A novel approach of high-voltage low-current electric energy input to synthesise cost-effective ultra-strong ductile material

ABSTRACT

Adopting a unique electrical circuit design, here we treat a significant low-cost engineering material (eutectoid steel not containing costly alloying elements) with a high-voltage (100 kV) low-current (150 mA) energy input (energy level exceeding cohesive energy). A distinctive structural evolution is ascertained with treatment duration of only 5 min as an outcome of lamellar fragmentation and matrix supersaturation. This envisages an origin of dispersed nano-sized hard cementite spheroids embedded in nano-thick martensite crystals of stratified-tile-morphology along with distributed α-ferrite regions containing sub-microscopic cementite particles of various shapes. Apart from the conjoint effect of nano-scale dispersion strengthening and martensitic strengthening overhauling the effect of conventional lamellar strengthening on a gross scale; high dislocation density and systematically arranged dislocations of similar sign at incoherent cementite particle-matrix interface provides a unique combination of ultra-high strength (UTS ∼ 1.5 GPa), significantly high specific strength (188 MPa/g cm⁻³) and large ductility (%Elongation = 20). Therefore, in terms of the adopted synthesis route, structural evolution and mechanical property achieved, a new dimension is hereby added to the next-generation material development so as to meet the ever increasing demand for low-cost structural application. In turn, we elucidate a fundamental conceptualization for the first time which exemplifies disproportionate atomic migration at highly incoherent nano-sized cementite particle-martensite matrix interface in steel under high-voltage low-current energy input, resulting in accumulation of dislocations of similar sign so as to significantly enhance strength along with retention of substantial ductility.

KEYWORDS:

• Material development
• high-voltage low-current energy input
• lamellar fragmentation and matrix supersaturation
• nano-scale structural strengthening
• unique combination of mechanical properties

Acknowledgements

No external funding source is utilised for carrying out this research work. Authors are thankful to the Director, National Institute of Technology Durgapur, India, for necessary administrative support.

Disclosure statement

No potential conflict of interest was reported by the author(s).