Crystallography and morphology of a lathy ferrite in Fe-Cr-Ni alloys during directional solidification

摘要

The relationship between morphology and crystallography of an entangled lathy ferrite during directional solidification in Fe-Cr-Ni alloy has been investigated. During solidification, morphology of the lathy ferrite depends on the orientation relationship between the lathy ferrite and austenite. When the plane in the austenite substrate is (111)_γ , "Y-shaped" lathy ferrite grows in an entangled cluster and the orientation relationship between the lathy ferrite and austenite is the Nishiyama-Wassermann relationship. Lathy ferrite is preferentially elongated along 〈211〉_γ and 〈011〉_γ directions on (111)_γ plane due to lower misfit. The included angle among the "Y-shaped" lathy ferrite is about 120° because the angle between each pair of [211]_γ , [112]_γ, and [121]_γ crystal directions is equal to 120°. Formation mechanism of the perpendicular lathy ferrite has also been analyzed according to the relationship between 〈211〉_γ and 〈011〉_γ on (lll)_γ plane. This indicates that required crystal morphology of the lathy ferrite in the solidified microstructure can be obtained by controlling the crystal plane of austenite.