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research papers
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, (01)Al||(101)p and [011]Al||[01]p; (11)Al||(010)p and [011]Al||[01]p; (12)Al||(010)p, (101)Al||(100)p and [1]Al||[001]p; (1)Al||(010)p and [112]Al||[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.