Interface segregation affects the microstructure evolution and mechanical properties of alloys, including strength, ductility and damage tolerance. This is particularly true for multiphase high-strength steels containing multiple types of interfaces whose characteristics are key factors influencing the steels’ mechanical performance. The different tendencies of solute segregation to different types of interfaces can lead to complex segregation behavior, which needs to be understood. Here, we focus on the segregation behavior of B in a high-Mn, high-Al lightweight steel with a two-phase austenite-ferrite microstructure. We find distinct B segregation at both austenite and ferrite grain boundaries as well as at austenite-ferrite phase boundaries after high temperature annealing (1100°C) and fast quenching. The segregation process is governed by local equilibrium between bulk and interfaces as discussed in terms of thermodynamic and ab initio calculations. Our findings reveal a dependence of B segregation on the interface structure regardless of the adjacent phases, which can be explained in terms of respective interfacial energy in accord with the Gibbs adsorption isotherm. In addition, co-segregation of B and C is observed at both high-angle and low-angle ferrite grain boundaries due to the attractive interaction between the two solutes in the bulk ferrite phase. In contrast, for austenite grain boundaries, C depletion is observed owing to its site competition effect and repulsive interaction with B in austenite. These observations help to guide interface segregation engineering in complex multiphase lightweight steels to improve their mechanical performance.

中文翻译：

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高 Mn 和高 Al 多相轻钢中的界面硼偏析


界面偏析会影响合金的微观结构演变和机械性能，包括强度、延展性和损伤容限。对于包含多种界面类型的多相高强度钢尤其如此，这些界面的特性是影响钢材机械性能的关键因素。溶质对不同类型界面的不同分离趋势会导致复杂的分离行为，这需要了解。在这里，我们关注 B 在具有两相奥氏体-铁素体微观结构的高 Mn、高 Al 轻钢中的偏析行为。在高温退火 （1100°C） 和快速淬火后，我们在奥氏体和铁素体晶界以及奥氏体-铁素体相界处发现了明显的 B 偏析。分离过程受本体和界面之间的局部平衡控制，如热力学和从头计算所述。我们的研究结果揭示了 B 偏析对界面结构的依赖性，而与相邻相无关，这可以用各自的界面能来解释，这与吉布斯吸附等温线一致。此外，由于体铁氧体相中两种溶质之间的吸引力相互作用，在高角度和低角度铁氧体晶界处都观察到 B 和 C 的共偏析。相比之下，对于奥氏体晶界，由于其位点竞争效应和与奥氏体中 B 的排斥相互作用，观察到 C 耗尽。这些观察结果有助于指导复杂多相轻钢的界面偏析工程，以提高其机械性能。