Structure-dependent grain boundary deformation and fracture at high temperatures

In this study, the effects of the addition of Mg to the grain growth of austenite and the magnesium-based inclusions to mobility were investigated in SS400 steel at high temperatures. A high-temperature confocal scanning laser microscope (HT-CSLM) was employed to directly observe, in situ, the grain structure of austenite under 25 torr Ar at high temperatures. The grain size distribution of austenite showed the log-normal distribution. The results of the grain growth curves using 3D surface fitting showed that the n and Q values of the growth equation parameters ranged from 0.2 to 0.26 and from 405 kJ/mole to 752 kJ/mole, respectively, when adding 5.6–22 ppm of Mg. Increasing the temperature from 1150 to 1250 °C for 20 min and increasing the addition of Mg by 5.6, 11, and 22 ppm resulted in increases in the grain boundary velocity. The effects of solute drag and Zener pinning on grain boundary mobility were also calculated in this study.

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Grain Boundary Deformation Phenomena and Secondary Growth of Goss Grains in a Fe-3.5%Si Steel

ISIJ International ◽

10.2355/isijinternational.isijint-2017-119 ◽

2017 ◽

Vol 57 (10) ◽

pp. 1874-1882 ◽

Cited By ~ 2

Author(s):

Fatayalkadri Citrawati ◽

Md Zakaria Quadir ◽

Paul Richard Munroe

Keyword(s):

Grain Boundary ◽

Secondary Growth ◽

Boundary Deformation

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The “Solidification” of Grain Boundaries with Increasing Temperature

MRS Proceedings ◽

10.1557/proc-357-337 ◽

1994 ◽

Vol 357 ◽

Cited By ~ 1

Author(s):

Witold Lojkowski ◽

Bogdan Palosz

Keyword(s):

Solid State ◽

Melting Point ◽

Grain Boundary ◽

Grain Boundaries ◽

High Temperatures ◽

Low Temperatures ◽

Melting Behavior ◽

Wetting Transitions ◽

Increasing Temperature ◽

Segregation Of Impurities

AbstractThe aim of the paper is to explain the recently observed de-wetting grain boundary transition with increasing temperature. On the example of a bicrystal from the Fe-6at.%Si alloy, it was found recently that as temperature is increased, the following GB transitions take place: “solid” (or regular) GB-→“premelted” GB →“solid” GB. At the same time the wetting/de-wetting transitions have taken place. Another example of such GB behavior was discovered during sintering of alumina. The inverse melting behavior is explained as follows: low melting point impurities cause GB premelting at low temperatures, However de-segregation of impurities at high temperatures causes return of the GB structure to its regular “solid” state.

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The Effect of Interfacial Free Energies on the Stability of Microlaminates

MRS Proceedings ◽

10.1557/proc-652-y1.3 ◽

2000 ◽

Vol 652 ◽

Author(s):

A. C. Lewis ◽

A. B. Mann ◽

D. van Heerden ◽

D. Josell ◽

T. P. Weihs

Keyword(s):

Electron Microscopy ◽

Grain Boundary ◽

High Temperatures ◽

Free Energies ◽

Microstructural Stability ◽

Creep Tests ◽

Interfacial Energies ◽

Transmission Electron ◽

The Stability ◽

Interfacial Free Energies

ABSTRACTLaminated composites with polycrystalline layers typically break down at high temperatures through grain boundary grooving and the pinch-off of individual layers. Such materials, when exposed to high temperatures, develop grooves where grain boundaries meet the interfaces between layers. The depths of the grooves are controlled by the ratios of grain boundary and interfacial free energies, γgb/γint. Depending on the dimensions of the grains, these grooves can extend through the entire layer, causing pinch-off at the grain boundary. This pinch-off destroys the layering and eventually leads to a gross coarsening of the microstructure. Because microstructural stability is critical to performance for most applications, the ability to understand and predict the stability of microlaminates is a necessary tool. An existing model of this capillarity-driven breakdown requires the interfacial free energies, γgb and γint, as input parameters. Both biaxial and uniaxial zero creep tests have been used in conjunction with transmission electron microscopy to measure these interfacial energies in Ag/Ni and Nb/Nb5Si3 microlaminates.

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