Kink-band formation in the directionally-solidified Mg/LPSO two-phase alloys

Toko Tokunaga; Koji Hagihara; Michiaki Yamasaki; Tsuyoshi Mayama; Kazuki Yamamoto; Hiroki Narimoto; Taiki Kida; Yoshihito Kawamura; Takayoshi Nakano

doi:10.1080/14686996.2022.2137696

Kink-band formation in the directionally-solidified Mg/LPSO two-phase alloys

Sci Technol Adv Mater. 2022 Nov 3;23(1):752-766. doi: 10.1080/14686996.2022.2137696. eCollection 2022.

Authors

Toko Tokunaga¹, Koji Hagihara^{1

2}, Michiaki Yamasaki³, Tsuyoshi Mayama³, Kazuki Yamamoto¹, Hiroki Narimoto⁴, Taiki Kida², Yoshihito Kawamura³, Takayoshi Nakano²

Affiliations

¹ Department of Physical Science and Engineering, Nagoya Institute of Technology, Nagoya, Aichi, Japan.
² Division of Materials and Manufacturing Science, Graduate School of Engineering, Suita, Osaka, Japan.
³ Magnesium Research Center & Department of Materials Science, Kumamoto University, Kumamoto, Japan.
⁴ Department of Adaptive Machine Systems, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.

Abstract

The variation in the mechanical properties with the volume fraction of the long-period stacking ordered (LPSO) phase in directionally solidified (DS) Mg/LPSO two-phase alloys was examined. Unexpectedly, the yield stress of the DS alloys increases non-monotonically with an increase in the volume fraction of the LPSO phase. The LPSO phase is considered an effective strengthening phase in Mg alloys, when the stress is applied parallel to the growth direction. Nevertheless, the highest strength was obtained in alloys with 61-86 vol.% of the LPSO phase, which was considerably higher than that in the LPSO single-phase alloy. It was clarified that this complicated variation in the yield stress was generated from the change in the formation stress of kink bands, which varied with the thickness of the LPSO-phase grains. Furthermore, the coexistence of Mg in the LPSO phase alloy induced the homogeneous formation of kink bands in the alloys, leading to the enhancement of the 'kink-band strengthening'. The results demonstrated that microstructural control is significantly important in Mg/LPSO two-phase alloys, in which both phases exhibit strong plastic anisotropy, to realize the maximum mechanical properties.

Keywords: LPSO-phase; Mg alloy; kink band; microstructure; strength.

Grants and funding

The work was supported by the Core Research for Evolutional Science and Technology [JPMJCR2094]; Iketani Science and Technology Foundation [0331020-A]; JSPS [JP18H05478, JP18H05476, JP18H05475, 21K18826 and JP18H05254].