scholarly journals The Influence of Grain Boundaries on Deformation and Fracture of Metallic Materials at High Temperatures

1974 ◽  
Vol 23 (246) ◽  
pp. 167-173
Author(s):  
Sadao OHTA
Keyword(s):  
Grain Boundaries ◽  
High Temperatures ◽  
Metallic Materials ◽  
Deformation And Fracture

Observation of secondary slip systems in tungsten bicrystals

1984 ◽  
Vol 42 ◽  
pp. 478-479
Author(s):  
J. R. Fekete ◽  
R. Gibala
Keyword(s):  
Stress Field ◽  
Grain Boundaries ◽  
Deformation Behavior ◽  
Stress Axis ◽  
Polycrystalline Materials ◽  
Slip Systems ◽  
Metallic Materials ◽  
Twist Boundary ◽  
Secondary Slip ◽  
Plane Normal

The deformation behavior of metallic materials is modified by the presence of grain boundaries. When polycrystalline materials are deformed, additional stresses over and above those externally imposed on the material are induced. These stresses result from the constraint of the grain boundaries on the deformation of incompatible grains. This incompatibility can be elastic or plastic in nature. One of the mechanisms by which these stresses can be relieved is the activation of secondary slip systems. Secondary slip systems have been shown to relieve elastic and plastic compatibility stresses. The deformation of tungsten bicrystals is interesting, due to the elastic isotropy of the material, which implies that the entire compatibility stress field will exist due to plastic incompatibility. The work described here shows TEM observations of the activation of secondary slip in tungsten bicrystals with a [110] twist boundary oriented with the plane normal parallel to the stress axis.

DYNAMIC STUDIES OF DEFORMATION AND FRACTURE AT GRAIN BOUNDARIES

1988 ◽  
Vol 49 (C5) ◽  
pp. C5-677-C5-680
Author(s):  
I. M. ROBERTSON ◽  
G. M. BOND ◽  
T. C. LEE ◽  
D. S. SHIH ◽  
H. K. BIRNBAUM
Keyword(s):  
Grain Boundaries ◽  
Dynamic Studies ◽  
Deformation And Fracture

The “Solidification” of Grain Boundaries with Increasing Temperature

1994 ◽  
Vol 357 ◽  
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.

Experimental Evidence For Sulfur Induced Loss Of Ductility In Copper Shaped-Charge Jets

1995 ◽  
Vol 409 ◽  
Author(s):  
D. K. Chan ◽  
D. H. Lassila ◽  
W. E. King ◽  
E. L. Baker
Keyword(s):  
Grain Boundaries ◽  
Sulfur Content ◽  
Fracture Behavior ◽  
High Strain ◽  
Shaped Charge ◽  
X Ray ◽  
Jet Breakup ◽  
Deformation And Fracture ◽  
Breakup Time ◽  
Content Of Oxygen

AbstractWe have observed that a change in the bulk sulfur content of oxygen-free electronic copper markedly affects its high temperature (400–1000°C), high strain-rate (> 103 s−1) deformation and fracture behavior. These conditions are typical of those found in "jets" formed from the explosive deformation of copper shaped-charge liners. Specifically, an increase in the bulk sulfur concentration from 4 ppm to 8 ppm shortens the breakup time, tb, of the copper jets by nearly 20% as measured using flash x-ray radiographs recorded during breakup of the jets. At bulk concentrations of 4 ppm, the jet was observed to be uniform and axisymmetric with a breakup time of 186 µs. Jet particles exhibited length-to-diameter ratios of roughly 8:1. The addition of sulfur transformed the jet breakup behavior to non-uniform, non-axisymmetric rupture and reduced the breakup time to 147 µs. The length-to-diameter ratios decreased to roughly 5:1 in the sulfurdoped samples. Previously measured sulfur solubilities and diffusivities in copper at the temperatures where this material was processed indicates nearly all of the sulfur was localized to grain boundaries. Therefore, we infer that the increase in sulfur content at grain boundaries is directly responsible for the change in breakup performance of the shaped-charge jets.

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