Development of Novel 20Cr Ferritic Stainless Steels via Nanoscale G-Phase Dispersion Strengthening: A Brief Review

Abstract

Extensive investigations have revealed the precipitation of nanometer-scale silicides, identified as G-phase, within the ferritic matrix of duplex stainless steels during prolonged thermal aging. These silicides typically exhibit a well-defined coherent orientation relationship with the ferrite matrix, specifically (100_G//100_F, 110_G//110_F, 111_G//111_F). Consequently, the authors and their research team proposed a novel concept in 2015: utilizing the G-phase as a primary strengthening phase. It was proposed that through strategic alloy design, these silicides—ordinarily considered deleterious in duplex stainless steels—could be used to develop a new generation of dispersion-strengthened ferritic stainless steels. This approach aims to significantly enhance the yield strength of the alloy while maintaining excellent tensile ductility. Over the past decade, the authors and their research team have focused on nanoscale G-phase dispersion-strengthened ferritic stainless steels. By combining first-principles calculations with thermodynamic database-driven alloy design, a series of new ferritic stainless steel systems based on G-phase strengthening has been developed. These efforts have yielded extensive fundamental results regarding the compositional control, microstructural design, and mechanical properties of silicide-strengthened 20Cr ferritic stainless steels. Based on a comprehensive review of the existing literature, this paper further summarizes the compositional design criteria and microstructural control strategies for G-phase strengthened steels. It is hoped that this work will encourage further fundamental research and industrial applications in this field.

Keywords

Silicide G-phase / Ferritic stainless steels / Precipitation strengthening / Strength-ductility synergy

Acknowledgments

All authors gratefully acknowledge the assistance from Y. Qiu and D. He at SUStech Core Research Facilities and the electron microscope center of KAIPLE Co., Ltd. (Changsha, China) for the support of microstructural characterizations.

Author Contributions

M.Y.: Conceptualization, Methodology, Funding acquisition, Supervision, Literature review, Writing—original draft, Writing—review & editing. D.Z. (Daobin Zhang): Literature review, Writing—original draft. J.Y.: Funding acquisition, Literature review. Z.Y.: Methodology, Literature review. D.Z. (Dingding Zhu): Literature review, Writing—review & editing. B.D.: Literature review. M.H.: Funding acquisition, Literature review. S.W.: Literature review, Writing—review & editing. C.W.: Literature review, Writing—review & editing. X.L.: Conceptualization, Funding acquisition, Literature revie, Writing—review & editing.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

No new data were generated or analyzed in this study. All information is available within the cited references.

Funding

M.Y. acknowleges the support from the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2023A1515240048), the Shenzhen Science and Technology Program (Grant No. JCYJ20240813094806009) and the National Natural Science Foundation of China (Grant No. 52301153); J.Y. acknowleges the support from the National Natural Science Foundation of China (Grant No. 52301154) and the Shenzhen Science and Technology Program (Grant No. JCYJ20220530114400001); M.H. acknowleges the support from the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2023A1515110595); Z.Y. acknowleges the support from the National Natural Science Foundation of China (Grant No. 52301042) and the Natural Science Foundation of Top Talent of SZTU (grant No. GDRC202532).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

[1] Jiang S, Wang H, Wu Y, Liu X, Chen H, Yao M, et al. Ultrastrong steel via minimal lattice misfit and high—density nanoprecipitation. Nature 2017, 544, 460-464. DOI: 10.1038/nature22032

[2] He BB, Hu B, Yen HW, Cheng GJ, Wang ZK, Luo HW, et al. High dislocation density—induced large ductility in deformed and partitioned steels. Science 2017, 357, 1029-1032. DOI: 10.1126/science.aan0177

[3] Kwiatkowski da Silva A, Souza Filho IR, Lu W, Zilnyk KD, Hupalo MF, Alves LM, et al. A sustainable ultra—high strength Fe18Mn3Ti maraging steel through controlled solute segregation and α—Mn nanoprecipitation. Nat. Commun. 2022, 13, 2330. DOI: 10.1038/s41467—022—30019—x

[4] Gao J, Jiang S, Zhang H, Huang Y, Guan D, Xu Y, et al. Facile route to bulk ultrafine—grain steels for high strength and ductility. Nature 2021, 590, 262-267. DOI: 10.1038/s41586—021—03246—3

