Twin-controlled growth of eutectic Si in unmodified and Sr-modified Al–12.7%Si alloys investigated by SEM/EBSD

Silicon Nitride Whisker-Reinforced Aluminum Matrix Composites: Twinning and Precipitation Behavior

“…The addition of Si 3 N 4 whiskers led to a refined Al-Si eutectic structure and primary α-Al dendrites [52], since the morphology of Al-Si eutectic structure was changed from network-like to particulate [42]. It has also been shown that the silicon in the Al-Si cast alloys formed a continuous network, and twinning is an important branching mechanism [44,[54][55][56]. Figure 1a is a secondary electron (SE) image showing typical microstructures of the Al-11.5Si-1.0Mg-0.5Cu-0.5Ni, and Figure 1b is a SE image showing typical microstructures of the Si 3 N 4w /Al-11.5Si-1.0Mg-0.5Cu-0.5Ni composite.…”

Chemical modification of degenerate eutectics: A review of recent advances and current issues

“…The poisoning of the TPRE mechanism has also been used recently to explain the EBSD results of Liu et al on a Sr-modified Al-Si alloy. 67 The authors suggested that modification via poisoning can occur in two distinct ways: Sr can block the Si growth on one initial {111} twin plane and force the formation of (i) new twins with the same misorientation and inclination as the first, or (ii) new twins with different orientations and inclinations. The latter scenario leads to a change in the growth direction, resulting in a more isotropic growth and thus the appearance of "quasi-equiaxed" Si crystals.…”

“…The latter scenario leads to a change in the growth direction, resulting in a more isotropic growth and thus the appearance of "quasi-equiaxed" Si crystals. 67 The authors suppose that due to this Sr-induced deceleration of the Si crystal in the original growth direction, the growth velocities of both eutectic phases become comparable, i.e., Si no longer leads at the growth front. However, this conclusion is impossible to verify through ex situ experimental probes like EBSD.…”

Effect of Trace Yttrium Addition and Heat Treatment on the Microstructure and Mechanical Properties of As-Cast ADC12 Aluminum Alloy

“…However, as the Y addition amount increased to 0.3 wt%, the mean area and length-width ratio of the eutectic Si phase exhibited a slight increase. According to the impurity-induced twinning mechanism (IIT) [13][14][15][16] and the restricted twin plane reentrant edge growth mechanism (TPRE) [17], the modified Y atoms easily concentrate near the Si solid-liquid interface or Si grooves. This phenomenon may change the growth mode and eventually lead to the isotropic growth of grain.…”