The Sequence of Intermetallics Formation during the Solidification of an Al-Mg-Si Alloy Containing La

Abstract

A mechanism by which La modifies the Fe-bearing intermetallics in a 6xxx series Al alloy is examined using calorimetry. Thermal events accompanying the formation of various phases are identified by establishing a correspondence between them and microstructures of as-cast alloys. It is concluded that a previously suggested surface adsorption mechanism is unlikely to be operative. During solidification, the addition of lanthanum results in the formation of the La(Al,Si) 2 phase and the depletion of the remaining melt of Si. It is hypothesized that the decreased Si/Fe ratio in the melt caused by the presence of La favors the formation of the a-AlFeSi phase, which is less detrimental to the formability of the alloy than the b-AlFeSi phase.

Microstructural Evolution and Solidification Behavior of Al-Mg-Si Alloy in High-Pressure Die Casting

“…The solidification of Al-Mg (-Si)-based alloys has been the subject of many studies, but most of them fall into the category of wrought alloys [12,13] or high silicon (>5 wt pct Si) and low magnesium (<1 wt pct) cast alloys (e.g., A356) [14,15] produced by sand casting or gravity die-casting process. Previous studies were rather limited in describing the solidification and microstructural evolution of high magnesium (>4 wt pct) and silicon (>1.5 wt pct) cast alloys in HPDC process.…”

Development and characterization of low-silicon cast aluminum alloys for thermal dissipation

“…In the high Mg-content alloy (Al-1.5Mg-1Fe-0.5Si alloy), it is likely that the incorporation of Si atoms into the Mg 2 Si phase enables a-AlFeSi phase to crystallize even in the interdendritic regions between secondary dendrite arms under the same casting condition. Hosseinifar and Malakhov [45] have reported a similar example of phase selection in a 6xxx Al alloy: the addition of La resulted in the formation of La(Al,Si) 2 phase and a decrease in the Si/Fe ratio in the eutectic liquid, favoring the crystallization of a-AlFeSi rather than b-AlFeSi phase. Table 5 lists characteristic solidification parameters, namely the solidification temperature range, DCP, the first intermetallic crystallization point (FICP), and the coherency temperature range between DCP and the end of solidification, calculated from the CCA experiments.…”

The sequence of intermetallic formation and solidification pathway of an Al–13Mg–7Si–2Cu in-situ composite

“…Once a solid substance is formed, it cannot react with the remaining liquid and diffusion cannot take place. In other words, previously formed solid entities change neither during the solidification nor after the process is completed [19]. It can be seen that the irregularly shaped black particles were surrounded by quenched liquid.…”