Abstract Microstructures of both as-quenched and intercritical-annealed medium-Mn steel were investigated by transmission electron microscopy to acquire a better understanding of γ–ɛ and γ–α′ martensitic transformations. The orientation relationships among each phases were determined as ( 1 ¯ 10 ) α ′ / / ( 0001 ) e , [ 111 ] α ′ / / [ 11 2 ¯ 0 ] e for the case of as-quenched sample, and ( 1 ¯ 10 ) α ′ / / ( 1 ¯ 11 ) γ / / ( 0001 ) e , [ 111 ] α ′ / / [ 110 ] γ / / [ 11 2 ¯ 0 ] e for the case of intercritical-annealed sample, respectively. In addition, the presences of core-shell type microstructures with the gradient of Mn concentration were confirmed with ɛ–martensite being surrounded by retained γ. Mn concentration of each phase was found dependent on the growth of reversed γ controlled by Mn diffusion during intercritical annealing. It was strongly suggested that the gradient of Mn concentration occurred during intercritical annealing affected the phase stability, which resulted in the formation of e/γ core-shell microstructures.

中文翻译：

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双相马氏体钢核壳型组织的形成

摘要 通过透射电子显微镜研究淬火态和临界间退火中锰钢的显微组织，以更好地了解 γ-ɛ 和 γ-α' 马氏体转变。各相间的取向关系确定为 ( 1 ¯ 10 ) α ′ / / ( 0001 ) e , [ 111 ] α ′ // [ 11 2 ¯ 0 ] e 对于淬火样品, 和 ( 1 ¯ 10 ) α ′ // ( 1¯ 11 ) γ // ( 0001 ) e , [ 111 ] α ′ // [ 110 ] γ // [ 11 2 ¯ 0 ] e 分别为临界区退火样品。此外，随着 ɛ-马氏体被保留 γ 包围，证实了具有 Mn 浓度梯度的核壳型微观结构的存在。发现每个相的 Mn 浓度取决于在临界间退火期间由 Mn 扩散控制的反向 γ 的生长。