Electropulsing Treatment Research Articles

Effects of electropulsing treatment on the microstructural evolution of hot-rolled TiBw/TA15 composite billet with a network architecture

The use of resistance heating patterns is one of the underlying opportunities for the hot processing of hard-working materials. Here, the effect of electropulsing treatment (EPT) on the microstructure of a hot-rolled TiBw/TA15 composite billet with a network architecture was investigated. Experimental results showed that the stable temperature platform presented a competition between Joule heat and heat dissipation, including heat conduction, convection, and radiation, and the temperature distribution was non-uniform. The ultimate temperatures of the EPT samples increased gradually as the electropulsing increased. Then, the traditional heat treatment sample was compared with the EPT samples via electron backscatter diffraction, scanning electron microscopy, and X-ray diffraction. Results of analyses indicate that the athermal effect independent from electropulsing can promote the growth of grains, but it also decreases the dislocation density and increases the recrystallization fraction. Therefore, athermal effects can exist authentically in contrast to the thermal effects, and specific thermal effects can hardly achieve the results obtained in this study.

Prolonged fatigue life in aluminum clad steel by electropulsing treatment: Retardation of interface-microcrack formation

The prolonged fatigue life of aluminum clad steel (Al clad steel, ACS) using electropulsing treatment is systematically investigated by characterizing the microstructural change at different fatigue cycles. The microstructural changes associated with fatigue damage evolution show that cracks are prone to initiate at Al grains of the interface and propagate toward the Al side in the fatigue test due to a preferred accumulation of geometrically necessary dislocations (GNDs) in the soft Al grains near the interface. The electropulsing treatment with a subsecond duration is proved to be efficient in healing the fatigue damage and significantly prolonging the fatigue life of the ACS. The increased fatigue life by electropulsing treatment is attributed to the diminished density of piled GNDs and the retardation of microcrack formation at the interface. The present study elucidates the failure mechanism of ACS and proves that electropulsing treatment is an efficient method to prolong the fatigue life of laminated metal composites by healing the accumulated damage during the fatigue test.

A novel strategy for preparation of α′ + β Dual-phase microstructure through heating massive-like transformation induced by Electropulsing in Ti-6Al-4V Alloy

A novel dual-phase microstructure (α′ + β) has been prepared in Ti-6Al-4V alloy, which breaks the trade-off effect between strength and plasticity during the traditional solution treatment. This result is attributed to the rapid heating-induced massive-like transformation (α + β → βm) via electropulsing treatment and following martensitic transformation (βm → α′ + β) by water quenching. It was found that there was almost no alloy elements diffusion during the whole transition. Therefore, different from the traditional solution treatment product of V-supersaturated α′, the Al-enriched α′ and remained β were obtained.

Improved mechanical properties of Mg-1Gd alloy by cold rolling and electropulse treatment

• Mg-1Gd alloy is processed by “cold rolling + electropulse treatment (EPT)”. • The time to finish recrystallization is greatly shortened to 40 s. • Mg-1Gd alloy with a good balance between strength and ductility is obtained by EPT. In this work, a simple processing scheme of “cold rolling + electropulse treatment (EPT)” was proposed and conducted on Mg-1Gd (G1) alloy. Compared with the conventional heat treatment (HT), significantly shortened treatment duration (40 s) and a good balance between ultimate tensile strength (∼198.7 MPa) and elongation-to-failure (∼20.2 %) of the alloy were obtained, when the peak current density was 152.5 A/ m m 2 . According to the results of fracture morphology and microstructure characterization, the improved mechanical property of G1 alloy is supposed to be resulted from the uniform grain structure, weakened texture, and selective heating effect of EPT, which can heal the micro-crack generated during cold rolling.

