Test environments and mechanical properties of Zr-base bulk amorphous alloys

Abstract

The mechanical properties of two Zr-base bulk amorphous alloys (BAA), Zr-10Al-30Cu-5Ni (BAA-10) and , were studied by both tensile and compressive tests at room temperature in various test environments. The BAA ingots up to 7 mm in diameter were successfully produced by both arc melting and drop casting and induction melting and injection casting. The BAA specimens deformed mainly elastically, followed by catastrophic failure along shear bands. Examination of the fracture region revealed ductile fracture features resulting from a substantial increase in temperature, which was attributable to the conversion of the stored elastic strain energy to heat. Surprisingly, ''liquid droplets'' located at major shear-band cracks adjacent to the fracture section were observed, indicating the occurrence of local melting during fracture. The angle orientation of shear bands, shear-band cracks, and fracture surfaces relative to the stress axis is quite different for BAA specimens tested in tension and compression. This suggests that both shear stress and normal stress may play a role in developing shear bands during plastic deformation. The tensile properties of BAAs were found to be insensitive to the test environment at room temperature. However, the reaction of BAAs with distilled water and heavy water was detected by laser desorption mass spectrometry (LDMS). These results suggest that moisture-induced hydrogen embrittlement in BAAs may be masked by catastrophic fracture following shear bands.

Strain rate-dependent compressive deformation behavior of Nd-based bulk metallic glass

“…The present experimental result that the failure stress increases with increasing strain rate is in contrast to Hufnagel et al's experimental observation for a Zr-based BMG [26]. This difference demonstrates that BMGs deform by a shear banding mechanism is material-related [4]. As is illustrated in Fig.…”

“…cluster structure. Simultaneity, as demonstrated in Liu et al [4] and Hufnagel et al's discussions [26], adiabatic heating plays an important role in the deformation by a shear banding. The effect of adiabatic heating in the deformation of BMGs also makes the BMGs deform by a shear banding mechanism is material-related because materials with different chemical components have different physical properties, e.g.…”

“…Recently, due to the development of bulk metallic glasses (BMGs), intensive efforts have been focused on the preparation and mechanical deformation behaviors of BMG because of the basic science and potential engineering application of the materials [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. This class of materials exhibit many unique mechanical properties, e.g.…”

Strain distribution in Zr64.13Cu15.75Ni10.12Al10 bulk metallic glass investigated by in situ tensile tests under synchrotron radiation

“…[3][4][5][6][7][8][9][10][11][12] At temperatures below or around the glass transition and rather high strain rates metallic glasses deform by the formation of localized shear bands, [3][4][5]8 whereas homogeneous flow of the supercooled liquid is observed at elevated temperatures and/or low strain rates. 13,14 For the former case, it was previously considered that the compressive fracture usually proceeds along a shear plane inclined by 45°to the loading axis, 15 i.e., the maximum shear stress plane. However, several recent systematic investigations on glasses in different alloy systems indicate that the shear fracture always deviates from the maximum shear stress plane either under compression or under tension.…”

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

“…1 Such a catastrophic fracture extremely limits the application of metallic glasses as structural materials, and is attributed by many researchers to the lack of work hardening in metallic glasses under plastic deformation. 2,3 However, microstructure examinations have revealed the existence of crystalline phases in the shear bands, [4][5][6][7] indicating that the fracture progress is accompanied by a partial crystallization, and the effect of crystallization on the fracture cannot be excluded. In order to understand how metallic glasses change their mechanical properties when they are subjected to severe plastic deformation and do not crystallize, further investigation is needed.…”