Seyed Masood Hafez Haghighat

In situ transmission electron microscopy of the interaction between a moving dislocation and obstacles of dislocation character in pure iron

In this study, we report our observation of the interaction between a moving dislocation and an obstacle of dislocation character in pure bcc-Fe using a TEM in situ straining experiment at room temperature. Our observations reveal that the interaction of a ½⟨1 1 1⟩ dislocation with a dislocation debris leads to a dislocation loop at the obstacle by Orowan mechanism. Hence, the strength of these obstacles is estimated to be in the range of Gb/L, which is higher than the strengthening induced by different nanometric defects of similar size.

Dislocation dynamics modeling of plastic deformation in single-crystal copper at high strain rates

Abstract Tensile deformation of single-crystal copper along [001] orientation is modeled. Single crystal is deformed at three sets of high strain rates, ranging from 103 to 105 s−1, using the three-dimensional dislocation dynamics technique to simulate dislocation microstructure evolution and the resultant macroscopic response. Two initial dislocation configurations consisting of straight dislocations and Frank–Read sources are randomly distributed over the simulation volume with an edge length of 1 μm. For both initial setups, the mechanical response of the single crystal to the external loading demonstrates a considerable effect of strain rate. In addition, strain rate influences dislocation density evolution and consequently development of the dislocation microstructure. At all applied strain rates for both initial dislocation setups, dislocations evolve into a heterogeneous microstructure and this heterogeneity increases with plastic strain and strain rate.