Plastic deformation of AZ31B magnesium alloy in the preform and electropulsing treatment process

Magnesium alloys exhibit poor formability at room temperature owing to their hexagonal close-packed crystal structure. In this study, a multi-step preform and electropulsing treatment method was applied to the plastic deformation of AZ31B magnesium alloy to improve its cumulative ductility. The mechanical properties, microstructure, and dislocation evolution were investigated using various parameters. The cumulative elongation of all specimens increased significantly, with the maximum approximately twofold higher for the initial specimens. Although the yield strength decreased after the first step, it increased with the following steps. After electropulsing treatment, the specimens were recrystallized and the dislocations were annihilated. The deformed microstructure caused by preform recovered and the recovery degree was associated with the preform and electropulsing treatment parameters. Therefore, the preform and electropulsing treatment method is effective to enhance the ductility of AZ31B magnesium alloy at room temperature, and a set of appropriate pulse current parameters can achieve satisfactory strength and elongation results. Moreover, the effect of the pulse current on the dislocation mobility and climb mainly accounts for the beneficial restoration during the preform and electropulsing treatment process.

Rapid Microstructure Homogenization of a Laser Melting Deposition Additive Manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si Alloy by Electropulsing.

The typical microstructure of the laser melting deposition (LMD) additive-manufactured Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy (TC11) contains the heat-affected bands (HABs), the narrow bands (NBs) and the melting pools (MPs) that formed due to the reheating and superheating effects during the layer-by-layer manufacturing process. Characterization results indicated that the coarse primary α lath (αp) and transformed β (βt) structures were located in the HABs, while the fine basketweave structure was formed inside the MPs. The rapid modifications of microstructure and tensile properties of the LMD-TC11 via electropulsing treatment (EPT) were investigated. The initial heterogeneous microstructure transformed into a complete basketweave structure and the HABs vanished after EPT. Thus, a more homogeneous microstructure was achieved in the EPT sample. The ultrafast microstructural changes were mainly attributed to the solid state phase transformation during electropulsing. The tensile properties of the sample were basically stable, except that the yield strength decreased as EPT voltage increased. This study suggests that EPT could be a promising method to modify the microstructure and mechanical properties of the additive-manufactured alloys in a very short time.

Effect of electropulsing and annealing treatment on microstructure and mechanical properties of 316L stainless steel

Considering the consumption of time and energy for the traditional heat treatment process, a new heat treatment method with high speed and low energy consumption has always been the direction of researchers. The microstructure and mechanical properties of engineering 316L stainless steel were measured under electropulsing treatment within 400 ns and annealing treatment for 2 h. Compared with the original cold-rolled state, it was found that the yield strength after 3.8 × 103 A/mm2 electropulsing treatment was reduced by 26.2% and that after 800 °C heat treatment was reduced by 27.7%. The nucleation after electropulsing treatment is mainly concentrated at one end of the lamellar grain and finally grows into the square or rhombic grain with an average grain size of 1.5 µm. After annealing, the nucleation is mainly concentrated at the grain boundaries of the lamellae and finally grows into equiaxed grains with an average grain size of 1.8 µm. Under the action of electronic wind, the recrystallization nucleation after electropulsing is mainly dominated by the mechanism of subgrain nucleation and growth. However, under the action of a uniform thermal field, the recrystallization nucleation after annealing is mainly based on the grain boundary bow-out mechanism.

Influence of electropulsing treatment on crystallization and structure of calcium silicate-based melt

Electropulsing treatment (EPT) is a promising technology for controlling the phase transition during the solidification of melts owing to its electric and thermal effects. In this study, the influence of EPT on the crystallization and melt structure of a calcium silicate-based mold flux was investigated. The results showed that the morphology of crystals that precipitated in the mold flux changed from elongated columnar to block shape, and the equivalent grain diameter of the crystals increased with increasing voltage from 0 to 20 V. The mass fraction of Ca4Si2O7F2 precipitated in the mold flux decreased with increasing impulse voltage, whereas that of Ca2Mg0.75Al0.5Si1.75O7 increased. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses suggest that the network structure of both silicate and aluminate was simplified by electropulsing because the simpler structural units of Q0, Q1, [AlO6]9+, etc., increased with increasing impulse voltage, whereas the complex structural units of Q2, Q3, and [AlO4]5+ decreased. The extra electric field force is the repulsion force between two oppositely charged ions, which was the root of the network structure simplification and crystallization promotion. The results obtained in this study provide an innovative method for locally controlling the crystallization behavior of mold flux in a mold.

