Room-temperature creep resistance of Co-based metallic glasses

Abstract

The room-temperature creep resistance of the Co 56 Ta 9 B 35 metallic glass was determined by a nanoindentation technique. Results showed that the creep curves were described by a generalized Kelvin model. The low creep strain-rate sensitivity parameter and creep rate derived from the displacement-holding time curves demonstrated the high creep resistance of the Co 56 Ta 9 B 35 metallic glass. The deformation mechanism causing the nanoindentation creep was discussed based on the "shear transformation zone" concept, which gave an explanation for the creep behavior in metallic glasses. A number of Co-based multicomponent metallic glass (MG) systems have been reported, including Co-Fe-(Ta,Mo)-(B,Si) [1-4], (Co-Fe)-(Nb,Zr)-(B,Si) [5-9], (Co,Fe,Ni)-(Zr,Hf,Nb,Ta,Mo,W)-B [10] and Co-Fe-B-Si [11]. The family of Co-based MGs has been widely studied in recent decades. A wide range of material properties have been investigated, including glassforming ability [7-9], thermal stability, strength [1][2][3]8] and magnetic properties [2,7,[9][10][11]. For instance, the Co 43 Fe 20 Ta 5.5 B 31.5 MG has been reported to be the strongest MG [2] with promising magnetic applications [1,2,4,[12][13][14]. The tensile strengths of Co-Si-B and Co-Ta-Si-B alloys have been reported to range from 3580 to 4000 MPa, respectively. When Fe is removed from the Co-Fe-Ta-B ribbon and wire MGs [12], the fracture strength of Co-based MGs can even increase to above 6000 MPa.Co 65 À x Ta x B 35 (at.%, x = 5-11) [12,15] systems have rapidly become of broad interest, having set the record for the highest strength among the known bulk glassy alloys, with an elastic modulus and hardness of 280 and 17.8 GPa, respectively. Our recent research [15,16] on the compressibility of CoTaB MGs under high pressure by using synchrotron radiation X-ray diffraction (XRD) confirmed that the charge density and bonding character demonstrate that the covalent character of Co-B and B-B bonds is the reason for the high elastic modulus and hardness in CoTaB MGs [15].Very recently, a plasticity ternary Co 61 Nb 8 B 31 bulk MG was fabricated with a plasticity of 5% and a yield strength of 5200 MPa [17]. However, the room-temperature creep-resistance behavior of Co-based MGs has not been reported. The plastic deformation of MGs and the related mechanism are considered to be among the most important aspects of their engineering application. Thus, studying the creep-resistance behavior of materials can enable the selection of appropriate materials in different environments. Given the size limitation of MGs, many of their mechanical properties cannot be studied by traditional methods. A new nanoindentation technique has recently paved a new path for research on the plastic deformation of glassy alloys [18]. Therefore, in this work, we use Co 56 Ta 9 B 35 as a model MG to study the creep-resistance behavior at room temperature using the nanoindentation technique.The amorphous ribbon was prepared by the meltspinning technique in an argon atmosphere. The glassy structure of the alloys ...

A first approach on the assessment of the creep behavior of MoTaNbVxTi high entropy alloys by indentation testing

“…Additionally, as Li et al [4] and Yu et al [13] proposed, the indentation creep obeys an empirical power law of the form:…”

Indentation of glasses

“…While atomistic simulations have suggested that such loads can produce irreversible changes in the glass structure [216], creep-like behavior at RT was experimentally observed through uniaxial elastostatic compression tests in mm-sized MG samples [217,218]. Hence, time-dependent plastic deformation, or creep, at RT in a wide variety of MGs has been investigated using nanoindentation [219][220][221][222][223][224][225][226][227]. Results show that creep occurs at RT irrespective of whether T g is low or high, and the measured response is sensitive to both intrinsic material features such as the chemical composition [228] and the nature of initial structural defects [223,225], as well as external testing conditions such as the [223,226] and imposed strain [224,227]).…”

Tensile Creep Characterization and Prediction of Zr-Based Metallic Glass at High Temperatures

“…Creep behavior is a critical issue of practical engineering significance for the applications of BMGs. Recently, the creep behaviors of BMGs have been reported using compression tests and nanoindentation technology [6][7][8][9][10][11][12][13][14][15]. Huang et al studied the room temperature creep behaviors of a Fe 41 Co 7 Cr 15 Mo 14 C 15 B 6 Y 2 BMG using the nanoindentation technique and found that the creep exponent varied with the peak load or loading rate, which has been interpreted based on the shear transformation zone theory [6].…”

“…Huang et al studied the room temperature creep behaviors of a Fe 41 Co 7 Cr 15 Mo 14 C 15 B 6 Y 2 BMG using the nanoindentation technique and found that the creep exponent varied with the peak load or loading rate, which has been interpreted based on the shear transformation zone theory [6]. Yu et al suggested that the nanoindentation creep behaviors of Co 56 Ta 9 B 35 metallic glass could be described by a Kelvin model [7]. However, it should be noted that the nanoindentation creep is sensitive to the ambient environment, and the different holding times used in creep tests in previous literature have caused paradoxical results.…”