Aluminum grain boundary decohesion by dense sodium segregation

2012 ◽  
Vol 85 (21) ◽  
Author(s):  
Shengjun Zhang ◽  
Oleg Y. Kontsevoi ◽  
Arthur J. Freeman ◽  
Gregory B. Olson
Keyword(s):  
Grain Boundary ◽  
Grain Boundary Decohesion

Grain boundary decohesion in body-centered cubic Mg-Li-Al alloys

2022 ◽  
pp. 163732
Author(s):  
Song Tang ◽  
Tongzheng Xin ◽  
Ting Luo ◽  
Fan Ji ◽  
Chuanqiang Li ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Al Alloys ◽  
Body Centered Cubic ◽  
Grain Boundary Decohesion

Ductile-brittle transition temperature shift controlled by grain boundary decohesion and thermally activated energy in Ni-Cr steels

2019 ◽  
Vol 37 (5) ◽  
pp. 455-458
Author(s):  
Jun Kameda ◽  
Martin L. Jokl
Keyword(s):  
Transition Temperature ◽  
Grain Boundary ◽  
Temper Embrittlement ◽  
Temperature Shift ◽  
High Hardness ◽  
Brittle Transition ◽  
Ductile Brittle Transition Temperature ◽  
Brittle Transition Temperature ◽  
Grain Boundary Decohesion ◽  
Medium Hardness

AbstractTemper embrittlement induced by segregation of metalloid solutes to grain boundary (GB) was evaluated by a shift of the ductile-brittle transition temperature (DBTT). DBTT was found to be linearly correlated with the amount of metalloid on the GB (Xgb) for both dynamic and static displacement rates (dδ/dt) in high and medium hardness steels. Recent first-principles calculations have determined the GB embrittling potency (Δep) of segregated Sb, Sn and P. In both high and medium hardness steels, the slope (α) of DBTT vs. Xgb was found to be linearly dependent on Δep regardless of the segregated solutes. In high hardness steels, the slope is independent of dδ/dt, while in medium hardness steels the α is dependent on dδ/dt. An Arrhenius plot of dδ/dt vs. the reciprocal DBTT was used to drive the thermal activation energy (Eact), which represents a barrier to plasticity. It was found that Eact correlates to a reduction in the GB fracture surface energy. The Eact depends strongly on GB decohesion in high hardness steels but only weakly depends on it in medium hardness steels.

On Hydrogen-Induced Void Nucleation and Grain Boundary Decohesion in Nickel-Base Alloys

2004 ◽  
Vol 126 (4) ◽  
pp. 368-377 ◽  
Author(s):  
Y. Liang ◽  
P. Sofronis
Keyword(s):  
Grain Boundary ◽  
Void Nucleation ◽  
Degradation Mechanism ◽  
Micromechanical Model ◽  
Hydrogen Effect ◽  
Cohesive Properties ◽  
Alloy 690 ◽  
Grain Boundary Decohesion ◽  
Nickel Base ◽  
Elastic Particle

Experimental evidence indicates that nickel-base alloys fail in the presence of hydrogen by ductile intergranular fracture. The degradation mechanism involves void nucleation at grain boundary carbides and grain boundary decohesion. In this study, a micromechanical model is suggested to understand the interaction of void nucleation and growth with the failure of the grain boundaries. The analysis is carried out at a unit cell comprising an elastic particle imbedded in a ductile matrix, a grain boundary along a plane of symmetry of the cell, and loaded in plane strain perpendicularly to the grain boundary. A phenomenological model for hydrogen-induced decohesion calibrated at the fast-separation limit of the decohesion theory of Rice [1], Hirth and Rice [2], and Rice and Wang [3] was used to describe the hydrogen effect on the cohesive properties of the particle/matrix interface and grain boundary. The finite element results indicate that hydrogen embrittlement of the alloy 690 is controlled by hydrogen assisted void nucleation at the carbides. The effect of hydrogen on grain boundary cohesion is almost negligible. The grain boundary decohesion, which proceeds almost instantaneously upon initiation, is caused by normal stress elevation due to the interaction of the void with the applied load. Lastly evaluative statements are made on the quantitative effect of hydrogen on the fracture toughness of the alloy 690.

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