Orientational dependence of lathy ferrite in Fe–Cr–Ni alloy during directional solidification

The morphology and crystallography of lathy ferrite in a Fe–Cr–Ni alloy during solidification were examined by transmission electron microscopy (TEM). The formation mechanism of the parallel lathy ferrite during solidification was proposed based on the crystallography relationship between ferrite and austenite. It was found that the morphology of the lathy ferrite was determined by the crystallography. When the crystal plane in the substrate is (1¯10)γ, lathy ferrite grows in parallel and the crystallography relationship between lathy ferrite and austenite is (11¯1)δ∥(1¯10)γ, [211¯]δ∥[110]γ and [011]δ ∥ [001]γ. Under this condition, lathy ferrite is only preferentially elongated along [110]γ because the misfit of lattice spacing between [211¯]δ and [110]γ is relatively low. This preferential growth accounts for why parallel lathy ferrite can be observed in the solidified microstructure of the Fe–Cr–Ni alloy.

► Morphology and crystallography of the parallel lathy ferrite was revealed by TEM.
► When the crystal plane in the substrate is (1¯10)γ, lathy ferrite will grow parallel.
► Parallel lathy ferrite was elongated in [1¯10]γ during solidification due to low misfit.