3D-Atom Probe Investigation of Vacancy Induced Interdiffusion during High Pressure Torsion Deformation

Abstract

Concentration gradients resulting from long range diffusion during Severe Plastic Deformation (SPD) have been investigated with the 3D Atom Probe technique (3D-AP). First, in a pearlitic steel where alloying elements (Mn, Si and Cr) are partitioned between the ferrite and carbides in the non-deformed state. After processing by High Pressure Torsion (HPT), they are homogeneously distributed in the nanostructure, indicating that long range diffusion occurred along with the dissolution of carbides. 3D-AP data of a Cu-Fe composite processed by HPT show as well a significant interdiffusion of Cu and Fe, probably promoted by additional vacancies. On the basis of these experimental data, and using the theory described for irradiated materials, vacancy fluxes and vacancy production rates were estimated assuming that new vacancies are continuously produced and eliminated on grain boundaries.

Softening by severe plastic deformation and hardening by annealing of aluminum–zinc alloy: Significance of elemental and spinodal decompositions

“…(2)) because of active contribution of short-circuit diffusion as well as a significant increase in vacancy population. Related evidences for the reduction of Q were reported earlier with SPD-processed materials, especially at low temperatures [73][74][75][76].…”

“…However, a question arises if it is feasible for the decomposition to proceed within several minutes of HPT operation at ambient temperature. It is most conceivable that atomic diffusion must be accelerated by the HPT processing because of the generation of high-density lattice defects as reported in other papers [73][74][75][76]. In addition to the atomic diffusion, dynamic recovery and dynamic recrystallization also can affect the elemental decomposition.…”

Homogeneous Cu–Fe supersaturated solid solutions prepared by severe plastic deformation

“…In such conditions, as demonstrated by Sato and co-authors [42], the migration energy of vacancies may be reduced by 30%. As suggested in our earlier studies, such conditions sufficiently enhance the diffusion rate of Fe in fcc Cu to account for bulk diffusion at room temperature [17,45]. However, the present investigations clearly show that at cryogenic temperature (77K) large amounts of homogeneous ssss can be obtained while the mobility of vacancies is not significant.…”

Nanostructure and properties of a Cu–Cr composite processed by severe plastic deformation

“…2(d)). This indicates that even if some dislocations could act as diffusion pipe, the atomic mobility might be mostly enhanced by SPD induced vacancies [21].…”

“…2(d)). This indicates that even if some dislocations could act as diffusion pipe, the atomic mobility might be mostly enhanced by SPD induced vacancies [21]. Previous studies on ball milled powders or sputtered thin films have demonstrated that phase separation in Cu-Cr SSSS starts in a temperature range of 400 to 500°C.…”