Effect of local and global connectivity of phases on damage evolution in cast Al-Si Alloys

Abstract

The strength and damage behavior of Aluminum-Silicon piston alloys during external mechanical loading is determined by the mechanical and physical properties of the 3D architecture of Si and intermetallics, their thermal/mechanical stability and their geometrical arrangement (volume fraction, size, morphology, distribution, interconnectivity, contiguity), which may vary during production and service. The advance of modern characterisation methods that allow to observe the evolution of the microstructure in situ and/or three-dimensionally, provide new insights crucial for the case of complex microstructures. In this thesis, with the implementation of state of the art ex-situ and in-situ x-ray and synchrotron x-ray tomography methods complemented by 2D metallography investigations, microstructural features affecting strength and damage mechanisms during ambient and elevated temperature tensile deformation as a function of chemical composition and heat treatment were univocally identified. Also, a quantitative relationship between 3D architecture of the investigated Al-Si alloys and microstructural features affecting the damage processes during external loading could be established.