Deformation of copper single crystals to large strains at 4.2K

Thermally activated flow of dislocations in Al–Mg binary alloys

“…The figures also indicate a change in the dominant interaction mechanism of mobile dislocations with the obstacles, from coordinated passing of two partials to the mechanism involving passing by individual partial dislocations, as proposed by Nabarro [31]. The results are consistent with the behavior of the activation volume and activation distance discussed in Section 4.1 and studies of the microstructure evolution in copper single crystals, which show that the dislocation microstructure produced during plastic flow is progressively refined and contains an increasingly higher density of nanoscale defects comprising narrow dipoles, fine loops, nanosize stacking fault tetrahedra and clusters of point defects [25,29,26,27]. Similar processes are also expected to occur in Al-Mg alloys.…”

“…From the perspective of thermally activated flow these defects constitute the obstacle structure for mobile dislocations, characterized by a wide range of activation energies. Measurements of electrical resistivity of deformed Al and Cu show that a negligible change in electrical resistivity occurs upon unloading and annealing of deformed samples below 100 K [28,29]. The annihilation of deformation-induced resistivity proceeds at temperatures above 100 K, which suggests that in the present case of AlMg alloys SRS data can be analyzed in terms of the constant microstructure and without necessity to consider annihilation of defects during strain-rate changes.…”

Lattice correspondence during twinning in hexagonal close-packed crystals

“…Also, electrical resistivity studies of deformed copper show that a twinned substructure acquires an unusually high density of recoverable defects which anneal out at relatively low temperatures, indicating that heavy refinement of pre-existing defects occurs as a result of the interactions of twinning dislocations with these elements of the dislocation substructure [24]. However, many dislocations in fcc crystals transform as predicted by operation of the correspondence matrix [4,6,7].…”

Effects of composition and microstructure on behaviors of electrical resistivity during continuous heating above room temperature in Mg-based alloys

“…The resistances of the samples were obtained from the measured potential and known current. The detail description of the technique is given in [11]. The presented ER data in this work are normalized to the resistance of the samples at RT.…”