Role of small-angle (subgrain boundary) and large-angle (grain boundary) interfaces on 5- and 3-power-law creep

1993 ◽  
Vol 166 (1-2) ◽  
pp. 81-88 ◽  
Author(s):  
M.E. Kassner
Keyword(s):  
Grain Boundary ◽  
Power Law ◽  
Small Angle ◽  
Subgrain Boundary ◽  
Large Angle ◽  
Power Law Creep

scholarly journals Effect of Heat Treatment on Microstructure and Properties of 24CrNiMo Alloy Steel Formed by Selective Laser Melting (SLM)

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 631
Author(s):  
Yongsheng Zhao ◽  
Chenggang Ding
Keyword(s):  
Grain Boundary ◽  
Alloy Steel ◽  
Thermal Fatigue ◽  
Small Angle ◽  
Friction And Wear ◽  
Large Angle ◽  
Granular Bainite ◽  
Face Centered Cubic ◽  
Wear Properties ◽  
Thermal Fatigue Crack

The 24CrNiMo alloy steel powder was used as experimental material. The microstructure and mechanical properties of as-deposited, quenched and tempered (QT) and stress-relief annealed (SR) specimens were analyzed. The X-ray diffraction (XRD) analysis showed that the specimens in the three states were mainly ferrite (α-Fe), in which the as-deposited samples had puny face-centered cubic (FCC) structure Fe (γ-Fe). The microstructure observation showed that the as-deposited specimens were made up of ferrite, granular bainite, a small amount of cementite and residual austenite. The tensile test results indicated that the tensile strength and yield strength of the as-deposited specimens were 1199 MPa and 1053 MPa respectively, and the elongation at break was 10.7%. The elongation of QT and SR specimens increased to 11.6% and 12.8%, respectively. The electron backscattered scattering detection (EBSD) analysis results showed that the small-angle grain boundary content of the as-deposited samples was 58%, and large-angle grain boundary content was 15%. After QT and SR, small-angle and large-angle grain boundaries were obtained than those in the as-deposited specimens. The high-temperature friction and wear properties and thermal fatigue performances of the QT and SR specimens were improved significantly. The QT specimens had the smallest wear and thermal fatigue crack lengths, excellent resistance to friction and wear performance and prevention of crack growth, with an ideal comprehensive properties.

scholarly journals Modelling of the densification of polar firn: characterization of the snow–firn transition

1998 ◽  
Vol 26 ◽  
pp. 39-44 ◽  
Author(s):  
L. Arnaud ◽  
V. Lipenkov ◽  
J. M Barnola ◽  
M. Gay ◽  
P. Duval
Keyword(s):  
Grain Boundary ◽  
Power Law ◽  
Grain Boundary Sliding ◽  
Boundary Sliding ◽  
Power Law Creep

The transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power-law creep. The observed decrease with temperature of the density at the snow-firn transition seems to result from the competition between grain-boundary sliding and power-law creep. These two densification processess occur concurrently in snow, although there are probably micro-regions in which sliding alone occurs. Validation of a geometrical densification model developed for ceramics has been obtained from densification data from several Antarctic and Greenland sites and from the characterization of the structure of polar firn.

scholarly journals Modelling of the densification of polar firn: characterization of the snow–firn transition

1998 ◽  
Vol 26 ◽  
pp. 39-44 ◽  
Author(s):  
L. Arnaud ◽  
V. Lipenkov ◽  
J. M Barnola ◽  
M. Gay ◽  
P. Duval
Keyword(s):  
Grain Boundary ◽  
Power Law ◽  
Grain Boundary Sliding ◽  
Boundary Sliding ◽  
Power Law Creep

The transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power-law creep. The observed decrease with temperature of the density at the snow-firn transition seems to result from the competition between grain-boundary sliding and power-law creep. These two densification processess occur concurrently in snow, although there are probably micro-regions in which sliding alone occurs. Validation of a geometrical densification model developed for ceramics has been obtained from densification data from several Antarctic and Greenland sites and from the characterization of the structure of polar firn.

scholarly journals Modelling the transition from grain-boundary sliding to power-law creep in dry snow densification

2021 ◽  
pp. 1-14
Author(s):  
Elizabeth M. Morris ◽  
Lynn N. Montgomery ◽  
Robert Mulvaney
Keyword(s):  
Grain Boundary ◽  
Transition Zone ◽  
Power Law ◽  
Transition Density ◽  
Grain Boundary Sliding ◽  
Smooth Transition ◽  
Physically Based ◽  
Boundary Sliding ◽  
Power Law Creep ◽  
Stage 1

Abstract This paper presents a physics-based macroscale model for the densification of dry snow which provides for a smooth transition between densification by grain-boundary sliding (stage 1) and densification by power-law creep (stage 2). The model uses established values of the stage 1 and 2 densification rates away from the transition zone and two transition parameters with a simple physical basis: the transition density and the half-width of the transition zone. It has been calibrated using density profiles from the SUMup database and physically based expressions for the transition parameters have been derived. The transition model produces better predictions of the depth of the nominal bubble close-off horizon than the Herron and Langway model, both in its classical form and in a recent version with re-optimised densification rates.

Molecular Dynamics Simulation of the Effect of Large Angle and Small Angle Grain Boundaries on the Near-Threshold Fatigue Crack Growth in Iron

2004 ◽  
Author(s):  
Shiro Kubo ◽  
Masaki Misaki
Keyword(s):  
Molecular Dynamics ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Crack Growth ◽  
Small Angle ◽  
Large Angle ◽  
Atomic Scale ◽  
Near Threshold

In the near-threshold region of the fatigue crack growth in metals, the amount of crack growth per cycle is in the order of the atomic scale. This may suggest that the near-threshold fatigue crack growth is controlled by atomic scale events. In previous papers the present authors applied the molecular dynamics to the simulation of near-threshold fatigue crack growth. In this study, the molecular dynamics method was applied to investigate the influence of inclined grain boundary on the near-threshold mode I fatigue crack growth behavior in BCC iron. Large angle grain boundaries served as an obstacle to the fatigue crack growth. Small angle grain boundaries had the effect of decreasing crack growth when the crack approached the grain boundary. When the crack reached the grain boundary it was trapped by the grain boundary.

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