标题： 温度和取向差依赖的中锰钢铁素体晶界奥氏体形核：取向差依赖的晶界偏析的作用 显示英文标题

标题： Temperature and misorientation-dependent austenite nucleation at ferrite grain boundaries in a medium manganese steel: role of misorientation-dependent grain boundary segregation

摘要： 在当前的工作中，我们研究了晶界（GB）取向偏差依赖的偏析在50%冷轧临界退火的10Mn-0.05C-1.5Al（wt。%）中锰钢中奥氏体形核中的作用。 在500{\deg }C的临界退火过程中，奥氏体主要在高角度晶界处形核。 在600{\deg }C时，奥氏体 additionally 在低角度晶界处形核，表现出温度依赖性。 相关透射Kikuchi衍射/原子探针断层扫描显示了取向依赖的偏析。 虽然已报道晶界偏析有助于中锰钢（3-12 wt.% Mn）的奥氏体形核，但对温度和取向依赖性的理解仍然缺乏，这是当前工作的目标。 由于原子探针的伪影可能导致偏析宽度的扩展，我们将实验与密度泛函理论（DFT）计算结果相结合，结果表明Mn的偏析不仅限于晶界平面，而是局限于大约1 nm的区域。 因此，晶界偏析改变了晶界界面能以及对应于转变的单位体积自由能。 我们估计了考虑约1 nm偏析宽度的奥氏体形核的局部驱动力。 基于经典形核理论，我们阐明了晶界偏析对在晶界处受限奥氏体形核的临界半径和活化能垒的影响。 显示英文摘要

摘要： In the current work, we study the role of grain boundary (GB) misorientation-dependent segregation on austenite nucleation in a 50% cold rolled intercritically annealed 10Mn-0.05C-1.5Al (wt. %) medium Mn steel. During intercritical annealing at 500{\deg}C, austenite nucleates predominantly at high-angle GBs. At 600{\deg}C, austenite nucleates additionally at low-angle GBs, exhibiting a temperature dependance. Correlative transmission Kikuchi diffraction /atom probe tomography reveals a misorientation-dependent segregation. While GB segregation has been reported to assist austenite nucleation in medium manganese steels (3-12 wt.% Mn), an understanding of the temperature and misorientation dependance is lacking, which is the aim of current work. Since artifacts of atom probe can cause a broadening of the segregation width, we combined experiments with results from density functional theory (DFT) calculations that reveal that the Mn segregation is not limited to the GB plane but confined to a region in the range of approximately 1 nm. Consequently, GB segregation alters both the GB interface energy and the free energy per unit volume corresponding to the transformation. We estimate the local driving force for austenite nucleation accounting for the segregation width of ~ 1 nm. Based on classical nucleation theory, we clarify the effect of GB segregation on the critical radius and activation energy barrier for confined austenite nucleation at the GB.