Atomic scale investigations of carbon-based cathode materials deformation mechanism during aluminum electrolysis

The creep strain of full graphitic cathode blocks has been measured with a laboratory cell. The creep tests were performed three times under extern load 2-6 MPa and at temperature of 950 degrees C for 15 min, 50 min and 100 min respectively after starting the electrolysis. The deformation mechanisms in the carbon cathodes for aluminum electrolysis have been comprehensively studied at the atomic scale by high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The microstructural observation confirms that the governing deformation mechanism for the carbon cathode is basal plane dislocation pile-ups and dislocation tangles at the stage of transient creep. Microstructure rearrangement of the carbon cathode including deformation bands, rotating, delamination and propagation of microcracks deteriorates its creep resistance at the stage of steady-state creep. The deformation of carbon cathodes is closely correlated with the accumulation and amorphization of the graphite during aluminum electrolysis.