Influence of High-Current-Density Impulses on the Compression Behavior: Experiments with Iron and a Nickel-Based Alloy

Demler, Eugen; Gerstein, Gregory; Dalinger, Andrej; Epishin, Alexander; Rodman, Dmytro; Nürnberger, Florian

doi:10.1007/s11665-016-2457-x

Cited by 8 publications

(10 citation statements)

References 12 publications

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“…Compression experiments with and without electric current pulsing during deformation were performed at a deformation rate of 0.1 mm/min using a Walter & Bai 100 universal testing machine at the Institute of Materials Science, Leibniz University Hannover. After the application of a pre-force of 80 N and an offset time to ensure proper electrical contact, electric current pulses of 7 kA, 55 V and a duration of 0.5 ms were applied every second using a high current impulse generator (further information regarding the high current impulse generator are available in [32]). The resulting current densities amounted to 1.66 ± 0.01 kA/mm 2 when considering the contact area prior to deformation.…”

Section: Experimental Procedures 21 Macroscopic Electroplasticity Exmentioning

confidence: 99%

Investigation of the electroplastic effect using nanoindentation

et al. 2019

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A promising approach to deform metallic-intermetallic composite materials is the application of electric current pulses during the deformation process to achieve a lower yield strength and enhanced elongation to fracture. This is known as the electroplastic effect. We developed a novel setup to study the electroplastic effect during nanoindentation on individual phases and well-defined interfaces. Using a eutectic Al-Al2Cu alloy as a model material, we compare the electroplastic nanoindentation results to macroscopic electroplastic compression tests. The results of the micro-and macroscopic investigations reveal current induced displacement shifts and stress drops, respectively, with the first displacement shift / stress drop being higher than the subsequent ones. A higher current intensity, higher loading rate and larger pulsing interval all cause increased displacement shifts. This observation, in conjunction with the fact that the first displacement shift is highest, strongly indicates that de-pinning of dislocations from obstacles dominates the mechanical response, rather than solely thermal effects.

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Section: Experimental Procedures 21 Macroscopic Electroplasticity Exmentioning

confidence: 99%

Investigation of the electroplastic effect using nanoindentation

et al. 2019

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“…This led to a visible forming-relief on the specimen's polished surface, which indicated that additional deformation mechanisms were activated by dislocation slip on the {111} plane. Similarly, a drop in yield strength was observed upon application of high current density pulses during compression of single crystal nickel-based alloy PWA 1480 13 . In this case, the microstructural analyses indicated a redistribution of dislocations.…”

Section: Introductionmentioning

confidence: 83%

“…The specimens were placed between an upper and a lower electrode, which were connected to a high-current impulse generator featuring high capacitance-condensers and short switching times. The duration of the current-impulse that could be periodically introduced into the specimen was varied from 0.1 to 1 ms at a current strength between 3 and 10 kA 13 . Ceramic insulation plates were employed and a high-speed infrared camera (FLIR ThermaCam SC 3000) was used to monitor the specimen temperature at a maximum frequency of 750 Hz with a thermal sensitivity of 0.02°C at 30°C.…”

Section: Impulse Treatmentmentioning

confidence: 99%

“…Since the different mechanisms of the electroimpulserelated hardening and softening observed in the previous investigations are not yet understood in the nickel-based superalloy 12,13 , the objective of the present study was to shed light on the relationship between application of the high current density pulses and dislocation motion in different microstructural states. These tests were conducted at constant mechanical stresses, which were well below the material-specific compression limit.…”

Section: Introductionmentioning

confidence: 99%

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Influence of High Current-Density Impulses on the Stress-Strain Response and Microstructural Evolution of the Single Crystal Superalloy CMSX-4

et al. 2018

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Owing to the low formability of single-crystal nickel-based materials, single-crystal components are typically cast. Subsequently, a multi-stage heat treatment is carried out in order to partially compensate the dendrite segregation and to stabilize the precipitated γ'-phase. Such components possess a high resistance to creep at elevated temperatures. Since it is known that electrical impulses can be used to increase the formability of various materials, the potential of an electrical high current-density impulse treatment was evaluated for forming of the high strength nickel-based superalloy CMSX-4. Heat treated and pre-deformed specimens were loaded in compression and subjected to short pulses with a high-current density of 2.3 kA/mm 2. Depending on the microstructural state, the material demonstrated work hardening or softening as a consequence of the impulse treatment. In addition, experiments were carried out on crept specimens to test whether the current-impulse treatment can be used to reverse creep-related segregation of alloying elements (raft formation). It was possible to observe a change in the concentration of the elements in the γ/γ'-phase transition following the currentimpulse treatment. In particular, a local increase in the γ-forming elements Cr, Co and a decrease in the γ'-forming elements Ta, Ti was observed after the impulse treatment.

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“…To investigate the influence of the electroplastic effect on the microstructure evolution, samples of both materials were treated in a special testing machine that allows to employ high current impulses parallel to the mechanical load direction. The equipment was described by Demler et al [21]. In order to avoid a strong voltage drop during the impulse, double layer capacitors are used as the energy source.…”

Section: Methodsmentioning

confidence: 99%

Visualization and Observation of Morphological Peculiarities of Twin Formation in Mg-Based Samples After Electrically Assisted Forming

Reschka

Gerstein

Dalinger

et al. 2019

Metallogr. Microstruct. Anal.

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By using electrically assisted forming the usually rather poor workability of magnesium can be improved. The processes taking place during these forming operations have a strong influence on the microstructure. However, the metallographic preparation of magnesium is challenging due to its low hardness and strong tendency to oxidize. Therefore, a reliable preparation method was developed that revealed the microstructural features caused by the electrically assisted forming. The different morphologies of twins caused by plastic deformation and of those caused by an electric impulse could clearly be distinguished.

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Influence of High-Current-Density Impulses on the Compression Behavior: Experiments with Iron and a Nickel-Based Alloy

Cited by 8 publications

References 12 publications

Investigation of the electroplastic effect using nanoindentation

Investigation of the electroplastic effect using nanoindentation

Influence of High Current-Density Impulses on the Stress-Strain Response and Microstructural Evolution of the Single Crystal Superalloy CMSX-4

Visualization and Observation of Morphological Peculiarities of Twin Formation in Mg-Based Samples After Electrically Assisted Forming

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