The orientation relationships and growth mechanism of rectangle-like dispersoids in an Al-Si-Mg-Hf alloy

The orientation relationships (ORs) between the matrix and the rectangle-like dispersoids formed at 560 o C for 20 h in an Al-Si-Mg-Hf alloy are characterized by transmission electron microscopy and selected area electron diffraction. Four ORs between the matrix and the dispersoids are identified as [112] Al //[010] d with (200) p deviating 3.21 o from (11-1) Al ; [012] Al //[010] d , (200) Al //(002) p ; [-113] Al //[010] d with (20-2) d deviating 6.77 o from (2-42) Al ; [-113] Al //[3-1-3] d , (220) Al //(130) d . Combined with the near-coincident site lattice distribution, it can be concluded that the deviation from the well-matched plane increases the interface energy of dispersoid/matrix interface, which inhibits the dispersoid growing along one-dimensional direction and presenting a rectangle-like morphology.