Dissociated prismatic loop punching by bubble growth in FCC metals

Materials performance can be significantly degraded due to bubble generation. In this work, the bubble growth process is elaborated in Cu by atomistic modeling to bridge the gap of experimental observations. Upon continuous He implantation, bubble growth is accommodated first by nucleation of dislocation network from bubble surface, then formation of dissociated prismatic dislocation loop (DPDL), and final DPDL emission in $$\langle 110\rangle$$ ⟨ 110 ⟩ directions. As the DPDL is found capable of collecting He atoms, this process is likely to assist the formation of self-organized bubble superlattice, which has been reported from experiments. Moreover, the pressurized bubble in solid state manifests the shape of an imperfect octahedron, built by Cu $$\{111\}$$ { 111 } surfaces, consistent with experiments. These atomistic details integrating experimental work fill the gap of mechanistic understanding of athermal bubble growth in Cu. Importantly, by associating with nanoindentation testings, DPDL punching by bubble growth arguably applies to various FCC (face-centered cubic) metals such as Au, Ag, Ni, and Al.

Interactions between butterfly-like prismatic dislocation loop pairs and planar defects in Ni3Al

Understanding the interactions between planar defects and complex dislocation structures in a material is of great significance to simplify its design.

Molecular Dynamics Simulation on B3-GaN Thin Films under Nanoindentation

The B3-GaN thin film was investigated by performing large-scale molecular dynamics (MD) simulation of nanoindentation. Its plastic behavior and the corresponding mechanism were studied. Based on the analysis on indentation curve, dislocation density, and orientation dependence, it was found that the indentation depths of inceptive plasticity on (001), (110), and (111) planes were consistent with the Schmid law. The microstructure evolutions during the nanoindentation under different conditions were focused, and two formation mechanisms of prismatic loop were proposed. The “lasso”-like mechanism was similar to that in the previous research, where a shear loop can translate into a prismatic loop by cross-slip; and the extended “lasso”-like mechanism was not found to be reported. Our simulation showed that the two screw components of a shear loop will glide on another loop until they encounter each other and eventually produce a prismatic dislocation loop.

Formation of a Prismatic Dislocation Loop in the Interface of a Circular Cylindrical Inclusion Embedded in a Thin Slab

The introduction of a prismatic dislocation loop in the interface of an axisymmetric precipitate embedded in a thin slab of infinite lateral extension has been theoretically investigated. The critical misfit strain resulting from the lattice mismatch between the inclusion and the slab has been characterized for the loop formation versus the thickness of the slab and the radius of the inclusion. The case where the precipitate is embedded in a semi-infinite matrix is also discussed and a stability diagram of the structure is displayed with respect to the loop introduction versus the geometric and misfit parameters.