3-24. Multiscale models for creep rupture of austenitic stainless steels

Abstract: Austenitic stainless steels are candidate materials for the critical components serving at high temperatures and stresses for a long time, where creep damage is life controlling. Empirical models are frequently used for the creep rupture; However, they have the shortcomings that the fitting parameters do not have any physical meanings, and it is not reliable for a long-term extrapolation. Thus, the multiscale fundamental models have been proposed, where brittle and ductile creep rupture are considered, all parameters are well defined. Brittle creep rupture results from formation, growth and coalescence of creep cavities on sliding grain boundaries. Ductile creep rupture is based on dislocation mechanism, including dislocation hardening, precipitation hardening, solid solution hardening and stacking faults. By coupling the brittle and ductile creep rupture models, the creep rupture strength of austenitic stainless steels can be predicted quantitatively, as shown in Figure 1. The main parameters in the fundamental models are calculated with the thermodynamic software MatCalc and the first-principles methods. Multiscale fundamental models include: physical parameters calculated from the first-principles methods; theoretical models based on the evolution of microstructure and defects; prediction of the macro-mechanical behavior.
Keywords: creep models; creep damage mechanics; multiscale models; first-principles calculations; austenitic stainless steels

Figure 1. Creep rupture life prediction of TP321H (18Cr12NiTi) austenitic stainless steels based on multiscale fundamental models at temperatures of 600 and 700 °C
图 1. 基于多尺度基本模型预测 TP321H(18Cr12NiTi)奥氏体不锈钢在 600 和 700 °C下的蠕变寿命

     基于多尺度模型预测奥氏体不锈钢的蠕变寿命

贺君敬*1，Sandström Rolf 2，张 晶 2，Pavel Korzhavyi 2

 1.杭州电子科技大学;2.皇家理工学院 

摘要:奥氏体不锈钢因其优异的高温性能而被广泛应用于火力发电、核电等领域。在长期高温高压服役条件下，蠕变损伤成为影响材料寿命的重要因素。经验模型经常被用来表征蠕变断裂，但经验模型中的拟合参数不具有任何物理意义;且在外推材料长期蠕变寿命时，其可靠性会下 降。为此，本研究提出了能够表征蠕变断裂机制的多尺度基本模型，模型中所涉及参数均有明 确定义。蠕变断裂包括脆性蠕变断裂和韧性蠕变断裂。脆性蠕变断裂是由于晶界滑移导致蠕变 孔洞的形成、长大和连接;韧性蠕变断裂主要是基于位错蠕变机制，分别考虑了位错强化、析 出强化、固溶强化和堆垛层错等的影响。通过耦合韧性蠕变断裂模型和脆性蠕变断裂模型，可 以定量的预测奥氏体不锈钢的蠕变寿命，如图 1 所示。基本模型中的主要参数如析出相等主要 通过热动力学软件 MatCalc 等计算;堆垛层错能、弹性常数及晶格错配参数等，主要通过第一 性原理计算获得。多尺度基本模型的本质是:在原子尺度，通过第一性原理计算基本模型的物 理参数;在微观尺度，基于微观组织结构和缺陷的演化建立基本的理论模型;进而预测材料的 宏观力学性能如蠕变寿命等。

关键词:蠕变模型;蠕变损伤机制;多尺度模型;第一性原理计算;奥氏体不锈钢