[5] Liu X, Liu C, Wu J, Zhang X, Zhu X, Wang J . Morphological instability of the G—phase induced a different contribution to hardening of ferrite phase in a duplex stainless steel. Mater. Sci. Eng. A 2022, 832, 142421. DOI: 10.1016/j.msea.2021.142421

[6] Mateo A, Llanes L, Anglada M, Redjaimia A, Metauer G . Characterization of the intermetallic G—phase in an AISI 329 duplex stainless steel. J. Mater. Sci. 1997, 32, 4533-4540. DOI: 10.1023/A:1018669217124

[7] Sun WW, Marceau RKW, Styles MJ, Barbier D, Hutchinson CR . G phase precipitation and strengthening in ultra—high strength ferritic steels: Towards lean ‘maraging’ metallurgy. Acta Mater. 2017, 130, 28-46. DOI: 10.1016/j.actamat.2017.03.032

[8] Zhang S, Shi X, Su Y, Yan W, Rong L, Yang K . G phase and ferrite in a high Si austenitic stainless steel during 510 °C aging. Mater. Charact. 2024, 207, 113587. DOI: 10.1016/j.matchar.2023.113587

[9] Zheng Y, Hu X, Jiang H, Song Y, Rong L . Precipitation behavior of G—phase and its effect on mechanical properties of 30Cr2Ni4MoV steel. Mater. Charact. 2025, 219, 114598. DOI: 10.1016/j.matchar.2024.114598

[10] Purzyńska H, Golański G, Zieliński A, Dobrzański JD, Sroka M . Precipitation study in Ti—stabilised austenitic stainless steel after 207,000 h of service. Mater. High Temp. 2019, 36, 296-303. DOI: 10.1080/09603409.2018.1546919

[11] Guo XF, Ni YY, Gong JM, Geng LY, Tang JQ, Jiang Y, et al. Formation of G—phase in 20Cr32Ni1Nb Stainless Steel and its Effect on Mechanical Properties. Acta Metall. Sin. 2017, 30, 829-839. DOI: 10.1007/s40195—017—0589—0

[12] Pedro Ibañez RA, de Almeida Soares GD, de Almeida LH, Le May I . Effects of Si content on the microstructure of modified—HP austenitic steels. Mater. Charact. 1993, 30, 243-249. DOI: 10.1016/1044—5803(93)90071—3

[13] Chen WY, Li M, Zhang X, Kirk MA, Baldo PM, Lian T . In situ TEM study of G—phase precipitates under heavy ion irradiation in CF8 cast austenitic stainless steel . J. Nucl. Mater. 2015, 464, 185-192. DOI: 10.1016/j.jnucmat.2015.04.042

[14] Lee EH, Maziasz PJ, Rowcliffe AF . Structure and Composition of Phases Occurring in Austenitic Stainless Steels in Thermal and Irradiation Environments: CONF—801072—11 ; Oak Ridge National Lab.: Oak Ridge, TN, USA, 1980.

[15] Porollo SI, Konobeev YV, Garner FА . Swelling and microstructure of austenitic stainless steel ChS—68 CW after high dose neutron irradiation. J. Nucl. Mater. 2009, 393, 61-66. DOI: 10.1016/j.jnucmat.2009.05.005

[16] Kong BS, Shin JH, Jang C, Na YE, Jang D, Lee HJ, et al. Effect of proton irradiation on δ—ferrite in the thermally aged austenitic stainless steel weld: Precipitation of G—phase and additional hardening. J. Nucl. Mater. 2021, 544, 152656. DOI: 10.1016/j.jnucmat.2020.152656

[17] Lin X, Peng Q, Han EH, Ke W, Jiao Z . Irradiation—induced precipitation and inverse coarsening of G—phase in austenitic stainless steel weld metal. Mater. Charact. 2019, 151, 396-403. DOI: 10.1016/j.matchar.2019.03.035

[18] Badyka R, Saillet S, Emo J, Domain C, Pareige C . Effect of Ni, Mo and Mn content on spinodal decomposition kinetics and G—phase precipitation of aged model cast austenitic stainless steels. J. Nucl. Mater. 2021, 555, 153123. DOI: 10.1016/j.jnucmat.2021.153123

[19] Gupta H, Kapoor R, Shinde D, Makineni SK . Achieving ultra—high flow stress and hardness in a medium Mn stainless steel by the formation of strain—induced martensite and G—phase precipitates. Scr. Mater. 2024, 241, 115892. DOI: 10.1016/j.scriptamat.2023.115892

