The orientation relationships of nanobelt-like Si2Hf precipitates in an Al–Si–Mg–Hf alloy

The orientation relationships (ORs) between the Al matrix and Si2Hf precipitates with an orthorhombic structure in an Al–Si–Mg–Hf alloy after heat treatment at 833 K for 20 h were investigated by transmission electron microscopy and electron diffraction. Four ORs are identified as (100)Al||(010)p, (0\overline {1}1)Al||(101)p and [011]Al||[\overline {1}01]p; (11\overline {1})Al||(010)p and [011]Al||[\overline {1}01]p; (12\overline {1})Al||(010)p, (101)Al||(100)p and [1\overline {11}]Al||[001]p; (\overline {11}1)Al||(010)p and [112]Al||[\overline {1}01]p. The habit planes of these four ORs are rationalized by the fraction of good atomic matching sites at the interface. In addition, the formation of Si2Hf precipitates with a nanobelt-like morphology is interpreted on the basis of the near-coincident site lattice distribution.

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