Correlations between elastic moduli and properties in bulk metallic glasses
Wei Hua Wanga_
Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
_Received 18 October 2005; accepted 21 January 2006; published online 12 May 2006_
A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses
_BMGs_ and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have
correlations with the glass transition temperature, melting temperature, mechanical properties, and
even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough
correlation with a weighted average of the elastic constants for the constituent elements. Although
the theoretical and physical reasons for the correlations are to be clarified, these correlations could
assist in understanding the long-standing issues of glass formation and the nature of glass and
simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist
in selecting alloying components for controlling the elastic properties and glass-forming ability of
the BMGs and thus can guide BMG design. As case study, we report the formation of the families
of rare-earth-based BMGs with controllable properties. © 2006 American Institute of Physics.
_DOI: 10.1063/1.2193060_
I. INTRODUCTION
The mechanism of glass formation, the nature of glass,
and the design of metallic glassy composition with excellent
glass-forming ability _GFA_ and controllable properties are
one of the central issues in condensed matter physics and
material science. Substantial progress has been made in understanding
these issues over the past decades, yet many key
questions remain.1–3 Although some rather general empirical
rules, based on the thermodynamic, kinetic, and microstructural
features, give useful directions in general,1,3–5 the development
of bulk metallic glass _BMG_, in practical, has
always been “hit or miss” whether the resulting glass has
excellent GFA or would turn out to be excellent in some
properties.5 Therefore, finding a more specific criterion for
BMG formation, based on the insightful understanding of the
nature of the glass, is of high significance.
Metallic glassy alloys are normally regarded as elastically
isotropic, and they behave as an elastic continuum at
low temperatures, with a well-defined dispersion relation so
that ultrasonic waves propagated through it.3–7 With the recent
development of metallic glasses which readily form
bulk glass, studies of the elastic properties using ultrasonic
method have yielded a wealth of experimental elastic data
previously inaccessible in metallic glasses owing to the small
size. On the other hand, significant amounts of data have
been collected on mechanical properties _e.g., fracture
strength _, fracture toughness KC, Vicker’s hardness Hv_.3–7
For example, the Ce-based BMGs with the lowest elastic
moduli values _e.g., Young’s modulus E _30 GPa_ are comparable
to those of oxide fused quartz and close to those of
Wei Hua Wanga_
Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
_Received 18 October 2005; accepted 21 January 2006; published online 12 May 2006_
A survey of the elastic, mechanical, fragility, and thermodynamic properties of bulk metallic glasses
_BMGs_ and glass-forming liquids is presented. It is found that the elastic moduli of BMGs have
correlations with the glass transition temperature, melting temperature, mechanical properties, and
even liquid fragility. On the other hand, the elastic constants of available BMGs show a rough
correlation with a weighted average of the elastic constants for the constituent elements. Although
the theoretical and physical reasons for the correlations are to be clarified, these correlations could
assist in understanding the long-standing issues of glass formation and the nature of glass and
simulate the work of theorists. Based on the correlation, we show that the elastic moduli can assist
in selecting alloying components for controlling the elastic properties and glass-forming ability of
the BMGs and thus can guide BMG design. As case study, we report the formation of the families
of rare-earth-based BMGs with controllable properties. © 2006 American Institute of Physics.
_DOI: 10.1063/1.2193060_
I. INTRODUCTION
The mechanism of glass formation, the nature of glass,
and the design of metallic glassy composition with excellent
glass-forming ability _GFA_ and controllable properties are
one of the central issues in condensed matter physics and
material science. Substantial progress has been made in understanding
these issues over the past decades, yet many key
questions remain.1–3 Although some rather general empirical
rules, based on the thermodynamic, kinetic, and microstructural
features, give useful directions in general,1,3–5 the development
of bulk metallic glass _BMG_, in practical, has
always been “hit or miss” whether the resulting glass has
excellent GFA or would turn out to be excellent in some
properties.5 Therefore, finding a more specific criterion for
BMG formation, based on the insightful understanding of the
nature of the glass, is of high significance.
Metallic glassy alloys are normally regarded as elastically
isotropic, and they behave as an elastic continuum at
low temperatures, with a well-defined dispersion relation so
that ultrasonic waves propagated through it.3–7 With the recent
development of metallic glasses which readily form
bulk glass, studies of the elastic properties using ultrasonic
method have yielded a wealth of experimental elastic data
previously inaccessible in metallic glasses owing to the small
size. On the other hand, significant amounts of data have
been collected on mechanical properties _e.g., fracture
strength _, fracture toughness KC, Vicker’s hardness Hv_.3–7
For example, the Ce-based BMGs with the lowest elastic
moduli values _e.g., Young’s modulus E _30 GPa_ are comparable
to those of oxide fused quartz and close to those of