Effects of induced electro-pulsing and aging process on properties and microstructure of 7075 aluminum alloy

The effect of induced electro-pulsing of 7075 aluminum alloy in solid solution and pre-deformation was studied. The tensile test results show that material plasticity is recovered and strength is increased by induced electro-pulsing treatment (IEPT). As the discharge time increases, the increase in elongation becomes more obvious. Yield strength, tensile strength, and elongation of once-treated samples increased by 3.7%, 1.3%, and 9.7%, respectively, compared with the untreated sample; Those of twice-treated samples increased by 6.4%, 6.4%, and 27.8%. Microstructure characterization showed that the induced current reduces the dislocation density of the material and promotes advanced precipitation of Guinier-Preston (GP) zones. In addition, the strength of treated samples and untreated samples was almost the same after peak aging treatment, while the elongation increased by 12.15%. High resolution transmission electron microscopy (HRTEM) images show that the size of the η’ phase in the treated alloy is smaller and the alloy exhibits better ductility.

Effect of electropulsing treatment on microstructure and mechanical properties of Cu–20Ni–20Mn alloy

The microstructure evolution and mechanical properties changes of the deformation-aged Cu–20Ni–20Mn alloy during electropulsing treatment (EPT) were investigated. The results indicate that, compared with the deformation-aged Cu–20Ni–20Mn alloy with a tensile strength of 942 MPa and an elongation of 1.4% in the previous study, the tensile strength and elongation of the deformation-aged Cu–20Ni–20Mn alloy after EPT with je (the root-mean-square value of pulse current density) of 10.7 A/mm2 for 150 s increased to 950 MPa and 11.3%, respectively. Fine recrystallized grains, local high density dislocation tangles and local uniformly distributed θ-MnNi phases were found in the microstructure of alloy after EPT, which played a key role in improving the strength and ductility of alloy simultaneously. The θ-MnNi phases distributed in the vicinity of dislocation tangles were more preferentially dissolved into the α-Cu matrix under the thermal effect and athermal effect of EPT than the θ-MnNi phases at grain boundaries. The kinetic energy from electron momentum (athermal effect) provided by EPT, which triggered the atomic diffusion accompanied by dislocation movement, leading to the acceleration of recovery, recrystallization processes of alloy and the dissolution of θ-MnNi phases. The results provide guidance for the strength-ductility simultaneous enhancement of various metallic materials.

Effect of Pulse Current Density on Microstructure of Ti-6Al-4V Alloy by Laser Powder Bed Fusion

This work thoroughly investigated the microstructure of laser powder bed fusion (LPBF) Ti64 alloy induced by electropulsing (ECP) with different current densities. The results show that as the electric current density increases, the small-sized (<10 μm) α′ martensites increase and the large-sized (>10 μm) α′ martensites decrease, resulting in a typical grading microstructure treated by the ECP treatment. The thermodynamic barrier was found to decrease as the electric current passed, recrystallization occurred, and the percentage of small-sized α′ martensites increased. At the same time, the unique electrothermal coupling effect of ECP treatment acted on the needle-like α′ martensites, causing an energy concentration on the tip to break the adjacent α′ martensite and the percentage of large-sized α′ martensites to decrease. When the current density of ECP treatment was 48.37 A/mm2, the grading phenomenon of acicular α′ martensites was the most obvious and its size distribution changed significantly, which simultaneously improved the strength and elongation of LPBF-Ti64 alloy. Thus, the typical grading phenomenon of the α′ martensites plays a decisive role in improving the mechanical properties of the LPBF-Ti64 samples induced by the ECP treatment. The present results provide new information on the ECP processing additive manufacturing metallic materials.

