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Abstract

The forming limit of AZ31 alloy, a representative Mg-Al-Zn-based wrought alloy, and the effect of severe plastic deformation (SPD) by examining the microstructure change caused by dynamic recrystallization led by high temperature and high dislocation density at 300℃ using a biaxial alternate forging (BAF) were investigated in this study. As a result of BAF test for AZ31 Mg alloy, significant cracks on the ends of workpieces occurred after 7 passes. The microstructure of as-extruded specimen showed the non-uniform distribution of the relatively coarse grains and the fine grains considered to be sub-grains. However, as the number of passes increases, the area of coarse grains gradually disappeared and the fine grains became more dominant in the microstructures. The result of tensile test for workpieces with each forging pass showed an increase in strength depending on pass number was shown with a slight increase of elongation. The Electron Backscatter Diffraction (EBSD) results exhibited that, the microstructure showed the presence of coarse grains and twins after only 1 pass, while the grains appeared to be significantly refined and uniformly distributed after 3 pass, at which the strength and elongation began to increase, simultaneously.
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Authors and Affiliations

Young-Chul Shin
1
ORCID: ORCID
Seong-Ho Ha
1
ORCID: ORCID
Abdul Wahid Shah
1
ORCID: ORCID

  1. Korea Institute of Industrial Technology (KITECH), Molding & Metal Forming R&D Department, 156 Gaetbeol-ro, Yeonsu-gu, Incheon 21999, Republic of Korea
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Abstract

Effect of Cu addition on oxide growth of Al-7 mass%Mg alloy at high temperature was investigated. As-cast microstructures of Al-7 mass%Mg and Al-7 mass%Mg-1 mass%Cu alloys showed α-Al dendrites and area of secondary particles. The 1 mass%Cu addition into Al-7 mass%Mg alloy formed Mg32(Al, Cu)49 ternary phase with β-Al3Mg2. The total fraction of two Mg-containing phases in Cu-added alloy was higher than the β-Al3Mg2 fraction in Cu-free alloy. From measured weight gains depending on time at 500°C under an air atmosphere, it was shown that all samples exhibited significant weight gains depending on time. Al-7mass%Mg-1mass%Cu alloy showed the relatively increased oxidation rate when compared with Cu-free alloy. All the oxidized cross-sections throughout the entire oxidation time showed coarse and dark areas regarded as oxides grown from the surface to inside, but bigger oxidized areas were formed in the Al-7mass%Mg-1mass%Cu alloy containing higher fraction of Mg-based phases in the as-cast microstructure. As a result of compositional analysis on the oxide clusters, it was found that the oxide clusters contained Mg-based oxides formed through internal oxidation during a long time exposure to oxidizing environments.
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Bibliography

[1] J.R. Davis, ASM International, Aluminum and Aluminum Alloys, Materials Park 1993.
[2] H. Watanabe, K. Ohori, Y. Takeuchi, Trans. Iron Steel Inst. Jpn. 27, 730 (1987).
[3] J.L. García-Hernández, C.G. Garay-Reyes, I.K. Gómez-Barraza, M.A. Ruiz-Esparza-Rodríguez, E.J. Gutiérrez-Castañeda, I. Estrada-Guel, M.C. Maldonado-Orozco, R. Martínez-Sánchez, J. Mater. Res. Technol. 8 (6), 5471 (2019).
[4] M . Mihara, C.D. Marioara, S.J. Andersen, R. Holmestad, E. Kobayashi, T. Sato, Mater. Sci. Eng. A, 658, 91 (2016).
[5] S.H. Ha, B.H. Kim, Y.O. Yoon, H.K. Lim, T.W. Lee, S.H. Lim, S.K. Kim, Int. J. Metalcast. 13, 121 (2019).
[6] G. Wu, K. Dash, M.L. Galano, K.A.Q. O’Reilly, Corros. Sci. 155, 97 (2019).
[7] B.H. Kim, S.H. Ha, Y.O. Yoon, H.K. Lim, S.K. Kim, D.H. Kim, Mater. Lett. 228, 108 (2018).
[8] H. Okamoto, J. Phase Equilibria 19, 598 (1998).
[9] T.S. Parel, S.C. Wang, M. J. Starink, Mater. Des. 31, S2 (2010).
[10] C.W. Bale, E. Bélisle, P. Chartrand, S.A. Decterov, G. Eriksson, A.E. Gheribi, K. Hack, I.H. Jung, Y.B. Kang, J. Melançon, A.D. Pelton, S. Petersen, C. Robelin, J. Sangster, P. Spencer, M.A. Van Ende, Calphad 54, 35 (2016).
[11] S.H. Ha, B.H. Kim, Y.O. Yoon, H.K. Lim, T.W. Lee, S.H. Lim, S.K. Kim, Sci. Adv. Mater. 10, 697 (2018).
[12] D . Ajmera, E. Panda, Corros. Sci. 102, 425 (2016).
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Authors and Affiliations

