Self-healing of damage inside metals triggered by electropulsing stimuli

Abstract

The microscopic defects that distributed randomly in metals are not only hard to detect, but also may inevitably cause catastrophic failure. Thus, autonomic probing and healing for damage inside metals continue to be a challenging. Here we show a novel approach for self-healing using electropulsing as a stimulus to trigger repairing of damaged metals. This is achieved via a process that through expelling absolutely currents, the microcrack causes them to be redistributed to form a concentrated and a diluted region around it, thereby inducing an extremely high temperature gradient and a large compressive stress, which drive material flow to close microcracks. Simultaneously, a large enough heat for bonding atoms was produced. That is, the microcrack as an empty cavity can be regarded as a special micro-device to shape a localized microscopic energy field, which in turn activates a healing process. The microstructure and mechanical property verified the extrinsic self-healing of a titanium alloy. The process is performed on a short timescale, is enable to detect automatically and act directly on the internal defects in metals, and to heal damage without any healing agent, long time heating as well as applied high pressure, offering unique advantages over conventional healing approaches.

Advanced Materials for Next‐Generation Spacecraft

“…Titanium alloys play a key role in many space applications, ranging from parts of rocket engines to structural elements of spacecraft and man habitat systems. Figure c,d illustrates similar approaches for healing cracks in the Ti–6Al–4 V alloy at a relative low temperature, with rapid, efficient recrystallization and microcrack healing, and self‐healing of cracks in the TC4 titanium alloy under actions of electropulsing stimuli . It should be noted that healing of microcracks in metal alloys, i.e., in electric conductors, involves a wide spectrum of physical effects.…”

“…d) Self‐healing of damage inside the TC4 titanium alloy triggered by electropulsing stimuli. Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International License . Copyright 2017, The Authors, published by Springer Nature.…”

Self‐Healing Phenomena in Metals

“…An alternative approach to use electric field was adopted by Song and co‐workers, who demonstrated that internal cracks in a titanium alloy could be healed by electropulsing using the discharge of a capacitor to generate a current through the metal specimen. Around cracks the current is locally enhanced as the flow is concentrated, which leads to a resistive heating at the edges of the open‐volume defect.…”

Low‐Energy Room‐Temperature Healing of Cellular Metals

“…Metals, therefore, are healed at temperatures near or above their melting points, which requires high temperatures and large amounts of energy (10 7 to 10 9 J per 1 mm crack length for solute precipitation, for example) . Strategies using low melting temperature alloys (10 2 to 10 3 J mm −1 ), highly localized joule heating (10 2 to 10 4 J mm −1 ), and combined solute diffusion and phase transformation (10 6 to 10 7 J mm −1 ) have been developed to reduce the healing energy input, but none have demonstrated effective room‐temperature healing.…”