316L奥氏体不锈钢高温单拉和蠕变行为的实验和晶体塑性模拟研究

Tensile and creep behavior of 316L austenite stainless steel at elevated temperatures:experiment and crystal plasticity modeling

316L奥氏体不锈钢(ASS)因其优异的抗蠕变性和耐腐蚀性被广泛应用于核反应堆中的包壳材料.但由于核反应堆长期处于高温环境,其包壳材料会不断累积蠕变损伤并最终导致性能退化,进而影响设备的安全运行.因此,为保障核反应堆的安全服役,针对其包壳材料高温蠕变行为的研究具有重要意义.基于此,我们开展了316L ASS在高温下的单轴拉伸变形和蠕变行为的研究.结果表明,316L ASS的力学响应具有明显的温度依赖性,且在特定的温度范围(723 K-923 K)和应变率(1.3×10−3 s−1)条件下,显示出明显的动态应变时效效应;此外,316L ASS在高温条件下的主要蠕变机制为位错攀移机制,它一方面会影响位错密度的演化,另一方面会影响位错越过障碍物的激活频率.基于316L ASS在高温下的微结构演化机理,我们建立了基于位错机制的晶体塑性本构模型.在该模型中额外考虑了位错攀移机制对刃型位错湮灭、位错偶极子形成和刃型位错越过障碍物的贡献.最终结果表明,该模型能有效地模拟和预测316L ASS在高温条件下的单轴拉伸和蠕变响应,而该研究成果也为316L ASS的蠕变性能评估提供了重要的理论依据.

In a high-temperature environment,creep rupture is the major failure mode of metallic materials.316L austenite stainless steel has been widely used in nuclear reactors for its extraordinary creep strength and corrosion resistance.In this work,the uniaxial tensile deformation and creep behavior of 316L austenite stainless steel at elevated temperatures are investigated.Firstly,the result shows that 316L austenite stainless steel has an obvious temperature-dependent dynamic strain aging at a specific temperature range(723 K–923 K)with a strain rate of 1.3×10−3 s−1.Furthermore,at elevated temperatures,dislocation climb is the main creep mechanism of 316L austenite stainless steel and can affect dislocation mobility.Then,a dislocation-based crystal plasticity model is established to describe the relationship between the macroscopic mechanical responses and the underlying microscopic dislocation behaviors.Especially,the dislocation climb leads to the annihilation of monopolar dislocations and the formation of dislocation dipoles and helps monopolar dislocations surmount obstacles.Finally,the developed constitutive model is verified to simulate the uniaxial tensile and creep responses of 316L austenite stainless steel at elevated temperatures.The established model is expected to provide a theoretical basis for evaluating the high-temperature creep properties of metallic materials.