[20] Gemperle A, Gemperlová J, Sha W, Smith GDW . Aging behaviour of cobalt free chromium containing maraging steels. Mater. Sci. Technol. 1992, 8, 546-554. DOI: 10.1179/mst.1992.8.6.546

[21] Sha W, Cerezo A, Smith GDW . Phase chemistry and precipitation reactions in maraging steels: Part III. Model alloys. Met. Trans. A 1993, 24, 1241-1249. DOI: 10.1007/BF02668192

[22] Murayama M, Hono K, Katayama Y . Microstructural evolution in a 17—4 PH stainless steel after aging at 400 °C. Met. Mater. Trans. A 1999, 30, 345-353. DOI: 10.1007/s11661—999—0323—2

[23] Schober M, Schnitzer R, Leitner H . Precipitation evolution in a Ti—free and Ti—containing stainless maraging steel. Ultramicroscopy 2009, 109, 553-562. DOI: 10.1016/j.ultramic.2008.10.016

[24] Schnitzer R, Schober M, Zinner S, Leitner H . Effect of Cu on the evolution of precipitation in an Fe—Cr—Ni—Al—Ti maraging steel. Acta Mater. 2010, 58, 3733-3741. DOI: 10.1016/j.actamat.2010.03.010

[25] Leitner H, Schnitzer R, Schober M, Zinner S . Precipitate modification in PH13—8 Mo type maraging steel. Acta Mater. 2011, 59, 5012-5022. DOI: 10.1016/j.actamat.2011.04.053

[26] Staron P, Jamnig B, Leitner H, Ebner R, Clemens H . Small—angle neutron scattering analysis of the precipitation behaviour in a maraging steel. J. Appl. Crystallogr. 2003, 36, 415-419. DOI: 10.1107/S0021889803000293

[27] Jamnig B, Ebner R, Staron P, Clemens H, Leitner H, Jeglitsch F, et al. On the Precipitation Behaviour in Maraging Steels. In Proceedings of the 6th International Tooling Conference, Karlstad, Sweden, 10—13 September 2002.

[28] Guo Z, Sha W . Comments on Small—angle neutron scattering analysis of the precipitation behaviour in a maraging steel by Staron, Jamnig, Leitner, Ebner & Clemens (2003) . J. Appl. Crystallogr. 2004, 37, 325-326. DOI: 10.1107/S0021889803028127

[29] Leitner H, Schober M, Schnitzer R, Zinner S . Strengthening behavior of Fe—Cr—Ni—Al—(Ti) maraging steels. Mater. Sci. Eng. A 2011, 528, 5264-5270. DOI: 10.1016/j.msea.2011.03.058

[30] Chen Y, Dai X, Chen X, Yang B . The characterization of G—phase in Fe20Cr9Ni cast duplex stainless steel. Mater. Charact. 2019, 149, 74-81. DOI: 10.1016/j.matchar.2019.01.012

[31] Hamaoka T, Nomoto A, Nishida K, Dohi K, Soneda N . Accurate determination of the number density of G—phase precipitates in thermally aged duplex stainless steel. Philos. Mag. 2012, 92, 2716-2732. DOI: 10.1080/14786435.2012.674222

[32] Hamaoka T, Nomoto A, Nishida K, Dohi K, Soneda N . Effects of aging temperature on G—phase precipitation and ferrite—phase decomposition in duplex stainless steel. Philos. Mag. 2012, 92, 4354-4375. DOI: 10.1080/14786435.2012.707340

[33] Pareige C, Novy S, Saillet S, Pareige P . Study of phase transformation and mechanical properties evolution of duplex stainless steels after long term thermal ageing (>20 years). J. Nucl. Mater. 2011, 411, 90-96. DOI: 10.1016/j.jnucmat.2011.01.036

[34] Li S, Wang Y, Wang X, Xue F . G—phase precipitation in duplex stainless steels after long—term thermal aging: A high—resolution transmission electron microscopy study. J. Nucl. Mater. 2014, 452, 382-388. DOI: 10.1016/j.jnucmat.2014.05.069

[35] Badyka R, Monnet G, Saillet S, Domain C, Pareige C . Quantification of hardening contribution of G—Phase precipitation and spinodal decomposition in aged duplex stainless steel: APT analysis and micro—hardness measurements. J. Nucl. Mater. 2019, 514, 266-275. DOI: 10.1016/j.jnucmat.2018.12.002

