Crystallization of Cu₆₀Ti₂₀Zr₂₀ metallic glass with and without pressure

Abstract

Structural stability of a Cu 60 Ti 20 Zr 20 metallic glass under pressure up to 4.5 GPa was investigated by x-ray diffraction. The sample exhibited a supercooled liquid region of 33 K and a ratio of the glass-transition temperature to the liquidus temperature of 0.63. The glass crystallized in two-step transformation processes in the pressure range of 0-4.5 GPa; the first was a primary reaction to form a Cu 51 Zr 14 -type structure crystalline phase with a spacing group P6/m (175) and lattice parameters a ‫ס‬ 11.235 Å and c ‫ס‬ 8.271 Å, and then the residual amorphous phase crystallized into a MgZn 2 -type structure crystalline phase with a spacing group P6 3 /mmc (194) and lattice parameters a ‫ס‬ 5.105 Å and c ‫ס‬ 8.231 Å. Both crystallization temperatures increased with pressure having a slope of 19 K/GPa. The increase of the first crystallization temperature with increasing pressure in the glass can be explained by the suppression of atomic mobility. No significant structural change was detected in the Cu 60 Ti 20 Zr 20 glass annealed in vacuum at 697 K for 1 h as compared to the as-prepared sample from x-ray diffraction measurements.

Origin of nondetectable x-ray diffraction peaks in nanocomposite CuTiZr alloys

“…The DSC curve for the as-cast rod is in good agreement with data reported in the literature. [5][6][7][8][9][10][11][12] With increasing annealing time, the enthalpy of the first exothermic peak monotonically decreases from 25 J/g for the as-cast rod to about 5 J/g for the sample annealed for 7.8 ks, while the second exothermic peak remains almost unchanged within experimental uncertainty. With further increasing annealing time, the second exothermic peak starts to decrease and its position shifts to low temperatures.…”

“…[2][3][4] Very recently, the report of ternary Cu 60 Ti 10 Zr 30 and Cu 60 Ti 15 Hf 25 systems, 5,6 exhibiting excellent mechanical properties, has triggered considerable research activity in this area, especially in the microstructure of the ternary systems. [5][6][7][8][9][10][11][12] Inoue et al, 5,6 reported that bulk glassy alloys with a rod diameter of 4 mm can be formed in the ternary Cu 60 Ti 10 Zr 30 and Cu 60 Ti 15 Hf 25 systems. However, only the x-ray diffraction ͑XRD͒ technique was applied to characterize the samples.…”

“…It is concluded that the as-prepared ternary samples are classified as a nanocomposite: nanocrystals embedded in an amorphous matrix. However, one experimental fact reported in the literature [5][6][7][8][9][10][11][12] still remains a puzzle for the community, i.e., no diffraction peaks from the nanocrystalline component were detected in the XRD patterns recorded for the as-cast or as-spun Cu 60 Ti 10 Zr 30 samples. In this letter, we uncover the origin of the puzzle by performing TEM, XRD and differential scanning calorimeter ͑DSC͒ measurements of asprepared and annealed Cu 60 Ti 10 20 Zr 20 samples were prepared by the meltspinning method.…”

Extensions and some recent applications of the Landau theory of phase transitions

“…Recrystallization of amorphous phases under pressure has been observed in amorphous − quartz [62], which transforms into stishovite at about 60 GPa, and for the high-density amorphous phase of ice [63], which recovers the ice VII or ice VIII structure at high pressure. Recrystallization under pressure or stress is also observed in a number of glasses [64]. On the other hand, superhard properties, i.e.…”

Mechanically driven phase separation and corresponding microhardness change in Cu60Zr20Ti20 bulk metallic glass

“…12,13 DSC measurements of the as-rolled specimens with different indicate that the areas of the both exothermic peaks are almost unchanged compared to the as-cast specimen ͑not shown here͒. So, the possibility of crystallization in the asrolled specimens can be excluded.…”