Mechanisms of pore defects evolution in Mo14Re alloy welded joints under dislocation back stress

Abstract

Mo14Re alloy is widely utilized in aerospace and nuclear energy applications due to its exceptional high-temperature mechanical properties and radiation resistance. Despite its significant high-temperature stability, the presence of pore defects seriously damages the mechanical properties of the alloy. This study combines crystal plasticity finite element simulation to reveal the influence mechanism of dislocation back stress on pore defects in Mo14Re alloy welded joints. In the fusion zone (FZ), the formation of pore defects is primarily influenced by differences in Schmid factors, stress concentration, and dislocation motion. Grains with high Schmid factors are more prone to dislocation movement and significant deformation, while grains with low Schmid factors exhibit weaker deformability, leading to stress concentration at grain boundaries and suppressing dislocation motion around pores. This exacerbates local deformation inhomogeneity and promotes pore formation. In the weld zone (WZ), the formation of pore defects is closely related to stress concentration and dislocation motion. Stress concentration typically occurs at grain boundaries, triggering the generation and propagation of dislocations. This often results in uneven plastic deformation, leading to insufficient deformation in certain areas and the formation of pore defects. In the FZ, lower energy input restricts dislocation motion at subgrain boundaries, leading to stress concentration and back stress accumulation, which promotes pore defect formation. In contrast, the higher energy in the WZ increases dislocation strain energy, enabling dislocations to overcome subgrain boundaries more easily.