In additive manufacturing (AM), numerous thermal cycles make stress relaxation a significant factor in affecting the material mechanical response. However, the traditional material constitutive model cannot describe repeated annealing behavior. Here, we propose an improved constitutive model based on a serial of stress relaxation experiments, which can descript the temperature and time-dependent stress relaxation behavior during AM. By using the proposed relaxation model, the prediction accuracy is significantly improved due to the recovery of inelastic strain during multilayer deposition. The results are validated by both in-situ and final distortion measurements. The influence mechanism of the relaxation behavior on material mechanical response is explained by the three-bar model in thermo-elastic-plastic theory. The relaxation behavior during the whole AM process is clarified. The stress behavior is found to have a limited effect when merely depositing several layers; nevertheless, it becomes a prominent impact when depositing multiple layers. The proposed model can enhance modeling accuracy both in AM and in multilayer welding.

在增材制造（AM）中，大量的热循环使应力松弛成为影响材料机械响应的重要因素。但是，传统的材料本构模型无法描述重复的退火行为。在此，我们基于一系列应力松弛实验提出了一种改进的本构模型，该模型可以描述AM中温度和时间相关的应力松弛行为。通过使用所提出的松弛模型，由于多层沉积过程中非弹性应变的恢复，预测精度得到了显着提高。结果通过现场和最终失真测量得到验证。用热弹塑性理论中的三杆模型解释了松弛行为对材料力学响应的影响机理。阐明了整个增材制造过程中的松弛行为。当仅沉积几层时，发现应力行为的作用有限。然而，当沉积多层时，它成为显着的影响。所提出的模型可以提高AM和多层焊接中的建模精度。