Elevated Temperature Deformation Behavior of Zr‐Based Bulk Metallic Glasses

Abstract

Within the last decade, metallic glassy alloys in bulk form produced by slow cooling from the melt [1±4] have attracted widespread interest ranging from scientific curiosity about the structure and the resulting properties to technological aspects of preparation and potential applications. In contrast to binary and ternary amorphous metallic systems produced in form of thin ribbons, these multi-component alloys are characterized by a strong glass-forming ability (GFA) together with a wide supercooled liquid region, thus giving rise to a high thermal stability against crystallization. This enables the production of bulk glassy samples with a thickness of up to 75 mm by conventional casting techniques. [13] Besides their thermodynamic properties Zr-based bulk metallic glasses (BMGs) in particular reveal outstanding mechanical properties at room temperature, [5±8] namely a beneficial combination of yield strength values as high as those known for high-strength structural steels, microplasticity of up to 1 %, low Young's moduli and high fracture toughness values comparable to those of aluminum alloys. The desirable properties of the amorphous phase together with the reported easy forming and shaping ability in the viscous state at elevated temperatures above the glass transition [11] promise applications in the field of near-net shape fabrication of structural components. [12,13] In the present work, we will review the deformation mechanism in the supercooled liquid state, since it is of paramount importance to identify and assess the temperature COMMUNICATIONS ADVANCED ENGINEERING MATERIALS 2005, 7, No. 9

Homogeneous flow of bulk metallic glass composites with a high volume fraction of reinforcement

“…This volume is around the normal size expected for shear transformation zones, 52,53 and in fact it compares quite reasonably with other measurements in the literature. Table II compiles values of V from various studies on a number of glasses 23,29,33,35,37,39,[41][42][43]47,52,[54][55][56][57][58][59][60] ; the original data from these papers were either directly re-fitted with Eq. (1), or reported fitting parameters were translated to the form of Eq.…”

The Effect of Forming Speed on the Formability of a Zr-Based Bulk Metallic Glass

“…At the stage of Newtonian flow (at low strain rate), the flow stress rises linearly with the increase in strain rate. While at the stage of non-Newtonian flow, the flow stress maintain nearly constant independent of strain rate [8] . Since under the non-Newtonian rheology, the deformation behavior of metallic glasses is close to that of plastic material than that of viscous material, it desirable to deform the metallic glasses at high strain rate.…”

“…In recent years, there are many reports on the study of flow deformation and forming-ability of metallic glasses [8][9][10][11] , and on the study of the formation of micro-parts [12][13][14][15] . Saotome et al studied the extrusion forming of the micro parts of metallic glasses [6; 16-18] .…”

Viscosity-related properties of Mg65Cu25Y10 bulk metallic glass determined by uniaxial tension in the supercooled liquid region

“…On the other hand, with the advance of time, the supercooled liquid moves away from a highly non-equilibrium state towards a lower energy state. This phenomenon, which is an internal atomic rearrangement without significant long-range atomic migration, is called relaxation [3], whereby the structural relaxation time increases with decreasing temperature. Numerous models have been proposed to account for the temperature dependence of viscosity or relaxation time.…”