Room temperature control of grain orientation via directionally modulated current pulses

Abstract

Traditional approaches to control the microstructure of materials, such as annealing, require high temperature treatment for long periods of time. In this study, we present a room temperature microstructure manipulation method by using the mechanical momentum of electrical current pulses. In particular, a short burst of high-density current pulses with low duty cycle is applied to an annealed FeCrAl alloy, and the corresponding response of microstructure is captured by using Electron Backscattered Diffraction (EBSD) analysis. We show evidence of controllable changes in grain orientation at specimen temperature below 28 C. To demonstrate such microstructural control, we apply the current pulses in two perpendicular directions and observe the corresponding grain rotation. Up to 18 of grain rotation was observed, which could be reversed by varying the electropulsing direction. Detailed analysis at the grain level reveals that electropulsing in a specific direction induces clockwise rotation from their pristine state, while subsequent cross-perpendicular electropulsing results in an anticlockwise rotation. In addition, our proposed room temperature processing yields notable grain refinement, while the average misorientation and density of low-angle grain boundaries (LAGBs) remain unaltered. The findings of this study highlight the potentials of 'convective diffusion' in electrical current based materials processing science towards microstructural control at room temperature.

Elimination of Low-Angle Grain Boundary Networks in FeCrAl Alloys with the Electron Wind Force at a Low Temperature

“…Grain rotation, a common phenomenon associated with electropulsing [36,51], was evident in our study. In our analysis of the texture evolution through pole figure examinations in Figure 8, we noted a more prominent change in the HCP phase compared to the BCC phase during electropulsing.…”

“…These experiments aimed to measure changes in hardness and reduced modulus resulting from the treatments. The selection of processing parameters, such as current density, pulse width, and frequency, was made strategically, drawing upon our extensive experience with similar materials, as detailed in our prior work [36]. The pulse width was deliberately kept short at 40 microseconds, ensuring the sample receives a concise energy input, allowing ample time between pulses for heat dissipation and thus maintaining EWF as the dominant influencing factor.…”

“…By employing low frequency and narrow pulse widths, we successfully minimize thermal effects, maintaining the average temperature below 100 • C, even at an elevated current density of 3.35 × 10 5 A cm 2 . The use of short pulse width and low frequency provides sufficient time for heat to dissipate before the next pulse, minimizing the risk of excessive Joule heating [25,36,37]. This approach offers a more controlled exploration of how electropulsing can be optimized to exploit the beneficial aspects of EWF while mitigating the potential drawbacks of excessive Joule heating, thereby advancing our ability to distinguish between the thermal and athermal contributions to stress mitigation in electropulsing treatments.…”

Effect of High Current Density Pulses on Performance Enhancement of Optoelectronic Devices

“…Likewise, when applying current pulsing to diverse materials and alloys, significant enhancements were observed with pulse durations of less than one minute 29 and 2 min. 36 These findings underscore the effectiveness of shorter pulsing durations in instigating favorable changes in device characteristics. The 180 s pulsing scheme is used in this study just to make sure that a steady-state has been reached.…”

Rejuvenation of degraded Zener diodes with the electron wind force

“…Such a regimen ensures that thermal spikes are only transient and given ample time to dissipate, thus maintaining the processing temperature in ambient range. 30,31) The fundamental to this technique is the exploitation of the EWF, a mechanical phenomenon emanating from the momentum loss of electrons upon their interaction with lattice defects. In contrast to traditional electropulsing methods that predominantly rely on Joule heating and its associated thermal consequences, 32,33) our strategy capitalizes on the EWF to circumvent thermal effects, offering an efficient paradigm in defect mitigation and device rejuvenation.…”