Inverse ductile–brittle transition in metallic glasses?

Abstract

There is evidence that metallic glasses can show increased plasticity as the temperature is lowered. This behaviour is the opposite to what would be expected from phenomena such as the ductile-brittle transition in conventional alloys. Data collected for the plasticity of different metallic-glass compositions tested at room temperature and below, and at strain rates from rate 10 25 to 10 3 s 21 , are reviewed. The analogous effects of low temperature and high strain rate, as observed in conventional alloys, are examined for metallic glasses. The relevant plastic flow in metallic glasses is inhomogeneous, sharply localised in thin shear bands. The enhanced plasticity at lower temperature is attributed principally to a transition from shear on a single dominant band to shear on multiple bands. The origins of this transition and its links to shear bands operating 'hot' or 'cold' are explored. The stress drop on a shear band after initial yielding is found to be a useful parameter for analysing mechanical behaviour. Schematic failure mode maps are proposed for metallic glasses under compression and tension. Outstanding issues are identified, and design rules are considered for metallic glasses of improved plasticity.

Properties of selected structural and flat flexible cabling materials for low temperature applications

“…The high elastic limit is concomitant with a high elastic storage capability, with minimal loss. Bulk metallic glasses exhibit an increase in plasticity (ductility or fracture toughness) as their temperature is lowered [29], a potentially useful characteristic for cryogenic structural support applications. Though the amorphous phase is not thermodynamically stable, they exhibit metastability at and below room temperature for sufficiently long times to allow their use in structural applications.…”

Compressive plasticity of a La-based glass-crystal composite at cryogenic temperatures

“…Figure 1b shows a magnified view of the plastic part of the stress-strain curve for samples tested at 77 Kno serrations can be seen and neither are multiple shear bands visible on the sides of the compression specimens (not shown here). This suggests that the small plastic strain is a result of retarded sliding on a single shear band [26,27], in contrast to multiple shear banding seen in other BMGs, e.g.…”

Effects of heat treatment on HVOF-sprayed Fe-based amorphous coatings

“…Fe-based bulk metallic glass (BMG) exhibits excellent mechanical, physical and chemical properties, such as high strength, soft magnetic, excellent corrosion resistance, making BMG have broad application prospect [1][2][3]. However, most BMG cannot be used as structural material, because its plasticity at room temperature is poor and exhibiting brittle fracture.…”