Designing and understanding novel highentropy alloys towards superior properties

Transcription

1 Designing and understanding novel highentropy alloys towards superior properties Zhiming Li

2 Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf Aalto MPIE 2

3 Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf 3

4 Outline 1. Background of high-entropy alloys (HEAs) 2. TRIP-assisted dual-phase HEAs 3. Interstitially alloyed TWIP-TRIP-HEAs 4. Summary and outlook 4

5 Outline 1. Background of high-entropy alloys (HEAs) 2. TRIP-assisted dual-phase HEAs 3. Interstitially alloyed TWIP-TRIP-HEAs 4. Summary and outlook 5

6 HEAs-Metallurgical Design Single-phase solid solution High-entropy alloy (HEA) Fe 20 Mn 20 Ni 20 Co 20 Cr 20 FCC 6

7 HEAs-Background High entropy alloys (HEAs) Definition: multi-component alloy systems; high configurational entropy S c (>R). Alloy design criteria: solid solution formation primary components 5; equiatomic or near equiatomic (5-35 at.%); G mix = H mix T S mix some proposed rules: δ, H mix, S mix, χ, VEC Candidates for many applications high compressive strength; excellent wear and oxidation resistance; thermal resistance to softening up to 7

8 HEAs-Background Single-phase FCC Fe 20 Mn 20 Ni 20 Co 20 Cr 20 Unchanged toughness From: B. Gludovatz, et al., Science, 2014, 345,

9 HEAs-Metallurgical Design Single-phase solid solution High-entropy alloy (HEA) Fe 20 Mn 20 Ni 20 Co 20 Cr 20 FCC BCC HCP 9

10 Outline 1. Background of high-entropy alloys (HEAs) 2. TRIP-assisted dual-phase HEAs 3. Interstitially alloyed TWIP-TRIP-HEAs 4. Summary and outlook 10

11 Motivations Single-phase HEA Multi-phase HEA Solid solution strengthening + Phase-interface strengthening Dislocation + Twinning + Displacive transformation Multi-phase Stress Single-phase Strain 11

12 Motivations Phase formation in HEAs Single phase solid solution Ni Cu Cr Mo Configurational entropy Solid solution Otto, F., et al., Acta Materialia, (7):

13 Motivations Fe 20 Mn 20 Ni 20 Co 20 Cr 20 Fe 80-x Mn x Co 10 Cr 10 Non-equiatomic HEAs 13

14 DP-HEAs design Fe 20 Mn 20 Ni 20 Co 20 Cr 20 Fe 80-x Mn x Co 10 Cr 10 =1928 J/mol for single phase Fe 20 Mn 20 Ni 20 Co 20 Cr Phase stability G hcp-fcc, J/mol Thermo-calc x value (Mn content) SFE: Γ 2 2 / 2 14

15 DP-HEAs design Fe 20 Mn 20 Ni 20 Co 20 Cr 20 Fe 80-x Mn x Co 10 Cr 10 Z. Li, et al., Nature 534, 227 (2016). 15

16 Elemental distribution Fe 50 Mn 30 Co 10 Cr 10 (TRIP-DP-HEA) Compositionally-equivalent high-entropy phases Z. Li, et al., Nature 534, 227 (2016). 16

17 Mechanical behavior Z. Li, et al., Nature 534, 227 (2016). Z. Li, et al., Acta Materialia 131, 323 (2017). Ref. i: Wu, X. et al., PNAS, 112, 14501(2015). Ref. ii: Kim, S.-H. et al., Nature 518, 77 (2015). 17

18 Deformation mechanisms Z. Li, et al., Nature 534, 227 (2016). 18

19 Deformation mechanisms Z. Li, et al., Acta Materialia 131, 323 (2017). Z. Li, et al., Nature 534, 227 (2016). 19

20 Quinary TRIP-HEAs Fe 40-x Mn 20 Ni x Co 20 Cr 20 (X=6 at%) ε loc =0 ε loc =20 % ε loc =40 % ε loc =60 % ε loc =100 % Z. Li, et al., Acta Materialia 136, 262 (2017). 20