Seong-Ho Ha
1
ORCID: ORCID
Abdul Wahid Shah
1
ORCID: ORCID
Bong-Hwan Kim
1
ORCID: ORCID
Young-Ok Yoon
1
ORCID: ORCID
Hyun-Kyu Lim
1
ORCID: ORCID
Shae K. Kim
1
ORCID: ORCID

  1. Korea Institute of Industrial Technology (KITECH), Advanced Materials and Process R&D Department, Incheon 21999, Republic of Korea
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Abstract

Influence of Si addition on oxide layer growth of Al-6 mass%Mg alloys in molten state was investigated in this study. After melt holding for 24 h, the melt surface of only Si-free alloy became significantly bumpy, while no considerably oxidized surface was observed even with 1 mass%Si addition. There was no visible change on the appearance of melt surfaces with increasing Si content. As a result of compositional analysis on the melt samples between before and after melt holding, the Si-added alloys nearly maintained their Mg contents even after the melt holding for 24 h. On the other hand, the Mg content in the Si-free alloy showed a great reduction. The bumpy surface on Si-free alloy melt showed a large amount of pores and oxide clusters in its cross-section, while the Si-added alloy had no significantly grown oxide clusters on the surfaces. As a result of compositional analysis on the surfaces, the oxide clusters in Si-free alloy contained a great amount of Mg and oxygen. The oxide layer on the Si-added alloy was divided into Mg-rich and Mg-poor areas and contained certain amounts of Si. Such a mixed oxide layer containing Si would act as a protective layer during the melt holding for a long duration.
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Bibliography

[1] J.R. Davis, ASM International, Aluminum and Aluminum Alloys, Materials Park 1993.
[2] G . Wu, K. Dash, M.L. Galano, K.A.Q. O’Reilly, Corros. Sci. 155, 97 (2019).
[3] B.H. Kim, S.H. Ha, Y.O. Yoon, H.K. Lim, S.K. Kim, D.H. Kim, Mater. Lett. 228, 108 (2018).
[4] S.H. Ha, B.H. Kim, Y.O. Yoon, H.K. Lim, T.W. Lee, S.H. Lim, S.K. Kim, Sci. Adv. Mater. 10, 697 (2018).
[5] D . Ajmera, E. Panda, Corros. Sci. 102, 425 (2016).
[6] N. Smith, A. Kvithyld, G. Tranell, Metall. Mater. Trans. B 49, 2846 (2018).
[7] S.H. Ha, B.H. Kim, Y.O. Yoon, H.K. Lim, T.W. Lee, S.H. Lim, S.K. Kim, Int. J. Metalcast. 13, 121 (2019).
[8] J. Jeong, J. Im, K. Song, M. Kwon, S.K. Kim, Y.B. Kang, S.H. Oh, Acta Mater. 61, 3267 (2013).
[9] F . Zarei, H. Nuranian, K. Shirvani, Surf. Coat. Technol. 394, 125901 (2020).
[10] Y.L. Zhang, J. Li, Y.Y. Zhang, D.N. Kang, J. Alloys Compd. 827, 154131 (2020).
[11] W. Kai, P.C. Kao, P.C. Lin, I.F. Ren, J.S.C. Jang, Intermetallics 18, 1994 (2010).
[12] S.H. Ha, B.H. Kim, Y.O. Yoon, H.K. Lim, S.K. Kim, Sci. Adv. Mater. 10, 694 (2018).
[13] C.W. Bale, E. Bélisle, P. Chartrand, S.A. Decterov, G. Eriksson, A.E. Gheribi, K. Hack, I.H. Jung, Y.B. Kang, J. Melançon, A.D. Pelton, S. Petersen, C. Robelin, J. Sangster, P. Spencer, M.A. Van Ende, Calphad 54, 35 (2016).
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Authors and Affiliations

Young-Ok Yoon
1
ORCID: ORCID
Seong-Ho Ha
1
ORCID: ORCID
Abdul Wahid Shah
1
ORCID: ORCID
Bong-Hwan Kim
1
ORCID: ORCID
Hyun-Kyu Lim
1
ORCID: ORCID
Shae K. Kim
1
ORCID: ORCID

  1. Korea Institute of Industrial Technology (KITECH), Advanced Materials and Process R&D Department, Incheon 21999, Republic of Korea

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