Three-dimensional study of Ni aluminides in an AlSi12 alloy by means of light optical and synchrotron microtomography

摘要

The three-dimensional (3D) microstructure of an AlSil2Ni alloy in as-cast and in solution-treated conditions is characterized by light optical and synchrotron tomography. Eutectic Al-Si alloys containing 1 wt. percent Ni in as-cast condition present networks of connected Si lamellae as well as complex 3D shapes of Ni-containing aluminides. The eutectic Si networks disintegrate during solution treatment in the binary Al-Si alloy while they remain connected in the Al-Si-Ni alloy. The contiguity between eutectic Si and Ni-containing aluminides is maintained, when the alloy is solution treated at 540 deg C for 24 h. The sphericity of the aluminides is only slightly increased by the solution treatment. The reinforcing role of eutectic Si together with the Ni-containing aluminides is governed by a stable interconnectivity and contiguity of these rigid phases accumulating approx 20 vol. percent. The 3D data obtained by synchrotron tomography quantify connectivity, shape and volume fraction of eutectic Si and aluminides, whereas their contiguity is verified by light optical sectioning tomography.