In-Situ and Real-Time Analysis of the Formation of Strains and Microstructure Defects during Solidification of Al-3.5 Wt Pct Ni Alloys

Abstract

Alloy solidification was investigated in situ and real time by using a unique experimental setup developed at the European Synchrotron Radiation Facility (ESRF) combining both synchrotron X-ray radiography and topography. Although synchrotron X-ray radiography enables the investigation of the solid-liquid interface of metallic alloys, white-beam synchrotron X-ray topography enables the investigation of the formation of strains and defects formation in the growing solid microstructure. In this article, we present results obtained during directional solidification experiments performed with Al-3.5 wt pct Ni samples. First, the initial state after thermal stabilization is characterized. Next, the interface morphological instability and the transition to the columnar growth regime are thoroughly investigated. Topography observation shows that several parts of each dendrite become disoriented while the microstructure is developing. Disorientations are quantified and the aluminum yield stress at the melting point is estimated from the bending of secondary arms. Last, coupled growth of eutectic and dendrites settles with the formation of the eutectic phase. The eutectic grains grow strained and the dendrites concomitantly undergo additional stress.

Origins of misorientation defects in single crystal castings: A time resolved in situ synchrotron X-ray radiography study

“…From an experimental perspective, deformation during solidification is difficult to observe and quantify [1]. From a modelling and simulation approach, the change in geometry as a result of solidification needs to be incorporated into flow and structural solvers.…”

“…This allows for direct observation of microstructures as solidification progresses. In particular, it has been used to examine dendrite fragmentation in aluminium alloys, a phenomena only previously accessible by post mortem characterisation [1].…”

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

“…Over the last decade, an increasing number of real-time X-ray imaging studies of solidification microstructures and phenomena in real metals have been reported, addressing a broad variety of topics such as dendritic growth, [20][21][22][23] coarsening, [24] morphological transitions, [23] dendrite fragmentation, [25][26][27] solute diffusion and convection, [22,28] and momentum transfer relations in eutectics [29] and monotectics. [30] Most of these, and other recent in-situ studies, have been carried out with high-brilliance synchrotron radiation, where X-ray absorption-and near-field phase contrast is combined to bring about 2-D or 3D time-resolved data.…”

“…[30] Most of these, and other recent in-situ studies, have been carried out with high-brilliance synchrotron radiation, where X-ray absorption-and near-field phase contrast is combined to bring about 2-D or 3D time-resolved data. [20][21][22][23][24][25][26][27]29,30] …”

Dendrite Bending during Directional Solidification

“…Particular research highlights have been the study of the role of solute build-up on remelting-driven fragmentation [12], the observa-tion of misorientations emerging during solidification [13,14], imaging eutectic solidification [15,16] and identifying the importance of granular behaviour in semi-solid alloys [17].…”