Extraordinary ductility enhancement of Mg-Nd-Zn-Zr alloy achieved by electropulsing treatment

Mg-Nd-Zn-Zr (JDBM) alloy was studied as a candidate for biodegradable implant material because of its moderate mechanical properties, good biocompatibility, and favorable uniform degradation behavior. To verify whether JDBM alloy exhibits electroplasticity effect and then study the mechanism of electropulsing treatment on JDBM alloy, in this study, homogenized and pre-tensile deformed samples were treated by electropulsing. After the electropulsing treatment, the average grain size was refined due to recrystallization, micron-scale Mg12Nd secondary phases precipitated slightly, while the morphology of nanoscale Zr particles changed from rodlike to ellipsoidal shape. The elongation to failure (EL) increased obviously for the homogenized and pre-tensile deformed JDBM alloy samples after electropulsing treatment, accompanying with no obvious sacrifice of the yield strength (YS) for the former and an evident decrease of YS for the latter, mainly due to the reduction of the dislocation density. The YS decrement and EL increment (77.57%) for the latter are more apparent attributed to the higher density of dislocations introduced by pre-tensile deformation. Therefore, the electropulsing treatment can obviously improve the mechanical properties of JDBM alloy, especially for the plasticity. The present work opens a new window for the fabrication of JDBM alloy profiles with high mechanical properties, especially for the plasticity, such as the cold drawing wires and tubes for biomedical applications. It also could provide theoretical references for other magnesium alloy processing.

Texture tailoring of a cold-rolled Mg-Zn-Gd alloy by electropulse treatment: The effect of electropulse and Gd element

Electropulse treatment (EPT) was utilized to tailor the texture of a cold-rolled Mg-rare earth (RE) alloy (Mg-1Zn-1Gd, ZG11). The respective effect and combined effect of electropulse and Gd element on the texture modification were evaluated by using conventional heat treatment (HT) and AZ31 alloy for comparison. It was found that in addition to significantly accelerating static recrystallization (SRX), electropulse was effective in suppressing the growth advantage of basal oriented grains and facilitating uniform growth, according to the evolution of 30° 〈0001〉 boundaries. As widely reported, addition of Gd element was observed to promote shear band-related nucleation and preferential growth of off-basal oriented grains via grain boundary segregation; unfortunately, the growth advantage of basal oriented grains seemed not to be well-suppressed. When electropulse was exerted on cold-rolled ZG11, the SRXed grains showed obvious off-basal orientations at the early stage benefited from various nucleation sites, e.g., shear bands, extension twin boundaries, and the off-basal orientations were retained to a great extent during grain growth due to the synergetic effect of electropulse and grain boundary segregation on grain boundary migration. As a consequence, the ZG11 alloy evolved into a quite distinctive SRX texture after EPT.

Impact of the pulse induced current on the microstructure and mechanical properties of the 7075-T6 aluminum alloy

The effect of the pulse induced current on the mechanical properties and microstructure of the 7075-T6 aluminum alloy was thoroughly studied by transmission electron microscopy, X-ray diffraction, and electron backscattered diffraction measurements. The experimental results demonstrated that the strength of the alloy decreases slightly, whereas the elongation increases significantly. On top of that, after the application of the induced electro-pulsing treatment, the dislocation density of the alloy decreases, while the grain size and the second phase particles grow slightly. In addition, the induced current also causes the Cube, Copper and S textures to decrease. On the other hand, the Goss texture is enhanced. The current density and the local temperature distribution of the sample were simulated by employing the ANSYS software. From the acquired outcomes, we can draw the conclusion that the recorded changes in the mechanical properties and microstructure of our sample can be attributed to the combination of the joule phenomenon and the pure electric effects of the current. The Joule heat and current increase the vacancy concentration and diffusion coefficient of solute atoms and promote dislocation recovery, precipitation phase growth, and grain rotation. • Induced electro-pulsing treatment (IEPT) is used to change the properties of 7075-T6 aluminum alloy. • After IEPT, the plasticity of the alloy is significantly improved while the strength is slightly decreased. • It is found that induced current can reduce dislocation density, promote grain rotation and change texture type.

Effect of electropulsing on anisotropy in strength of laser metal deposited Ti−6Al−4V alloy

The effect of electropulsing treatment on microstructure and mechanical strength of laser metal deposited Ti−6Al−4V alloy was investigated in order to eliminate the anisotropy in strength of laser metal deposited Ti−6Al−4V alloy by tensile tests, optical microscopy, scanning electron microscopy, electron back-scattered diffraction analyses and transmission electron microscopy. With increasing applied voltages from 0 to 130 V, the evolution of microstructure within columnar β grains followed the sequence of α′ martensite → colony α structure → basket-weave α structure. The electropulsing treated at 130 V weakened the texture of martensite within β grains. The as-built Ti−6Al−4V alloy showed an anisotropy in yield strength (6.2%). After processing at 130 V, the anisotropy in yield strength was reduced to 0.6%, which was attributed to the almost equivalent distribution of Schmid factor in the samples deformed along different orientations.