[36] Guo W, Garfinkel DA, Tucker JD, Haley D, Young GA, Poplawsky JD . An atom probe perspective on phase separation and precipitation in duplex stainless steels. Nanotechnology 2016, 27, 254004. DOI: 10.1088/0957—4484/27/25/254004

[37] Garfinkel DA, Poplawsky JD, Guo W, Young GA, Tucker JD . Phase Separation in Lean—Grade Duplex Stainless Steel 2101. JOM 2015, 67, 2216-2222. DOI: 10.1007/s11837—015—1581—7

[38] Pareige C, Emo J, Saillet S, Domain C, Pareige P . Kinetics of G—phase precipitation and spinodal decomposition in very long aged ferrite of a Mo—free duplex stainless steel. J. Nucl. Mater. 2015, 465, 383-389. DOI: 10.1016/j.jnucmat.2015.06.017

[39] Zhang B, Xue F, Li SL, Wang XT, Liang NN, Zhao YH, et al. Non—uniform phase separation in ferrite of a duplex stainless steel. Acta Mater. 2017, 140, 388-397. DOI: 10.1016/j.actamat.2017.08.044

[40] Yuan Y, Xie Y, Hou Z, Jin Q, Ke Y, Dong Z, et al. Synergistic effect of dislocation and elemental clustering on spinodal decomposition in super duplex stainless steel. Mater. Charact. 2025, 221, 114719. DOI: 10.1016/j.matchar.2025.114719

[41] Chen Y, Yang B, Zhou Y, Wu Y, Zhu H . Evaluation of pitting corrosion in duplex stainless steel Fe20Cr9Ni for nuclear power application. Acta Mater. 2020, 197, 172-183. DOI: 10.1016/j.actamat.2020.07.046

[42] Xia Z, Liu W, Li Y, Liu B, Qiu W, Xiong Y, et al. Effect of G—phase and heterogeneous deformation—induced strengthening on the mechanical properties of Cu—20Ni—20Mn—2Fe—1Si alloy. Mater. Charact. 2023, 205, 113325. DOI: 10.1016/j.matchar.2023.113325

[43] Dong H, Zhong R, Liu L, Wang Z, Yang C, Luo Z, et al. The intergranular precipitation behavior of G phase in a high—performance complex cast Cu—Ni—Al alloy. Mater. Charact. 2023, 196, 112611. DOI: 10.1016/j.matchar.2022.112611

[44] Jeong HW, Shin JY, Kwon SH, Kato H, Choi EA, Han SZ . Silicon effects on the formation of heterogeneous intermetallic compound phases in Cu—Ni—Si(—Mn) alloys under homogenization treatment. Intermetallics 2025, 185, 108913. DOI: 10.1016/j.intermet.2025.108913

[45] Zhang X, Li S, Liu Q, Zhao D, Zhang X, Wu P, et al. The effect of Sr on the microstructure and properties of Ni—Ti—Si type G—phase reinforced copper alloy. Intermetallics 2026, 192, 109245. DOI: 10.1016/j.intermet.2026.109245

[46] Zhang X, Liu Q, Zhao D, Liu Y, Hua S, Ding H . Growth and evolution of Ni—Ti—Si type G phase Ni₁₆Ti₆Si₇ in Cu alloys . Mater. Charact. 2024, 216, 114304. DOI: 10.1016/j.matchar.2024.114304

[47] Yang M, Wang C, Yang S, Shi Z, Liu X . New insights into the precipitation strengthening of ferritic steels: Nanoscale G—phase particle. Mater. Lett. 2017, 209, 134-137. DOI: 10.1016/j.matlet.2017.07.078

[48] Yang M, Zhu J, Wu C, Yang S, Shi Z, Wang C, et al. Microstructural evolution and precipitation strengthening in a new 20Cr ferritic trial steel. Mater. Sci. Eng. A 2019, 742, 734-742. DOI: 10.1016/j.msea.2018.05.027

[49] Yang M, Zhu J, Yang T, Luan J, Jiao Z, Fan X, et al. A novel ferritic steel family hardened by intermetallic compound G—phase. Mater. Sci. Eng. A 2019, 745, 390-399. DOI: 10.1016/j.msea.2018.11.148

[50] Yang M, King DJM, Povstugar I, Wen Y, Luan J, Kuhn B, et al. Precipitation behavior in G—phase strengthened ferritic stainless steels. Acta Mater. 2021, 205, 116542. DOI: 10.1016/j.actamat.2020.116542

[51] Yang M. Alloy Design, Aging Behavior and Mechanical Properties of the G—Phase Strengthened Fe—Ni—Si—Based BCC Structural Steels. Ph.D. Thesis, Xiamen University, Xiamen, China, 2019.

