Abstract
This work provides a critical assessment of electric effects on the microstructure evolution at the heat-affected zone in electric arc welding. Electric effects are the interactions between electromagnetic fields and materials’ microstructures. They differ from the arc effect and the Joule heating effect by providing an alternative contribution to nucleation, grain growth, recrystallisation and tempering. The influence of the electric effect on grain size, defects, anisotropic properties, precipitates and residual stress has been examined kinetically and thermodynamically. The use of adaptable electric current densities, pulse durations, pulse frequencies and electrode movements is suggested to achieve desirable microstructures and mechanical properties for the weldments.
Highlights
Electric arc welding (EAW) utilises an electric current between 100 and 1000 A to generate the electric arc
Recrystallisation is a microstructural relaxation driven by the second law of thermodynamics in a minimisation of the system’s free energy without a phase transition [42]
Spheroidized nanoscale FeC3 particles are seen throughout the image, while the original microstructure before recrystallisation was a deformed lamellar pearlite6.oIft1i1s not possible to form such fine grains by rearrangement of the interface energy alone
Summary
Electric arc welding (EAW) utilises an electric current between 100 and 1000 A to generate the electric arc. The electric effect is different from the heat effect The former is associated with an electromagnetic interaction and is described by Maxwell’s equations. Despite the gradual reduction of the current density from the electrode across the HAZ to the matrix, due to the incrementation of the cross-section perpendicular to the current flow direction, the electric effects on liquid. Despite the gradual reduction of the current density from the electrode across the HAZ to the matrix, due to the incrementation of the cross-section perpendicular to the current flow direction, the electric effects on liquid metal, grain gmroewtatlh, g, rreacinrygsrtaolwlisthat,iroencraynsdtatlelimsapteiorinnganndeetdemtopebreinagssneseseeddtcoribtiecaalslsye.sTshede acirmiticoafltlhy.isTahretaicimle owfatshtisoacrotnicdleucwtassutcohcaonnadsuscetsssmucehnat ninaosrsdesesrmtoenptroinviodredearctoompprorevhideensaivcoemunpdreehrsetnasnivdeiunngdoefrtshtaenmdiencghaonf itshmesmthecaht aanffiescmt sthtehamt iacfrfoescttrtuhcetumriecsroosftwruecltdumreesnotsf wbeeyldonmdenthtse bheeyaot nefdfetchte. The change of electric current free energy, according to Equation (2), is dependent on the average current density square, the change in the electrical conductivities due to the microstructural evolution and the volume of materials. As discussed earlier in the present work, the kinetic effect of the electric current expedites the process and makes the material’s microstructures evolve quickly along the new thermodynamic trend
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