Hydrogen-assisted stable crack growth in iron-3 wt% silicon steel

Journal Article · Thu Aug 01 00:00:00 EDT 1996 · Acta Materialia

DOI:https://doi.org/10.1016/1359-6454(95)00429-7· OSTI ID:367321

Marrow, T J; Prangnell, P ^[1]; Aindow, M; Strangwood, M; Knott, J F ^[2]

---

1. Univ. of Manchester and UMIST (United Kingdom). Manchester Materials Science Centre
2. Univ. of Birmingham (United Kingdom). School of Metallurgy and Materials

Observations of internal hydrogen cleavage in Fe-3Si are reported. Hydrogen-assisted stable crack growth (H-SCG) is associated with cleavage striations of a 300 nm spacing, observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM). High resolution SEM revealed finer striations, previously undetected, with a spacing of approximately 30 nm. These were parallel to the coarser striations. Scanning tunneling microscopy (STM) also showed the fine striation spacing, and gave a striation height of approximately 15 nm. The crack front was not parallel to the striations. Transmission electron microscopy (TEM) of crack tip plastic zones showed {l_brace}112{r_brace} and {l_brace}110{r_brace} slip, with a high dislocation density (around 10{sup 14}m{sup {minus}2}). The slip plane spacing was approximately 15--30 nm. Parallel arrays of high dislocation density were observed in the wake of the hydrogen cleavage crack. It is concluded that H-ScG in Fe-3Si occurs by periodic brittle cleavage on the {l_brace}001{r_brace} planes. This is preceded by dislocation emission. The coarse striations are produced by crack tip blunting and the fine striations by dislocations attracted by image forces to the fracture surface after cleavage. The effects of temperature, pressure and yield strength on the kinetics of H-SCG can be predicted using a model for diffusion of hydrogen through the plastic zone.

• OSTI ID: 367321
• Journal Information: Acta Materialia, Vol. 44, Issue 8; Other Information: PBD: Aug 1996
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
IRON BASE ALLOYS
FRACTURE PROPERTIES
SILICON ALLOYS
HYDROGEN
METALLURGICAL EFFECTS
CRACKS
CLEAVAGE
STRIATIONS
SCANNING ELECTRON MICROSCOPY
TRANSMISSION ELECTRON MICROSCOPY
SLIP
DISLOCATIONS
KINETICS
TEMPERATURE DEPENDENCE
PRESSURE DEPENDENCE
YIELD STRENGTH
MATHEMATICAL MODELS
DIFFUSION