[52] Wang CP, Hu Y, Yang SY, Lu Y, Jiang QW, Liu XJ . Experimental Investigation of Phase Equilibria in the Fe—Si—Zr Ternary System. J. Phase Equilib. Diffus. 2013, 34, 277-288. DOI: 10.1007/s11669—013—0242—1

[53] Hu X, Chen G, Ion C, Ni K . The 1100 °C isothermal section of the Ti—Ni—Si ternary system. J. Phase Equilibria 1999, 20, 508-514. DOI: 10.1361/105497199770340761

[54] Wang C, Huang X, Huang L, Yang M, Yang P, Cui Y, et al. Experimental Investigation of Phase Equilibria in the Co—Ta—Si Ternary System. Materials 2022, 15, 3097. DOI: 10.3390/ma15093097

[55] Wang C, Huang X, Yang M, Han J, Yao Z, Yang T, et al. Development of novel ferritic steels strengthened by the Co16X6Si7—G phase: A theoretical and experimental study. Mater. Des. 2022, 222, 111021. DOI: 10.1016/j.matdes.2022.111021

[56] King DJM, Yang M, Whiting TM, Liu X, Wenman MR . G—phase strengthened iron alloys by design. Acta Mater. 2020, 183, 350-361. DOI: 10.1016/j.actamat.2019.11.007

[57] Beattie HJ, Versnyder FL . A New Complex Phase in a High—Temperature Alloy. Nature 1956, 178, 208-209. DOI: 10.1038/178208b0

[58] Yang M, Huang C, Han J, Wu H, Zhao Y, Yang T, et al. Development of the high—strength ductile ferritic alloys via regulating the intragranular and grain boundary precipitation of G—phase. J. Mater. Sci. Technol. 2023, 136, 180-199. DOI: 10.1016/j.jmst.2022.07.029

[59] Bochenek K, Rogal Ł, Jarząbek D, Włoczewski M, Rygier T, Jenczyk P, et al. Rhenium—induced strengthening and microstructural stability in hot—pressed AlCoCrFeNi dual—phase high—entropy alloy. Arch. Civ. Mech. Eng. 2026, 26, 115. DOI: 10.1007/s43452—026—01499—1

[60] Turnali A, Hariharan A, Polatidis E, Peter NJ, Gehlmann J, Sofras C, et al. Harnessing additive manufacturing—induced microstructure and solute heterogeneities for the design of precipitation—strengthened alloys. Acta Mater. 2025, 298, 121423. DOI: 10.1016/j.actamat.2025.121423

[61] Ma K, Ferreirós PA, Pfeifer TW, Abernethy RG, von Tiedemann S, Peng N, et al. Intermetallic dispersion—strengthened ferritic superalloys with exceptional resistance to radiation—induced hardening. Acta Mater. 2025, 293, 121095. DOI: 10.1016/j.actamat.2025.121095

[62] Shen Z, Qiu N, Zhao L, Liang Z, Zuo X . Effects of Co—precipitation on local stacking fault energy modulation and Strength—Ductility synergy in Fe—Mn—Ni—Al—Cu—V—C austenitic steels. Mater. Sci. Eng. A 2026, 950, 149515. DOI: 10.1016/j.msea.2025.149515

[63] Liu Y, Pang X, He S, Zhang L, Lin Z, Du P, et al. In—situ formation of AlN nanoparticles in NiAl—strengthened ferritic alloy with enhanced high—temperature mechanical properties via SLM fabrication. Mater. Sci. Eng. A 2024, 899, 146460. DOI: 10.1016/j.msea.2024.146460

[64] Jiao ZB, Luan JH, Miller MK, Yu CY, Liu CT . Effects of Mn partitioning on nanoscale precipitation and mechanical properties of ferritic steels strengthened by NiAl nanoparticles. Acta Mater. 2015, 84, 283-291. DOI: 10.1016/j.actamat.2014.10.065

[65] Włoczewski M, Jasiewicz K, Jenczyk P, Gadalińska E, Kulikowski K, Zhang Y, et al. AlCoCrFeNiTi_0.2 High—Entropy Alloy Under Plasma Nitriding: Complex Microstructure Transformation, Mechanical and Tribological Enhancement . Met. Mater. Trans. A 2025, 56, 2040-2056. DOI: 10.1007/s11661—025—07752—1