Influence of κ-carbide interface structure on the formability of lightweight steels

Abstract

Abstractκ-carbide () in high aluminium (Al) steels is grown from austenite () via + or α+ ( represents ferrite), and is a lamellar structure. This work demonstrates that the formability of high Al lightweight steels is affected by the lattice misfit and interface shape between  and matrix. The cold workability can be improved by either to change the steel chemical constitution or to implement an electro-thermo-mechanical process. For ferrite-matrix-based high Al steel, electric-current promotes the spheroidization and refinement of  structure and reduces volume fraction of  phase. This retards the crack nucleation and propagation, and hence improves the materials formability. The observation is caused by a direct effect of electric-current rather than side effects.

Inclusion agglomeration in electrified molten metal: Thermodynamic consideration

“…[8][9]28 The average current density across the liquid metal is calculated to be around 6.6710 6 A/m 2 . Two identical spherical inclusions with radius of 2 mm are introduced into the matrix.…”

“…They are based on the electron-phonon interaction, 15,16 electron-dislocation interaction, 17,18 collective motion approximation, 19,20 thermodynamic consideration, 21,22 respectively and so on. Experimental investigation has provided very rich evidences on using electric current to affect microstructure, 23,24 crystallographic taxture, 25,26 workability, 27,28 and processing environments. 29,30 In the present work, thermodynamic consideration is implemented to investigate the inclusion agglomeration behaviour under electric current.…”

Computation of electromagnetic field and complex materials interaction

“…The electrical resistance of the sample without inclusion is 2.5×10 −4 Ω. The average electric current density is 2.0×10 9 A·m −2 , which is in the same order as that used in many electropulsing processing experiments [12,13] but is at least 3 orders of magnitude smaller than the current-induced magnetization switching [14]. An electrically neutral inclusion with radius r i and electrical conductivity σ i = ησ m is embedded in the metal matrix with its centre in the distance from the centre of the matrix vertically (Fig.…”

Stability of martensite with pulsed electric current in dual-phase steels

“…Eventually, ultrafinegrained ferrite matrix within tempered martensite regions are produced by using EPT. In addition, the phase transformation (decomposition of martensite to ferrite and cementite) associated with Gibbs free energy change can also be affected by EPT at a temperature about 685 o C due to different electrical conductivities [28][29][30][31][32]42]. It is well known that the Gibbs free energy of whole system (steel) contains four typical components: chemical free energy, interface energy…”

“…(grain boundary and phase boundary), strain-induced energy and current free energy when an electrical current going through the steel specimen [42]. Due to different electrical conductivity of phases existed in steel, the current free energy can be changed subsequently by EPT.…”