Structural Relaxation and Crystallization of a Zr<SUB>44</SUB>Ti<SUB>11</SUB>Cu<SUB>9.8</SUB>Ni<SUB>10.2</SUB>Be<SUB>25</SUB> Bulk Metallic Glass

Abstract

The influence of annealing on the structural changes and the room temperature mechanical properties of a Zr 44 Ti 11 Cu 9:8 Ni 10:2 Be 25 bulk metallic glass has been investigated. The structural evolution upon relaxation or crystallization after annealing at a temperature within the supercooled liquid region was studied by thermal analysis, x-ray diffraction, transmission electron microscopy, extended x-ray absorption fine structure and dilatometer measurements. The effects of structural relaxation and nanocrystallization on the mechanical properties were also examined by hardness and compression tests using specimens annealed for various times. The apparent disappearance of plastic strain was found to be due to embrittlement induced by considerable crystallization of the amorphous phase.

Structural and mechanical properties of Ni60Nb40 amorphous alloy particle reinforced Al-based composites produced by microwave-assisted rapid sintering

“…However, it should be noted that structural relaxation is strongly time-dependent and usually occurs in bulk of the sample causing large dilatation in amorphous alloys/BMG (∼3%, Fig. 4 [16,21]). In the present work, there is no holding time involved during sintering.…”

“…This implies a decrease in the distance between nearest-neighbor atoms. Such a decrease in the atomic distance in the amorphous phase can lead to structural dilatation and eventually to nanocrystallization (usually observed in amorphous alloys [16][17][18][19][20][21]). In Fig.…”

“…A comparison between the dilatation values of the current composites with those of various amorphous alloys/BMGs (from literature [16][17][18][19][20][21]) has been made. Usually, in amorphous alloys/ BMG, structural dilatation is known to occur: (i) due to external solute atom addition (such as hydrogen) [17,18], (ii) during deformation at high temperatures (stress-induced; controlled by strain rate) [19,20], and (iii) by structural relaxation [16,21] during annealing (causes annihilation of free volume present in amorphous structure and is time-dependent). To understand the dilatation observed in the developed composites, factors (ii) and (iii) are applicable and are discussed below.…”

On the structural relaxation of bulk metallic glass under warm deformation

“…The hardness of BMGs is reported to continuously increase upon structural relaxation, possibly because the excess free volume in the glass is annealed out, which is known to enhance the atomic bonding strength after annealing [19,20]. Furthermore, it is well known that structural relaxation-induced embrittlement has a detrimental effect on plastic deformation.…”

Crystallization and thermal fatigue of ZrTiCuNiBe bulk amorphous alloys heated by laser pulses

“…Studies of the thermal stability of amorphous alloys are of great importance. Although many research studies explore structures and properties of amorphous alloys during annealing [4][5][6], few studies are reported regarding the influence of circle heating on the stability of bulk amorphous alloys. This paper uses laser pulses as a heat source to investigate crystallization and thermal fatigue properties of the typical Zr 41 Ti 14 Cu1 2.5 Ni 10 -Be 22.5 bulk amorphous alloy.…”