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A size-dependent constitutive model of bulk metallic glasses in the supercooled liquid region.

Yao D, Deng L, Zhang M, Wang X, Tang N, Li J - Sci Rep (2015)

Bottom Line: It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size.The free volume and defect concentration were introduced to explain the size effect.Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Materials Processing and Die &Mould Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, 430074 Wuhan, Hubei, China.

ABSTRACT
Size effect is of great importance in micro forming processes. In this paper, micro cylinder compression was conducted to investigate the deformation behavior of bulk metallic glasses (BMGs) in supercooled liquid region with different deformation variables including sample size, temperature and strain rate. It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size. The free volume and defect concentration were introduced to explain the size effect. In order to demonstrate the influence of deformation variables on steady stress, elastic modulus and overshoot phenomenon, four size-dependent factors were proposed to construct a size-dependent constitutive model based on the Maxwell-pulse type model previously presented by the authors according to viscosity theory and free volume model. The proposed constitutive model was then adopted in finite element method simulations, and validated by comparing the micro cylinder compression and micro double cup extrusion experimental data with the numerical results. Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs.

No MeSH data available.


Related in: MedlinePlus

(a) The activation volume Vact(Å3) and (b) the exponential factor  of different sizes at four deformation temperatures.
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f3: (a) The activation volume Vact(Å3) and (b) the exponential factor of different sizes at four deformation temperatures.

Mentions: Figure 3 shows the activation volume and exponential factors of different sizes at four deformation temperatures. With size increasing, the activation volume of Zr55Cu30Al10Ni5 BMGs increases. Therefore, it could provide more free volume in order to satisfy the need of deformation. As is well known, the free volume is regarded as the elementary unit of plastic flow. The more activation volume, the plastic flow occurs more easily. On the other hand, the exponential factor increases with the size increasing, namely the defect concentration increases. More defect concentration provides more low strength regions, which is also beneficial for plastic deformation32.


A size-dependent constitutive model of bulk metallic glasses in the supercooled liquid region.

Yao D, Deng L, Zhang M, Wang X, Tang N, Li J - Sci Rep (2015)

(a) The activation volume Vact(Å3) and (b) the exponential factor  of different sizes at four deformation temperatures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4308703&req=5

f3: (a) The activation volume Vact(Å3) and (b) the exponential factor of different sizes at four deformation temperatures.
Mentions: Figure 3 shows the activation volume and exponential factors of different sizes at four deformation temperatures. With size increasing, the activation volume of Zr55Cu30Al10Ni5 BMGs increases. Therefore, it could provide more free volume in order to satisfy the need of deformation. As is well known, the free volume is regarded as the elementary unit of plastic flow. The more activation volume, the plastic flow occurs more easily. On the other hand, the exponential factor increases with the size increasing, namely the defect concentration increases. More defect concentration provides more low strength regions, which is also beneficial for plastic deformation32.

Bottom Line: It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size.The free volume and defect concentration were introduced to explain the size effect.Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Materials Processing and Die &Mould Technology, Huazhong University of Science and Technology, 1037 Luoyu Road, 430074 Wuhan, Hubei, China.

ABSTRACT
Size effect is of great importance in micro forming processes. In this paper, micro cylinder compression was conducted to investigate the deformation behavior of bulk metallic glasses (BMGs) in supercooled liquid region with different deformation variables including sample size, temperature and strain rate. It was found that the elastic and plastic behaviors of BMGs have a strong dependence on the sample size. The free volume and defect concentration were introduced to explain the size effect. In order to demonstrate the influence of deformation variables on steady stress, elastic modulus and overshoot phenomenon, four size-dependent factors were proposed to construct a size-dependent constitutive model based on the Maxwell-pulse type model previously presented by the authors according to viscosity theory and free volume model. The proposed constitutive model was then adopted in finite element method simulations, and validated by comparing the micro cylinder compression and micro double cup extrusion experimental data with the numerical results. Furthermore, the model provides a new approach to understanding the size-dependent plastic deformation behavior of BMGs.

No MeSH data available.


Related in: MedlinePlus