◆ Environmentally-assisted fracture problem
・Hydrogen embrittlement
The mechanical properties of metallic materials are influenced by the
surrounding environment. Particularly, ductility and toughness are significantly
reduced when hydrogen is absorbed, which is know as hydrogen embrittlement
(HE). From a microscopic viewpoint, grain boundaries (GBs) tends to be
a typical fracture site when HE is promoted. The susceptibility of GBs
to HE then needs to be studied in detail.
We successfully evaluated for the first time the HE property of a discrete
GB by utilizing our micromechanical testing method (see micro-materials fracture problem). By comparing samples taken from different GBs, it was found that HE
susceptibility depends both on orientation difference and GB type.
For more detail, see:
Y. Takahashi, H. Kondo, R. Asano, S. Arai, K. Higuchi, Y. Yamamoto, S.
Muto, N. Tanaka, Direct evaluation of grain boundary hydrogen embrittlement:
a micro-mechanical approach, Materials Science & Engineering A, Vol.
661, 2016, pp. 211–216 (http://dx.doi.org/10.1016/j.msea.2016.03.035).
Related studies:
Y. Takahashi, I. Ashida, S. Arai, K. Higuchi, Y. Yamamoto, S. Muto, Interfacial
fracture strength evaluation of Cu/SiN micro-components: applicability
of the linear fracture mechanics criterion under a hydrogen environment,
International Journal of Fracture, Vol. 210, 2018, pp. 223–231 (https://doi.org/10.1007/s10704-018-0269-8)
Y. Takahashi, K. Yamaguchi, M. Tanaka, K. Higashida, H. Noguchi, On the
micro-mechanism of hydrogen-assisted cracking in a single-crystalline iron-silicon
alloy thin sheet, Scripta Materialia, Vol. 64, 2011, pp. 537–540 (https://doi.org/10.1016/j.scriptamat.2010.11.035)
Y. Takahashi, M. Tanaka, K. Higashida, K. Yamaguchi, H. Noguchi, An intrinsic
effect of hydrogen on cyclic slip deformation around a {110} fatigue crack
in Fe-3.2 wt.% Si alloy, Acta Materialia, Vol. 58, 2010, pp. 1972–1981
(https://doi.org/10.1016/j.actamat.2009.11.040)
・Fracture at elevated temprature