Results of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr-Ti-Cu-Ni-Be alloy system. The calorimetric data for five alloys, prepared along the tie line between phase separating and nonphase separating compositions, show that the transition from phase separating to nonphase separating behavior is smooth. The bulk glasses near the center of the tie line exhibit large supercooled liquid regions: ⌬TϷ135 K, the largest known for a bulk metallic glass. © 1999 American Institute of Physics. ͓S0003-6951͑99͒01734-9͔There are a number of multicomponent bulk metallic glass ͑BMG͒ forming alloy systems, e.g., La-Ni-Al, 1 Zr-Al-Cu-Ni, 2 Zr-Ti-Cu-Ni-Be, 3 and Zr-Ti-Cu-Ni. 4 The Be-containing bulk glass Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 ͑Vit 1͒ exhibits an exceptional glass forming ability ͑GFA͒ and thermal stability with respect to crystallization. The liquidstate viscosity of the Be-BMG alloys is Ϸ two orders of magnitude higher than in pure metals or alloys, typically (Be-BMG)Ϸ5 poise. 5 The high melt viscosities of the Be-BMG compositions yield very sluggish crystallization kinetics in the supercooled liquid region ͑SLR͒. The crystallization behavior of Vit 1 has been determined by electrostatic levitation ͑ESL͒ and calorimetric methods. 6,7 These results, when combined with the results of small angle neutron scattering ͑SANS͒ measurements conducted by Schneider, Johnson, and Thiyagarajan show that primary crystallization is preceded by phase separation in the SLR. 8 This phase separation process shows many of the features of a spinodal decomposition, with a spinodal temperature of Ϸ 671 K. The decomposition process is followed by the nucleation of fcc nanocrystals on a length scale correlated with the spinodal wavelength, s Ϸ14 nm. The bulk glass Zr 46.75 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 ͑Vit 4͒ also exhibits an excellent GFA. This alloy exhibits little phase separation prior to crystallization. To elucidate this behavior, results of thermophysical property measurements are presented for compositions along the tie line between the compositions of Vit 1 and Vit 4, the phase separating and nonphase separating alloys, respectively. The thermophysical property data show that through controlled changes in alloy composition the GFA may be altered drastically. The experimental data are related to the known features of the Vit 1 time-temperaturetransformation ͑TTT͒ diagram determined from the ESL measurements.The details of the methods used to prepare the master alloys are described elsewhere. 9 The tie-line alloy compositions were prepared in the form of thin strips, 1ϫ5ϫ Ϸ25 mm ͑thickness by width by length͒, by injection casting into a Cu metal mold. The specimen compositions prepared along the tie line from Vit 1 to Vit 4, labeled Vit 1, 1͑a͒, 1͑b͒, 1͑c͒, and 4, respectively, are presented in Table I. The nominal compositions are used in this letter. The strategy employed in this alloy series involves incrementally changin...

No abstract