As a follow-up to our previous work, the 2D transient Multiphysics electrothermal-mechanical and metallurgical model of a 1.2kV-80mOhm gate-planar SiC MOSFET power chip in a single FEM software, created previously by the authors, has been developed. This model aims to quantify the short-circuit (SC) critical time and energy density of attaining the local dielectric interlayer (ILD) strength and the Al source-metal solidus-liquidus phase transition at elevated temperatures. The novelty of this extended model is considering non-linear electrothermal and elastoplastic material property laws over a wide range of temperatures. Repetitive experimental SC events were carried out to verify the gate-aging occurrence in accordance with the critical values extracted from the proposed model.