3D Architecture and Load Partition in Eutectic Al‐Si Alloys

Abstract

The changes of the three dimensional architecture of a eutectic AlSi12 alloy during heat treatment are revealed by means of synchrotron holotomography. The non‐destructive nature of the holotomography technique allows to analyze the same volumes in different thermal conditions. The results show a disintegration of the interconnected eutectic Si‐lamellae into isolated elongated particles. The load carrying capacity of both types of Si morphologies is studied by in situ neutron diffraction during compression tests. The experimental results are compared to those obtained using a micromechanical model developed for metal matrix composites based on a homogenization approach. The correlation between experiments and calculations shows that the interconnectivity of Si must be considered to account for the strength exhibited by the eutectic alloy. The present study bridges the gap between the already available two‐dimensional studies of architecture and properties of the binary AlSi12 alloy and new three‐dimensional studies of more complex systems based on this alloy.

Characterisation of 3D strain heterogeneity at the microstructure scale during low cycle fatigue of an AlSi7Cu3Mg alloy at 250 °C

“…The same trend was observed at 250°C. Considering that large particles are more likely to belong to networks than smaller particles of larger sphericity, this observation could agree with those of Requena et al [64] who find that an interconnected Si phase can withstand larger stress, hence a larger strain, than a Si phase whose interconnectivity has been destroyed by heat treatment. It was not possible to evidence any influence of particle/network orientation.…”

Sub-micrometre holotomographic characterisation of the effects of solution heat treatment on an AlMg7.3Si3.5 alloy

“…The elevated temperature strength and the hardness of the material decrease after the solution heat treatment in a similar way as reported for eutectic Al–Si alloys [13]. The alloy in as-cast condition as well as after solution treatment was tested in an overaged condition (2 h/300 °C), to minimise precipitation strengthening.…”

The role of intermetallics in stress partitioning and damage evolution of AlSi12CuMgNi alloy

“…However, the presence of IM phases strongly influences the microstructure: Fig. 10 shows the evolution of the von Mises equivalent stress of the aluminum, silicon and IM phases in the AlSi12CuMgNi alloy, obtained in this study, compared with that of the AlSi12 alloy (reported in [6]). The aluminum matriX yields at 50 MPa and 100 MPa in the AlSi12 [16] and AlSi12CuMgNi alloys, respectively.…”

“…It can be seen that our micromechanical model well predicts stresses, in both Al and Si phases. On the contrary, the model proposed by Requena et al [6] for the AlSi12 alloy, in which internal damage of Si was not considered, underestimated stresses induced by the applied compressive stress. The latter result gives confidence in the model developed above, and opens routes for further investigation of theses alloys: the use of in-situ CT would better disclose the evolution of damage in IM and Si particles, thereby allowing perfecting the model.…”