Dislocation mobility in gum metal $\beta$-titanium alloy studied via $\mathit{in\; situ}$ transmission electron microscopy

In situ tensile tests in a transmission electron microscope were carried out on a “Gum Metal” $\beta$-titanium alloy. Conventional dislocation slip was observed to be the only mechanism occurring during the plastic deformation. The low mobility of screw dislocations was shown to be due to their core structure configuration. Nanometer-sized obstacles were also present but have a weaker effect on the dislocation mobility. The density of these obstacles and the variation in energy due to the core structure of screw dislocations were measured and compared to theoretical data in the literature.

Figure 1

Mobile dislocations produced during in situ tensile test; black arrows indicate expanding dislocation loops created via double cross slip; some slip traces are also indicated.

Figure 2

Typical motion of a screw dislocation (indicated by “A”) during in situ TEM tensile test; on each frame, the previous position of the moving part of the dislocation is highlighted with dashed lines, the black arrows indicate the direction of slip, and the tensile direction lies along the vertical direction of the figure.

Figure 3

Motion of nonscrew segments showing unresolved pinning points (arrows); “b” is the projection of the Burgers vector in the observation plane.