Ductile Bulk Metallic Glass

Abstract

We report on experimental evidence of pronounced global plasticity measured in monolithic Pt 57:5 Cu 14:7 Ni 5:3 P 22:5 bulk metallic glass under both bending and unconfined compression loading conditions. A plastic strain of 20% is measured, never before seen in metallic glasses. Also, permanent deformation and a strain exceeding 3% before failure is observed during bending of 4 mm thick samples. To date, no monolithic metallic material has exhibited such a combination of high strength, extensive ductility, and high elastic limit. The large plasticity is reflected in a high Poisson ratio of 0.42, which causes the tip of a shear band to extend rather than initiate a crack. This results in the formation of multiple shear bands and is the origin of the observed large global ductility and very high fracture toughness, approximately 80 MPa m ÿ1=2 .

Towards more uniform deformation in metallic glasses: The role of Poisson's ratio

“…(14) and (15) show that, other factors being constant, both l and Du are proportional to ð1À2nÞ=ð1ÀnÞ. Conner et al [5] obtained this result but did not explore it, as their work preceded the current intense interest in how the plasticity of MGs is correlated with their elastic properties (particularly n) [14][15][16][24][25][26]. We now calculate the dependence of l (Fig.…”

“…The link between n and plasticity was noted for metallic glasses by Chen et al [13], and was explored quantitatively by Lewandowski et al [14], who found a sharp transition: Metallic glasses show significant toughness only when n exceeds a critical value of 0.31-0.32. This has excited interest in tuning compositions to increase n, and in this way many tough bulk MGs have been realized [15][16][17].…”

Development and Characterization of Low-Density Ca-Based Bulk Metallic Glasses: An Overview

“…Indeed, it has long been known for crystalline metals, [49] and has recently been shown for metallic glasses, [50] that the brittleness correlates with the PoissonÕs ratio m, so that when m decreases below a critical value, the metal becomes brittle. For many metallic glasses, this critical value is m cr % 0.32, [50][51][52] while the PoissonÕs ratios of Ca-based glasses at room temperature are much below 0.32 (Table V). The covalent bonding and strong liquid behavior are known to suppress atom mobility, also leading to brittleness.…”

One-dimensional solidification of supercooled melts

“…This expression for φ provides one interpretation of the usual kinetic undercooling coefficient described, for example, in [6,7,9]. The solid lines in Figure 1 were obtained by plotting equation (1) using the parameter values of Table 1, the broken lines come from equation (2).…”

“…A material formed from a supercooled liquid, usually called a glassy or amorphous solid, can present greater corrosion resistance, toughness, strength, hardness and elasticity than common materials: amorphous metal alloys can be twice as strong and three times more elastic than steel. Such materials are currently used in medicine, defence and aerospace equipment, electronics and sports [1,2,3]. Recent advances in the production and use of amorphous solids provides the motivation for this theoretical study on the solidification of a supercooled liquid.…”