9:15 AM - 9:30 AM
[SCG49-08] Experimental investigation on kink strengthening of single crystal biotite
Keywords:kinkband
1. Introduction
In material science, it has been pointed out that the kink formation in mille-feuille structure may cause kink strengthening, which can be strengthened beyond the intrinsic strength of the material [1, 2, 3]. In a previous study [4], it is reported that shear occurs on a limited slip surface in the long-period stacking-ordered (LPSO) structure and deformations that satisfy the rank-1 connection result in forming kink bands. In an analog experiment of kink formation in layered rocks [5], it was shown that strain hardening occurs with kink formation. However, it is not clear whether similar kink strengthening occurs in actual rocks. It is also unclear whether kink formation in rocks is caused by shearing on limited slip surfaces, similar to LPSO structure. Therefore, in this study, we conducted deformation experiments on biotite single crystals which is a layered mineral that plays an important role in the strength of the crust, and investigated kink formation and kink strengthening by observing stress strain behavior and microstructures.
2. Methods
We used the high-pressure high-temperature gas apparatus installed at Tohoku University. The conditions on the experiments were chosen as follows in the order of temperature(℃), confining pressure(MPa), crystal orientation: 1). 300℃, 10MPa, [010], 2). 300℃, 100MPa, [010], 3). 600℃, 100MPa, [100], 4). 600℃, 100MPa, 45°to [001], and 5). 300℃, 185MPa, [010]. Note that all samples were compressed parallel to the above orientation. In addition, we observed microstructures of samples deformed at the conditions 300℃, 10MPa, [010], 300℃, 185MPa, [010] using scanning electron microscope (SEM).
3. Results and Discussion
We observed strain hardening occurred immediately after yielding from stress-strain curves of each experiment. As the confining pressure increased from 10 MPa to 100 MPa and 185 MPa, both the yield and final stresses increase while the stress decrease with temperatures. Microstructural investigation revealed the formation of kink bands in both samples deformed under 300℃, 10MPa, [010] and 300℃, 185MPa, [010] conditions. We further observed that the matrix phase was rotated by kink formation, when comparing the kink band orientation and the stress field following a previous study [6]. Since the axial compression was done parallel to the basal plane of biotite in this experiment, the matrix phase should be parallel to the maximum compressive stress after kink band formation [6]. However, the crystal was rotated. This indicate that the mechanism which kink bands form in LPSO structure by satisfying the rank-1 connection may apply to biotite as well. A previous study [6] states that yielding and kink formation are likely to occur in the part of the foliated structure with a slight initial gradient of the slip plane, so the result indicates that the initial gradient of the slip plane may cause shear and kink band formation occur by a mechanism similar to that of the LPSO structure. In future investigations, we will conduct microstructural analysis of samples prior to deformation and observe how much a slight initial gradient of the slip plane contribute to kink formation. In addition, we need to understand how kink strengthening, as it is known in material science, does affect the strength of lithosphere.
References
[1] Hagihara, K., Ueyama, R., Tokunaga, T., Yamasaki, M., Kawamura,Y., Nakano, T. 2021, Materials Research Letters, 9:11, 467-474.
[2] Hagiharaa, K., Yamasakib, M., Kawamurab, Y., Nakano, T. 2019, Materials Science & Engineering A 763, 138163.
[3] Hagihara, K., Ueyama, R., Yamasaki, M., Kawamura, Y., Nakano, T. 2021, Acta Materialia 209,116797
[4] Inamura, T. 2019, Acta Materialia 173, 270-280.
[5] Weiss, L. E. 1968, Geol. Surv. Canada Paper 68-52, 294-357.
[6] Uemura, T., Long , X. 1978, J. Geol. Soc. Jpn, 93, 681-699.
In material science, it has been pointed out that the kink formation in mille-feuille structure may cause kink strengthening, which can be strengthened beyond the intrinsic strength of the material [1, 2, 3]. In a previous study [4], it is reported that shear occurs on a limited slip surface in the long-period stacking-ordered (LPSO) structure and deformations that satisfy the rank-1 connection result in forming kink bands. In an analog experiment of kink formation in layered rocks [5], it was shown that strain hardening occurs with kink formation. However, it is not clear whether similar kink strengthening occurs in actual rocks. It is also unclear whether kink formation in rocks is caused by shearing on limited slip surfaces, similar to LPSO structure. Therefore, in this study, we conducted deformation experiments on biotite single crystals which is a layered mineral that plays an important role in the strength of the crust, and investigated kink formation and kink strengthening by observing stress strain behavior and microstructures.
2. Methods
We used the high-pressure high-temperature gas apparatus installed at Tohoku University. The conditions on the experiments were chosen as follows in the order of temperature(℃), confining pressure(MPa), crystal orientation: 1). 300℃, 10MPa, [010], 2). 300℃, 100MPa, [010], 3). 600℃, 100MPa, [100], 4). 600℃, 100MPa, 45°to [001], and 5). 300℃, 185MPa, [010]. Note that all samples were compressed parallel to the above orientation. In addition, we observed microstructures of samples deformed at the conditions 300℃, 10MPa, [010], 300℃, 185MPa, [010] using scanning electron microscope (SEM).
3. Results and Discussion
We observed strain hardening occurred immediately after yielding from stress-strain curves of each experiment. As the confining pressure increased from 10 MPa to 100 MPa and 185 MPa, both the yield and final stresses increase while the stress decrease with temperatures. Microstructural investigation revealed the formation of kink bands in both samples deformed under 300℃, 10MPa, [010] and 300℃, 185MPa, [010] conditions. We further observed that the matrix phase was rotated by kink formation, when comparing the kink band orientation and the stress field following a previous study [6]. Since the axial compression was done parallel to the basal plane of biotite in this experiment, the matrix phase should be parallel to the maximum compressive stress after kink band formation [6]. However, the crystal was rotated. This indicate that the mechanism which kink bands form in LPSO structure by satisfying the rank-1 connection may apply to biotite as well. A previous study [6] states that yielding and kink formation are likely to occur in the part of the foliated structure with a slight initial gradient of the slip plane, so the result indicates that the initial gradient of the slip plane may cause shear and kink band formation occur by a mechanism similar to that of the LPSO structure. In future investigations, we will conduct microstructural analysis of samples prior to deformation and observe how much a slight initial gradient of the slip plane contribute to kink formation. In addition, we need to understand how kink strengthening, as it is known in material science, does affect the strength of lithosphere.
References
[1] Hagihara, K., Ueyama, R., Tokunaga, T., Yamasaki, M., Kawamura,Y., Nakano, T. 2021, Materials Research Letters, 9:11, 467-474.
[2] Hagiharaa, K., Yamasakib, M., Kawamurab, Y., Nakano, T. 2019, Materials Science & Engineering A 763, 138163.
[3] Hagihara, K., Ueyama, R., Yamasaki, M., Kawamura, Y., Nakano, T. 2021, Acta Materialia 209,116797
[4] Inamura, T. 2019, Acta Materialia 173, 270-280.
[5] Weiss, L. E. 1968, Geol. Surv. Canada Paper 68-52, 294-357.
[6] Uemura, T., Long , X. 1978, J. Geol. Soc. Jpn, 93, 681-699.