A thermomechanical constitutive model for phase transformations in silicon under pressure and contact loading conditions

Most of the technologically relevant abrasive machining techniques for silicon (Si) such as lapping, sawing and grinding are based on the interaction of the silicon surface with a hard particle or asperity. It has been long established that the governing deformation mechanism for Si under such contact loading conditions is stress induced phase transformation. The present work introduces a novel phenomenological constitutive model for phase transformations of silicon set up in a thermomechanical framework of broad applicability. Taking into account experimental observations as well as first principle and molecular dynamics calculations, it captures both the cd-Si → β-Si transition upon compression and the β-Si → a-Si transition upon rapid decompression, which are most relevant for indenter loading. The model was numerically implemented in analogy to incremental plasticity and successfully applied for finite-element (FE) simulations of nanoindentation.