A Computational Design Study of Self-healing Creep Resistant Steels

(1)

Delft University of Technology

Fu, Yifan; van Dijk, Niels; van der Zwaag, Sybrand Publication date

2018

Document Version Final published version

Citation (APA)

Fu, Y., van Dijk, N., & van der Zwaag, S. (2018). A Computational Design Study of Self-healing Creep Resistant Steels. Poster session presented at Dutch Materials 2018, Utrecht, Netherlands.

Important note

To cite this publication, please use the final published version (if applicable). Please check the document version above.

Copyright

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons. Takedown policy

Please contact us and provide details if you believe this document breaches copyrights. We will remove access to the work immediately and investigate your claim.

This work is downloaded from Delft University of Technology.

(2)

Yifan Fu1,2,*, Niels van Dijk2 and Sybrand van der Zwaag1,3

1 Novel Aerospace Materials group, Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands.

2 Fundamental Aspects of Materials and Energy group, Faculty of Applied Sciences, Delft University of Technology, Delft, The Netherlands. 3 School of Materials Science and Engineering, Tsinghua University, Beijing, China.

*_{E-mail: y.fu-1@tudelft.nl}

A Computational Design Study of

Self-healing Creep Resistant Steels

References

[1] S. Zhang, C. Kwakernaak, W.G. Sloof, E. Brück, S. van der Zwaag, N.H. van Dijk, Adv. Eng. Mater., 17 (2015) 598-603. [2] Q. Lu, W. Xu, S. van der Zwaag, Philos. Mag., 93 (2013) 3391-3412.

Background

Model Description

Future Work

Self-healing behaviour [1] _{Precipitation-based self-healing alloy}

Tem per atu re % Healing agent Matrix Matrix + Precipitate Super-saturation Homogenisation temperature Service temperature

Solubility of the precipitate in the matrix

Model alloys： Fe-Cu, Fe-Au, Fe-Mo, Fe-W

• Aim: a multi-elemental, self-healable, creep resistant ferrous system with adequate mechanical properties for elevated temperature use.

• Enough healing agent: volume fraction of precipitation phase > 1 %;

• Selectivity: precipitates form only on free surface

T

x T_service

Too much driving force: bulk precipitation Not enough driving force:

no precipitation

Free surface precipitation ∆𝑇𝑇

∆𝑥𝑥

Maximum selectivity at T_service

Chemical driving force ∆𝐺𝐺_𝑉𝑉 = 0

Effective driving force (∆𝐺𝐺𝑉𝑉 − ∆𝐺𝐺𝑆𝑆) = 0

∆𝐺𝐺_𝑆𝑆 = 𝜀𝜀𝑉𝑉2𝐸𝐸𝑝𝑝𝐸𝐸𝑚𝑚 3 2 1 − 2𝜈𝜈_𝑝𝑝 𝐸𝐸_𝑚𝑚 + (1 + 𝜈𝜈_𝑚𝑚)𝐸𝐸_𝑝𝑝 𝜀𝜀_𝑉𝑉′ : volume misfit E: Young’s modulus 𝜈𝜈: Poisson’s ratio p: precipitate; m: matrix 0 2 4 6 8 10 600 700 800 900 1000 1100 1200 13000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Chemical driving force = 0

W content (at.%) W content (wt.%) Tem per at ur e ( K ) VF of precipitate = 1 % Effective driving force = 0

0 1 2 3 4 5 6 7 8 300 400 500 600 700 800 900 1000 1100 12000.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

Tem per at ur e ( K ) Mo content (at. %)

Effective driving force = 0 VF of precipitate = 1 % 500 600 700 800 900 1000 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Cu content (wt.%)

Effective driving force = 0

Tem per at ur e ( K ) VF of precipitate = 1 % Cu content (at.%)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 800 850 900 950 1000 1050 1100

0.0 1.0 2.0 3.0 4.0 Tem per at ur e ( K ) Au content (at.%) Au content (wt.%)

• Cu: little shift of the solubility line due to minor volume misfit; • Au: unlimited selectivity

Alloy Candidates Go/ No Go Module Optimisation Module

Design of self-healing alloys

Design for creep resistance • High strength martensite matrix • Limited undesirable phases • Corrosion resistance • M_S > 250 oC

• Adequate molar fraction of matrix phase

• Cr content > 8 wt.% in the matrix

• Precipitation strengthening : inversely proportional to the inter-particle spacing L[2]

• L increases during the coarsening of precipitates • Aim for a small L and a low coarsening rate K.

3 3 0 3 3 0 / / r r Kt L r f r Kt f − = = = + _/ / 2 1 8 ( ) 9 / m c i i i _i _i V K x x x D RT β β α β α β γ = = −

∑

_{• Parameters can be calculated by Thermo-Calc}

• To determine the optimal composition for the first generation creep resistant steel with the self-healing capability;

• The study of the creep behaviour of the designed alloy; the research on the mechanism properties after the healing behaviour; • Model development and optimisation: the change in the driving force for precipitation during the healing process.

Damage formation

Self Healing