Morphology of intermetallics tailoring tensile properties and quality index of a eutectic Al-Si-Ni alloy

Abstract

Herein, the eutectic Al–11 wt% Si–5 wt% Ni alloy, directionally solidified under transient heat‐flow conditions, is comparatively evaluated in relation to the binary Al–11 wt% Si and Al–5 wt% Ni alloys. Correlations are developed relating the solidification cooling rate, primary dendritic spacing, and tensile properties. The Al3Ni intermetallic compounds (IMCs) are shown to have a morphological transition from plate‐like to fishbone for Ṫ < 6 °C s−1. Experimental Hall–Petch‐type equations are proposed relating yield and ultimate tensile strengths to λ1. Moreover, both the quality index (QI), which depends on the determined tensile properties, and the fishbone/plate‐like ratio (FPR) of the Al3Ni IMCs are plotted simultaneously as a function of Ṫ. This procedure permits three different regions to be determined relating solidification operational parameters to microstructural features and a quality parameter, according to the morphologies of the Al3Ni IMCs, namely (I) plate‐like, (II) fishbone rising, and (III) fishbone prevalence