Thermomechanical behaviour and damage in CGI: 3D finite-element analysis

This paper studies graphite decohesion as the primary fracture mechanism in compacted graphite iron (CGI, EN-GJV-450) under thermomechanical loading. Despite widespread industrial applications of CGI and considerable research on its mechanical properties, its thermomechanical behaviour and related debonding remain incompletely understood, especially in terms of the influence of material's matrix phases. A series of finite-element models based on 3D unit cells constructed, featuring a single graphite particle represented as a sphere or oblate spheroid embedded in a metallic matrix. The inclusion is surrounded by an additional layer of either pearlite or ferrite, to investigate the impact of matrix phase on thermal debonding. The models are analysed with a finite-element approach assuming elastoplastic behaviour for all constituents. The proposed numerical strategy specifically studies the influence of matrix phases on thermal damage and the thermomechanical performance of CGI from room temperature to 400 °C or 500 °C, followed by mechanical loading of 400 MPa and cooling. The results obtained have the potential to enhance the understanding of CGI's response at microscale to thermal loads, thereby contributing to the comprehension of the thermomechanical behaviours of CGI at the macroscale.