Effect of electropulsing treatment on the recovery of AZ31B magnesium alloy

Electropulsing treatment (EPT) is a potential annealing method with advantages of performance improvement and equipment simplification. In the current paper, the effect of EPT on the recovery of AZ31B magnesium alloy during a two-stage plastic deformation process was studied. The tensile properties, residual stress, microstructure, and recovery kinetics were evaluated. The residual stress decreased and the cumulative elongation increased slightly, whereas the yield strength retained relatively high after EPT. A typical recovery process was observed. Moreover, the recovery kinetics was accelerated by the improved pulse current density, which led to lower residual stress and higher cumulative elongation. Thus, satisfactory recovery can be achieved by adjusting the pulse current during EPT. Analysis of the full width at half maximum (FWHM) and kernel average misorientation (KAM) indicated that the dislocation density decreased after EPT. Therefore, the pulse current has a significant impact on the dislocation mobility and annihilation, accounting for the recovery behavior of AZ31B magnesium alloy. A model of the recovery kinetics was established to demonstrate the effect of the pulse current on recovery evolution in AZ31B magnesium alloy.

Mechanical Properties and Microstructure Evolution of Pre-stretched Aluminum Alloy After Induced Electro-Pulsing Treatment

Mechanical Properties and Microstructure Evolution of Pre-stretched Aluminum Alloy After Induced Electro-Pulsing Treatment

Effect of electropulsing on the solidification of mould flux

The effect of electropulsing on the microstructure formation in solidification of mould flux has been investigated. Experimental characterization and image analysis reveals that the electropulsing treatment reduces 46% porosity and increases the interfacial perimeter to area ratio by 100%. The latter provides strong evidence that electric current influences interfacial energy. Dendrite arm spacing is reduced considerable. Electropulsing promotes the anisotropic crystal growth and retards the formation of interconnected crystal network. The latter is favourable to the current flow, liquid refilling and lubrication. The work demonstrates that electropulsing can be used to modify the microstructure of slag and hence to control the horizontal heat transfer rate in the mould, which is desirable in continuous casting of advanced high strength steels.

The use of electropulse treatment of agricultural plants for various diseases

The paper considers measures to combat diseases spread by nematode viruses that infect the root system of tomatoes and cucumbers grown in closed ground and sown areas of the Republic of Uzbekistan, by installing electrical impulse discharges. The use of electropulse treatment is discussed, which does not affect the cost of harvesting, i.e. this technology does not have the results of dangerous consequences, but on the contrary, that the method of electropulse treatment effectively fights against carriers of the disease with worms. The results of experimental studies of the treatment of pathogenic plants with electropulse current discharge are analyzed, recommendations for the use of this technology are given.

Microstructural evolution and precipitate behavior of an AZ61 alloy plate processed with ECAP and electropulsing treatment

Electropulsing treatment processing (EPT)-induced microstructural evolution and precipitation behaviour of the β-Mg17Al12 phase in the AZ61 alloy were investigated by using scanning electron microscopy, X-ray diffraction and electron backscattering diffraction patterns. The results revealed that the EPT method is efficient in achieving a near-spherical Mg17Al12 phase (approximately 300 nm) and uniform ultrafine-grained structure (approximately 900 nm) featuring a weakened texture in AZ61 alloy plates after EPT for 40 μs-3 min. The improved structural characteristics are attributed to the rapid recrystallization and grain refinement induced by EPT at lower temperatures and in a short time. On this basis, kinetics analysis of the spheroidization and the dissolution of the β-Mg17Al12 precipitation phase and grain refinement and growth in the samples after EPT were performed. Furthermore, the mechanism of precipitation phase transformation and grain refinement during EPT was discussed.