Abstract
Even though the fundamental rules governing dislocation activities have been well established in the past century, we report a phenomenon, dislocation transformation, governed by the generalized-stacking-fault energy surface mismatch (GSF mismatch for short) between two co-existing phases. By carrying out ab-initio-informed microscopic phase-field simulations, we demonstrate that the GSF mismatch between a high symmetry matrix phase and a low symmetry precipitate phase can transform an array of identical full dislocations in the matrix into an array of two different types of full dislocations when they shear through the precipitates. The precipitates serve as a passive Shockley partial source, creating new Shockley partial dislocations that are neither the ones from the dissociation of the full dislocation. This phenomenon enriches our fundamental understanding of partial dislocation nucleation and dislocation-precipitate interactions, offering additional opportunities to tailor work-hardening and twinning processes in alloys strengthened by low-symmetry precipitate phases.
Highlights
The theory of dislocations is an important cornerstone in crystal physics
There are some longstanding consensuses on dislocation nucleation, multiplication, and interaction with other extended defects in a crystal
When dislocations meet homo-phase interfaces such as grain/twin boundaries in polycrystalline materials, they could be absorbed into the interfaces or transmitted to the other side of the interfaces, the latter is referred to as slip transmission or transmutation[4], where the transmitted dislocations can have different slip planes and Burgers vectors
Summary
The theory of dislocations is an important cornerstone in crystal physics. It was initially proposed to solve the puzzle of why a crystal yields at one-hundredth of its ideal strength[1], and among the later advancements the mechanisms of dislocation generation and multiplication are probably the most fundamental concepts. During plastic deformation of crystalline materials, dislocations carry the plastic flow by multiplying themselves through mechanisms like the Frank-Read source[2] and double cross slip[3], leading to a massive dislocation population explosion Their mutual interactions as well as interactions with other extended defects present in the crystals generate a rich variety of deformation microstructures that underpin all the important mechanical properties including yield strength, work-hardening ability, ultimate strength, ductility, fracture toughness, creep resistance, etc. We demonstrate a concept referred to as generalized stacking fault energy surface mismatch (will be referred to as GSF mismatch hereafter) between matrix and precipitate phases Because of such a GSF mismatch, an array of partial dislocations can nucleate in the low-symmetry precipitate phase when an array of full dislocations with the same Burgers vector (like those generated by a Frank-Read source) shear through the precipitates, leading to a change in the dislocation content when they exit the precipitates. The results uncovered in this work provide an essential piece in understanding dislocationprecipitation interaction and adds another perspective on dislocation generation and multiplications
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