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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

Comparison of predicted results and experimental data (a) 694 K, 0.01 s−1, and (b) 704 K, 0.005 s−1 with different sample sizes, (c) 1 mm, 0.01 s−1 at different temperatures (d) 1 mm, 694 K with different strain rates.
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f5: Comparison of predicted results and experimental data (a) 694 K, 0.01 s−1, and (b) 704 K, 0.005 s−1 with different sample sizes, (c) 1 mm, 0.01 s−1 at different temperatures (d) 1 mm, 694 K with different strain rates.

Mentions: Based on the size-dependent Maxwell-pulse type constitutive model, the true stress–strain curves of different sized BMG samples are fitted, as shown in Figure 5. The dashed lines represent the true stress–strain curves obtained from micro cylinder compression experiments while solid lines stand for the results predicted by the proposed constitutive model. It can be seen that the curves of the proposed constitutive model agree with those of experiment of BMGs in the SCLR. It also reproduces the size-dependent transition from non-Newtonian to Newtonian flow, which plays a key role in the application of BMGs in micro thermoplastic forming.


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)

Comparison of predicted results and experimental data (a) 694 K, 0.01 s−1, and (b) 704 K, 0.005 s−1 with different sample sizes, (c) 1 mm, 0.01 s−1 at different temperatures (d) 1 mm, 694 K with different strain rates.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Comparison of predicted results and experimental data (a) 694 K, 0.01 s−1, and (b) 704 K, 0.005 s−1 with different sample sizes, (c) 1 mm, 0.01 s−1 at different temperatures (d) 1 mm, 694 K with different strain rates.
Mentions: Based on the size-dependent Maxwell-pulse type constitutive model, the true stress–strain curves of different sized BMG samples are fitted, as shown in Figure 5. The dashed lines represent the true stress–strain curves obtained from micro cylinder compression experiments while solid lines stand for the results predicted by the proposed constitutive model. It can be seen that the curves of the proposed constitutive model agree with those of experiment of BMGs in the SCLR. It also reproduces the size-dependent transition from non-Newtonian to Newtonian flow, which plays a key role in the application of BMGs in micro thermoplastic forming.

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