As an important type of advanced cast irons, compacted graphite iron (CGI) received much attention because of its great wear resistance, thermal conductivity and high strength. Wide applications of CGI include pipes, machinery, cylinder heads and engine parts in the automotive industry. CGI is a metal matrix composite, composed of two phases in microstructure - graphite inclusion and metallic matrix. During manufacturing and application in automotive engines, CGI experiences severe working conditions such as high temperatures and pressures. So, a mismatch of thermal expansion between two phases, leading to interfacial debonding (graphite-matrix debonding), further formation of microcracks and their coalescence resulting in macrocracks and total failure, is considered as the main fracture mechanism of CGI. The interfacial debonding phenomenon in various composites under mechanical or thermal loads was investigated at microscale in different studies, but it still needs further study for CGI with its complex microstructure [1,2]. To assess the effect of thermal expansion of the two phases on thermal performance of CGI, this work generated a set of 3D numerical microstructural models. In each unit cell, a matrix cube contains a single graphite inclusion. Both graphite and matrix were assumed to display elastoplastic behaviour. Pure thermal loads were applied to models in finite-element analysis. The obtained results showed a relationship between the mismatch in thermal expansion of the two phases and thermomechanical behaviour of CGI.

References

[1] F.J. Rodriguez; A.D. Boccardo; P.M. Dardati; D.J. Celentano; L.A. Godoy; Finite Elements in Analysis and Design, 2018, 141, 26-36.

[2] M. Cao; E.N. Palkanoglou; K.P. Baxevanakis; V.V. Silberschmidt; Procedia Structural Integrity, 2022, 42, 777-784.