Growth related metastable phase selection in a 6xxx series wrought Al alloy

Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy

“…[1]) in experiment and this may arise either because soon after formation it was rapidly transformed to a-or b-AlFeSi (for which Figure 14 offers little support), or more likely that it was comparatively difficult to nucleate and grow Al 13 Fe 4 at the required rate so that once a-or b-AlFeSi were formed, it was kinetically preferred for the residual Fe-rich liquid to be transformed as further a-or b-AlFeSi, rather than through the nucleation of a new phase. [8,33] This agrees well with the modeling when the Scheil calculations were performed without the Al 13 Fe 4 phase (Figure 14(c)). The absence of the predicted much smaller fraction of a-AlMnSi (Eq.…”

“…An in-house developed calibration procedure was used for determining the relative weight fractions of a c -AlFeSi and b-AlFeSi from XRD data, more details of which can be found in references. [8,22,24] The extracted particles were further analyzed using a high-resolution field emission gun (FEG) SEM (JEOL 840F). The approach used to measure the IMCs inter-connectivity, length of petals, and length of longest facet side of platelets of the extracted particles was detailed in previous work.…”

“…[3,4] Previous studies show that a c -AlFeSi and b-AlFeSi are the two dominant Fe-IMCs in 6063 Al alloys. [5][6][7][8] 3D analysis of these Fe-IMCs after extraction from the primary a-Al using an Al dissolution approach revealed that a c -Al(FeMn)Si (from now referred to as a c -AlFeSi) had a dendritic-like morphology while b-AlFeSi had a plate-like morphology. [9] Among these IMCs, it has been noted that b-AlFeSi in particular, because of its more planar geometry, reduced the ductility of an Al alloy 6063.…”

“…For example the cooling rate and solid/liquid growth velocity in DC casting significantly affect the proportions of a c -AlFeSi and b-AlFeSi in the final microstructure. [8,10,21,22] But, since the cooling rate and growth velocity vary from position to position in the billet during DC casting, [2,23] the primary Al grain size and proportion of the Fe-IMCs and Mg 2 Si across the cross section of the billet also varies, which should be accounted for in homogenization heat treatment optimization. In this paper, we apply an IMC phase extraction technique, along with a series of other characterization methods, at different positions in a AA6xxx DC cast billet to track in detail changes in the Fe-rich IMC inter-connectivity, size, morphology, type, and proportion during homogenization.…”

Influence of Heat Treatment on the Surface Structure of 6082 Al Alloys

“…[1][2][3][4] The b-AlFeSi phase is an undesirable phase due to formation of hot cracking and surface defects during subsequent procedures, e.g., extrusion. [5,6] To obtain high surface-quality extruded products, at reasonable extrusion rates, the as-cast billets need to be homogenized before extrusion.…”