Creep rupture strength and grain-boundary sliding in austenitic 21 Cr-4Ni-9Mn steels with serrated grain boundaries

1988 ◽  
Vol 23 (2) ◽  
pp. 621-628 ◽  
Author(s):  
Manabu Tanaka ◽  
Ohmi Miyagawa ◽  
Tsuneaki Sakaki ◽  
Hiroshi Iizuka ◽  
Fumio Ashihara ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Rupture Strength ◽  
Grain Boundary Sliding ◽  
Creep Rupture ◽  
Creep Rupture Strength ◽  
Boundary Sliding

Research on Micro-Mechanism of Nanocomposite Ceramic in Two-Dimensional Ultrasound Grinding

2007 ◽  
Vol 359-360 ◽  
pp. 344-348 ◽  
Author(s):  
Bo Zhao ◽  
Yan Wu ◽  
Guo Fu Gao ◽  
Feng Jiao
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Deformation Mechanism ◽  
Ground Surface ◽  
Grain Boundary Sliding ◽  
Second Phase ◽  
Two Dimensional ◽  
Composite Ceramics ◽  
Nano Composite ◽  
Boundary Sliding

Surface microstructure of nano-composite ceramics prepared by mixed coherence system and machined by two-dimensional ultrasonic precision grinding was researched using TEM, SEM, XRD detector and other equipments. Structure, formation mechanism and characteristic of metamorphic layer of ground surface of nano-composite ceramics were researched. The experiment shows micro deformation mechanism of ceramic material in two-dimensional ultrasound grinding is twin grain boundary and grain-boundary sliding for Al2O3, and it is crystal dislocation of enhanced phase, matrix grain boundary sliding, coordination deformation of intergranular second phase as well as its deformation mechanism for nano-composite ceramics. The fracture surfaces of nano-composite materials with different microscopic structure were observed using TEM and SEM. Research shows that ZrO2 plays an important influence on the generation and expansion of crack, and enhances the strength of grain boundaries. When grain boundaries is rich in the ZrO2 particles, the crack produced in grinding process will be prevented, and the surface with plastic deformation will be smooth. The results shows nanoparticles dispersed in grain boundary prevents crack propagation and makes materials fracture transgranularly which makes the processed surface fine.

scholarly journals Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

Solid Earth ◽  
2017 ◽  
Vol 8 (6) ◽  
pp. 1193-1209 ◽  
Author(s):  
James Gilgannon ◽  
Florian Fusseis ◽  
Luca Menegon ◽  
Klaus Regenauer-Lieb ◽  
Jim Buckman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Finite Strain ◽  
Grain Boundary Sliding ◽  
Large Strains ◽  
Cavity Formation ◽  
Phase Mixing ◽  
Transient Phenomena ◽  
Boundary Sliding

Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.

scholarly journals Grain Boundary Sliding and Atomic Structures in Alumina Bicrystals with [0001] Symmetric Tilt Grain Boundaries

2002 ◽  
Vol 43 (7) ◽  
pp. 1561-1565 ◽  
Author(s):  
Tsuyoshi Watanabe ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma ◽  
Hiroyuki Muto ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Atomic Structures ◽  
Symmetric Tilt ◽  
Boundary Sliding

Simulation of Microcrack Propagation in Creeping Polycrystals Due to Diffusive Grain Boundary Cavitation

1994 ◽  
Vol 47 (1S) ◽  
pp. S122-S131 ◽  
Author(s):  
M. W. D. van der Burg ◽  
E. van der Giessen
Keyword(s):  
Grain Boundary ◽  
Life Time ◽  
Grain Boundary Sliding ◽  
Creep Rupture ◽  
Network Modelling ◽  
Microcrack Propagation ◽  
Polycrystalline Aggregates ◽  
Boundary Sliding ◽  
Creep Deformations ◽  
Excessive Number

Creep rupture in random polycrystalline aggregates is investigated numerically in terms of multi-grain cell studies using a Delaunay network modelling technique. The model involves a representation of the crystalline aggregate by means of special purpose elements attributed to each grain facet. These Delaunay elements account for elastic and creep deformations of the grains, free grain boundary sliding, as well as for the nucleation and diffusive growth of grain boundary cavities until coalescence leads to a facet microcrack. Damage accumulation is simulated numerically, until an excessive number of microcracks cause des-integration of the polycrystal. Primary attention is on the influence of randomness in the microstructure on creep rupture, either in terms of random variations of the size and shape of hexagonal grains, or in terms of random variations in the nucleation properties of grain boundaries. It is found that randomness always tends to decrease the life time. In particular, it is found that the life time depends sensitively on random variations of the geometry of the microstructure.

Effects of Heterogeneous and Homogenous Laves Phase Precipitation on Creep Rupture Strength of Fe-9Cr-3Co (wt.%) Alloys at 650 °C

2014 ◽  
Vol 1081 ◽  
pp. 187-191
Author(s):  
S. Zhu ◽  
M. Yang ◽  
Xin Li Song ◽  
Z. Zhang ◽  
S. Tang ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Stress Exponent ◽  
Lave Phase ◽  
Rupture Strength ◽  
Creep Rupture ◽  
Laves Phase ◽  
Rupture Time ◽  
Stress Range ◽  
Creep Rupture Strength ◽  
Phase Precipitation

The relationship between creep rupture strength and Laves phase precipitation and growth kinetics was investigated at 650 °C for two Fe-9Cr-3Co (wt.%) alloys differing mainly in the amounts of W and Mo added. In the alloy with 3.14 wt.% W added, Laves phase precipitated heterogeneously on grain boundaries and hence had little dispersion strengthening effect. Its stress exponent for rup-ture time became lower in the lower creep stress range tested. In the alloy with 1.31 wt.% W and 3.22 Mo added, Laves phase precipitated both heterogeneously on grain boundaries and homogenously within grains and there was no reduction in stress exponent for rupture time in the whole stress range tested. The Lave phase precipitation kinetics increased with increasing the total amount of W and Mo in the alloys. The differences in stress-rupture time relationship observed between the two alloys were discussed in relation to their differences in the Lave phase precipitation behaviour.

scholarly journals Diffusion-Accommodated Grain Boundary Sliding in a Polycrystal

1990 ◽  
Vol 196 ◽  
Author(s):  
P. M. Hazzledine ◽  
J. H. Schneibel
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Diffusional Creep ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Material Deposition ◽  
Two Dimensional Model ◽  
Boundary Sliding ◽  
Coble Creep

ABSTRACTA two-dimensional model for diffusional creep (Coble creep) and diffusionaccommodated grain boundary sliding in polycrystals has been developed. The results obtained for small symmetrical clusters of grains reproduce Spingam and Nix's work [Acta Metall. 2M, 1389 (1978)]. For clusters of irregularly shaped grains the material deposition and removal rates, the fluxes along the grain boundaries, the grain boundary tractions as well as the grain boundary sliding rates are irregular and can all be calculated.

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