Application of Molecular Dynamics Calculations to Elucidation of the Mechanism of Hydrogen-Induced Crack Initiation in Fracture Toughness Tests Using Tempered Martensitic Steels
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引用次数: 0
Abstract
: It is well known that the presence of hydrogen deteriorates mechanical properties of steels, that appears as reduced fracture toughness, shorter fatigue lifetime, etc.; these phenomena are recognized as hydrogen embrittlement . The effect of hydrogen on crack initiation of fracture toughness test has been investigated using a combination of experimental and computational approaches. Tempered lath martensitic steel was subjected to fracture toughness test with monotonically rising load in air and high-pressure hydrogen gas. While crack propagated continuously within grains in air, cracking in hydrogen grew by linking isolated interface failure ahead of a main crack tip. Then, to understand the nucleation mechanism of isolated failure in the presence of hydrogen, the tensile simulations of twist grain boundaries (TGBs) rotated along <110> axis at various angles were conducted using molecular dynamics calculations. While the dislocation emission from TGB rotated 70° is dominant deformation mode in the absence of hydrogen, the rupture along TGB rotated 110° and 170° without stress relaxation due to dislocation emission is dominant deformation mode in the presence of hydrogen. As a consequence, it is indicated that the origin of hydrogen-induced isolated crack initiation in the vicinity of fatigue pre-crack is the rupture along the block boundaries within martensitic structure due to hydrogen-induced inhibition of dislocation emission from GBs.
期刊介绍:
The journal ISIJ International first appeared in 1961 under the title Tetsu-to-Hagané Overseas. The title was changed in 1966 to Transactions of The Iron and Steel Institute of Japan and again in 1989 to the current ISIJ International.
The journal provides an international medium for the publication of fundamental and technological aspects of the properties, structure, characterization and modeling, processing, fabrication, and environmental issues of iron and steel, along with related engineering materials.
Classification
I Fundamentals of High Temperature Processes
II Ironmaking
III Steelmaking
IV Casting and Solidification
V Instrumentation, Control, and System Engineering
VI Chemical and Physical Analysis
VII Forming Processing and Thermomechanical Treatment
VIII Welding and Joining
IX Surface Treatment and Corrosion
X Transformations and Microstructures
XI Mechanical Properties
XII Physical Properties
XIII New Materials and Processes
XIV Social and Environmental Engineering.