21 TRIP-assisted dual-phase HEAs Rather than focusing on phase stabilization and single-phase formation, HEA design could have rewarding guidelines from phase metastability and ductile multi-phase configurations. 21

22 Outline 1. Background of high-entropy alloys (HEAs) 2. TRIP-assisted dual-phase HEAs 3. Interstitially alloyed TWIP-TRIP-HEAs 4. Summary and outlook 22

23 Motivation Possible solution: Adding interstitial atoms introducing interstitial solid solution (SS) strengthening Interstitial atoms: C, N, B ; Content: 0.2 at.% / 0.5 at.% / 0.8 at.% 23

24 Interstitial TWIP-TRIP-HEAs TRIP-DP-HEA + 0.5at%C Fe 49.5 Mn 30 Co 10 Cr 10 C 0.5 Casting Hot-rolling (50% / 900 C) Homogenization (2 h / 1200 C with Ar + Water quenching) Chemical analysis results (at. %): Alloy C Cr Co Ni Mn Fe FeMnCoCrC

25 Interstitial TWIP-TRIP-HEAs As-homogenized (1200 o C, 2h, water-quenched) CG C-HEA Z. Li, et al., Sci. Rep., (2017) 25

26 Interstitial TWIP-TRIP-HEAs ihea Grain-refined (Cold-rolled 70%; annealed at 900 o C/3 min, water-quenched) FG C-HEA Carbide: M 23 C 6 Element At.% Mn 17.82% Cr 47.16% Co 1.92% Fe 13.64% Metal 80.54% C 19.46% 50~100 nm, ~1.5 vol.% C in the Matrix: 0.35 at% Z. Li, et al., Sci. Rep., (2017) 26

27 Interstitial TWIP-TRIP-HEAs ihea Z. Li, et al., Sci. Rep., (2017) Ref. i: Li, Z. et al., Nature, 534, 227 (2016). Ref. ii: Otto, F. et al., Acta Mater. 61, 5743 (2013). 27

28 Interstitial TWIP-TRIP-HEAs ihea Z. Li, et al., Sci. Rep., (2017) 28

29 Interstitial TWIP-TRIP-HEAs ihea Z. Li, et al., Sci. Rep., (2017) 29

30 Interstitial TWIP-TRIP-HEAs ihea Z. Li, et al., Sci. Rep., (2017) 30

31 Outline 1. Background of high-entropy alloys (HEAs) 2. TRIP-assisted dual-phase HEAs 3. Interstitially alloyed TWIP-TRIP-HEAs 4. Summary and outlook 31

32 Summary 32

33 Outlook High-Entropy Alloys Group at MPIE New HEAs design New quinary TRIP-DP-HEAs Interstitial quinary TRIP-HEAs (Dr. Xiaoxiang Wu) Light-weight high-strength HEAs (Dr. Jing Su, Dr. Zhangwei Wang) High-temperature refractory HEAs (Mr. Yueling Guo) Functional (magnetic/thermal) HEAs (Mr. Ziyuan Rao) Further studies on current HEAs Hydrogen fracture behavior of HEAs (Dr. Hong Luo) Grain boundary segregations in HEAs (Dr. Linlin Li) High cyclic fatigue of HEAs (Dr. Xu Zhang) 33

34 Thanks for your attention! Zhiming Li, Dierk Raabe, Cem Tasan, Konda G. Pradeep, Yun Deng, Hauke Springer, Baptiste Gault, Fritz Körmann, Blazej Grabowski, Jörg Neugebauer, Hong Luo, Linlin Li, Jing Su, Xiaoxiang Wu, Zhangwei Wang, Xu Zhang, Wenjun Lu, Silva Basu