Application of High-Density Electropulsing to Improve the Performance of Metallic Materials: Mechanisms, Microstructure and Properties

Abstract

The technology of high-density electropulsing has been applied to increase the performance of metallic materials since the 1990s and has shown significant advantages over traditional heat treatment in many aspects. However, the microstructure changes in electropulsing treatment (EPT) metals and alloys have not been fully explored, and the effects vary significantly on different material. When high-density electrical pulses are applied to metals and alloys, the input of electric energy and thermal energy generally leads to structural rearrangements, such as dynamic recrystallization, dislocation movements and grain refinement. The enhanced mechanical properties of the metals and alloys after high-density electropulsing treatment are reflected by the significant improvement of elongation. As a result, this technology holds great promise in improving the deformation limit and repairing cracks and defects in the plastic processing of metals. This review summarizes the effect of high-density electropulsing treatment on microstructural properties and, thus, the enhancement in mechanical strength, hardness and corrosion performance of metallic materials. It is noteworthy that the change of some properties can be related to the structure state before EPT (quenched, annealed, deformed or others). The mechanisms for the microstructural evolution, grain refinement and formation of oriented microstructures of different metals and alloys are presented. Future research trends of high-density electrical pulse technology for specific metals and alloys are highlighted.

Effect of Cold Deformation on Microstructures and Mechanical Properties of Austenitic Stainless Steel

“…Previous studies [25,26] have indicated that heavily cold worked metals could be subdivided by grain boundaries and dislocation boundaries. The cold work inducing the formation of the grain boundary was also found in CR AZ91 alloy [27] and 308L stainless steel [28]. In this 316LN ASS, in addition to dislocation grain boundaries, the boundaries of mechanical twins and strain-induced martensite formed during the CR process can also subdivide untransformed austenite, leading to the decrease of the untransformed austenite structure size.…”

Achieving the Control of Nonmetallic Inclusions Morphology and Orientation by Electric Current

“…In addition, due to the repulsion effect, the distance between inclusions (e.g., the inclusions M and N in Figure b) is greater than that of the untreated sample (Figure a). In fact, the electric current affects many other second phases whose conductivity are different from that of matrix . Electric current causes the fragment of lamellar cementite to be perpendicular to current .…”

Influence of Electropulsing Treatments on Mechanical Properties of UNS S32750 Duplex Stainless Steel

“…hence, a change in the residual stresses of the single phase was expected [30,[50][51][52][53]. An increase in compression stress amounts in ferrite after the first electropulsing treatment was determined and this did not change even after the electropulsing treatment at higher current density and higher number of pulses (Figure 16a).…”

“…Since tensile test introduces uniaxial stress configuration in the specimen, no variation in the average residual internal stresses was expected. On the other hand, electropulsing treatments have shown to induce changes in the grain orientation within the materials not to mention the change in morphology of secondary low conductivity phases (i.e., cementite particles in perlite) hence, a change in the residual stresses of the single phase was expected [30,[50][51][52][53]. An increase in compression stress amounts in ferrite after the first electropulsing treatment was determined and this did not change even after the electropulsing treatment at higher current density and higher number of pulses (Figure 16a).…”