volume production in glass transition V f-gt of bulk metallic glasses (BMGs) by thermal dilation (DIL) test. Through the DIL tests, the characteristic free volumes are found to be sensitive to the change of glass forming ability (GFA). The Pd 40 Cu 30 Ni 10 P 20 BMG has a quite small V f-sr . For a series of Fe-Cr-Mo-C-B-(Er) BMGs, Fe 48 Cr 15 Mo 14 C 15 B 6 Er 2 with the largest GFA is identified to have the largest V f-gt and smallest V f-sr . The correlation between V f-sr and the squares of critical diameters of these iron-based BMGs can be fitted as a negative exponential function with high accuracy.

Effect of Alloying Elements with Positive Heat of Mixing on the Free Volume and Compressive Plasticity in ZrCoCuAl Bulk Metallic Glasses

“…The C p of the as-cast BMG will then increase abruptly above T r end , which corresponds to glass transition into the supercooled liquid region. The corresponds to the temperature at the end of the structural relaxation as well as the onset of glass transition T g onset , 28) which is consistent with the results of the current study. The structural relaxation enthalpies ("H) for the as-cast BMGs are calculated by integrating the specific heat difference between the as-cast BMG and the fully crystallized alloy over the temperature range of T r onset and T r end .…”

“…Alloy ingots with nominal compositions of Zr 56 Co 28¹x Cu xAl 16 (x = 0, 3,6,12,15,21,28) were prepared from high purity elements (purity > 99.8 mass%) by arc melting the mixture of the elements in a Ti-gettered high purity argon atmosphere. Cylindrical alloy rods of 2 mm diameter were prepared from these ingots by water-cooled copper mold casting.…”

“…The reasons for selecting this alloy and the alloying element for the present study are: (1) Zr 56 Co 28 Al 16 has a large glass forming ability (GFA); 15) (2) Cu and Co have a moderate degree of positive heat of mixing of +6 kJ/mol, 16) which is a typical value of the heat of mixing between the alloying element and the constituent element of the base alloy; (3) Cu and Co have a similar atomic radius (atomic radius of Cu and Co are 0.128 and 0.125 nm respectively 17) ). With the moderate degree of positive heat of mixing between Cu and Co and the similarity in their atomic radii, it is expected that the substitution of Co with Cu can increase the amount of free volume for the Zr 56 Co 28 Al 16 BMG, without drastically reducing its glass forming ability.…”

Radiation response of amorphous metal alloys: Subcascades, thermal spikes and super-quenched zones

“…In metals, the elevated fictive temperature of SQZs is connected with a reduced density, q SQZ , i.e. increased free volume [46,54]. Thus, the density of amorphous metals is expected to decrease under irradiation.…”

Characteristic free volume change of bulk metallic glasses

“…9,11,12,[26][27][28] It is thus possible to measure the free volume change using the thermal dilatation (DIL) test, and a DIL test-based method for measuring DV f ðTÞ was recently developed. 1 The characteristic free volume change, i.e., the free volume released in structural relaxation DV f-sr , is identified quantitatively from the DV f ðTÞ curve. For a series of Fe-(Er)-Cr-Mo-C-B BMGs, DV f-sr is sensitive to and closely correlated with GFA.…”