双相不锈钢各组相循环变形行为的纳米压痕试验和有限元表征方法研究

对双相不锈钢的奥氏体相和铁素体相,分别开展了不同加载模式(接触载荷和压入位移)和不同加载波形下的单向、循环纳米压痕试验,对比分析了两相的基本力学性能和压痕循环变形行为的演化规律。基于压痕试验结果和修正ABDEL-KARIM-OHNO非线性随动硬化准则的弹塑性本构模型,提出一套双相不锈钢奥氏体相和铁素体相的塑性和循环塑性行为的本构模型参数表征方法。通过对微结构代表性体积单元整体拉伸和循环变形行为进行模拟,并与宏观试验结果对比,验证了参数表征方法的合理性。研究结果表明,铁素体相的强度、硬度和抗棘轮变形的能力均高于奥氏体相,两相之间通过晶界产生一定的交互作用;在接触载荷控制的循环加载条件下,奥氏体相与铁素体相均产生明显的压痕棘轮现象,且载荷水平越高压痕棘轮变形程度越大;所发展的本构模型参数表征方法可为研究多相材料各组相、小体积材料的循环变形行为提供借鉴和参考。

Nanoindentation Experiment and Finite Element Characterization of the Cyclic Deformation Behavior of Duplex Stainless Steel

The basic mechanical properties and the cyclic indentation deformation behavior of the austenitic and ferrite phases of duplex stainless steel are discussed and compared through the monotonic and cyclic nanoindentation experiments with different loading modes (indentation load and displacement controlled) and different loading waveforms. Based on the indentation experiment results and the elastoplastic constitutive model combined with modified ABDEL-KARIM-OHNO nonlinear dynamic hardening rule, a constitutive model parameter characterization method for the plastic and cyclic plastic behavior of austenite and ferrite phases in duplex stainless steel is developed. The rationality of the parameter characterization method is verified by simulating the overall tensile and cyclic deformation behavior of the representative volume unit of duplex stainless steel, and comparing with the macroscopic experimental results. It is shown that the strength and hardness of the ferrite phase are higher than those of the austenite phase, and the two phases have a certain interaction through the grain boundary. Both the austenite phase and the ferrite phase exhibit obvious indentation ratcheting phenomenon under cyclic indentation loadings, while the ratcheting deformation increases with loading levels. The developed constitutive model parameter characterization method can provide reference for studying the cyclic deformation behavior of each phase of multiphase materials and small-volume materials.