Dislocation transmission across grain boundary (GB) and activation of dislocation source in adjacent grains are considered common features of dislocation-GB interactions in regulating mechanical properties and behaviors of metallic materials and structures. However, it is currently unclear which of dislocation transmission and dislocation source activation plays the dominant role in regulating dislocation-GB interaction. To study the competition between dislocation transmission and dislocation source activation, a theoretical framework is established based on a dislocation pile-up model. It is found that both dislocation transmission and dislocation source activation exhibit strong dependence on the GB misorientation angle. The critical transmission stress derived based on an energy method also depends on the grain size in a scaling form similar to the Hall-Petch relation. The outgoing slip systems during dislocation transmission are successfully predicted and agree with experimental observations. Regarding the dislocation source activation, the critical activation stress is investigated by examining the local stress fields generated by single and multiple slip dislocation pile-ups. It is found that compared with single slip dislocation pile-up, the result of multiple slip dislocation pile-ups displays lower critical activation stresses and exhibits feature of sensitivity to loading direction, interpreting the reported results of dislocation source activation in polycrystals. Further comparison between dislocation transmission and dislocation source activation for ⟨100⟩ tilt GBs indicates that the dislocation transmission prevails at low angle GB, while dislocation source activation is prone to occur at high angle GB. Our theoretical studies quantify the dislocation-GB interaction induced by dislocation pile-ups, shed light on the competition between dislocation transmission and dislocation source activation, and might provide essential guidance for high-performance metallic material design.

Dislocation-grain boundary interaction in metallic materials: Competition between dislocation transmission and dislocation source activation

On the microstructure evolution during isothermal low cycle fatigue of β-annealed Ti-6242S titanium alloy: Internal damage mechanism, substructure development and early globularization

Comparative study of crack growth behaviors of fully-lamellar and bi-lamellar Ti-6Al-3Nb-2Zr-1Mo alloy

https://spiral.imperial.ac.uk/bitstream/10044/1/82368/7/1-s2.0-S0264127520306110-main%281%29.pdf

The role of microstructure on wear mechanisms and anisotropy of additively manufactured 316L stainless steel in dry sliding

Influence of second phases on fatigue crack growth behavior of nickel aluminum bronze

Effect of microstructure on the fatigue crack growth behaviour of a near-α Ti alloy

The pile-up of dislocations between two low-angle tilt boundaries (LATB) in an fcc crystal was simulated using three-dimensional discrete dislocation dynamics. The LATB was constructed using glissile edge dislocations stacked on each other. The dislocations in the pile-up were chosen such that their reactions with the dislocations in the LATB resulted in glissile junctions. Parallel pairs of dislocations were inserted to a maximum allowable value estimated from theoretical expressions. A resolved shear stress was applied and increased in steps so as to move the dislocations in the pile-up towards the boundaries. The shear stress required to break the lead dislocation from the wall was determined for varying spacings between the two boundaries. The shear stress and boundary spacing followed the Hall–Petch type relation. Dislocation pile-ups without a LATB were also simulated. The spacing of the dislocations in the pile-up with LATB was found to be closer (ie higher dislocation density) than that wi...

Interaction of dislocation pile-up with a low-angle tilt boundary: a discrete dislocation dynamics study

Interaction of dislocations with low angle tilt boundaries in fcc crystals

Effect of orientation and presence of hydride on the fatigue crack growth behavior of Zr–2.5wt% Nb

Discrete dislocation dynamics were used to determine the relative strengths of binary dislocation junctions in fcc crystals. Equilibrium junctions of different types Lomer, glissile, coplanar, and collinear were formed by allowing parallel dislocations of unequal length to react. The strengths were determined from the computed minimum strain rate versus the applied shear stress plots. The collinear configuration was found to be the strongest and coplanar the weakest. It was seen that the glissile junction could exist as two variants depending on which parent slip system the shear stress is applied. One variant of the glissile junction was found to be as strong as the collinear configuration.

/pdf/comparison-of-the-strength-of-binary-dislocation-junctions-1v230c8apc.pdf

Naisheel Verdhan

Papers

Effect of microstructure on the fatigue crack growth behaviour of a near-α Ti alloy

Interaction of dislocation pile-up with a low-angle tilt boundary: a discrete dislocation dynamics study

Interaction of dislocations with low angle tilt boundaries in fcc crystals

Effect of orientation and presence of hydride on the fatigue crack growth behavior of Zr–2.5wt% Nb

Comparison of the Strength of Binary Dislocation Junctions in fcc Crystals