Constitutive modeling and failure mechanisms of anisotropic tensile and creep behaviors of nickel-base directionally solidified superalloy
Constitutive modeling and failure mechanisms of anisotropic tensile and creep behaviors of nickel-base directionally solidified superalloy
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DOI：
10.1016/j.matdes.2012.09.031
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发表时间：
2013-03
影响因子：
8.4
通讯作者：
D. Shi;Cheng-Li Dong;Xiaoguang Yang
中科院分区：
文献类型：
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作者：
D. Shi;Cheng-Li Dong;Xiaoguang Yang
建立了一个横向各向同性连续弹粘塑性模型，以描述定向凝固镍基高温合金的拉伸和蠕变行为。引入四阶张量来模拟材料的各向异性。将Kachanov损伤演化方程与应力张量相结合，提高了蠕变的建模能力。该模型使用自适应显式集成方案作为ABAQUS用户材料（UMAT）子程序实现。通过拟合等温拉伸和高温蠕变载荷试验曲线，采用分组优化策略确定材料参数。利用扫描电子显微镜（SEM）和能量色散x射线光谱仪（EDXS）观察断裂形貌，探讨了断裂机理。结果表明，考虑各向异性和蠕变损伤的Chaboche本构模型能够较好地表征DS高温合金速率相关的各向异性拉伸和蠕变行为，仿真结果与实验数据吻合较好。DS高温合金的拉伸断口主要由大解理面和少量韧窝组成。同时，DS高温合金在760℃和850℃时的蠕变断裂机制为韧窝积累引起的穿晶断裂。760°C时的韧窝和非金属夹杂物的形貌与850°C时不同。
A transversely isotropic continuum elasto-viscoplasticity model is formulated to capture the tensile and creep behaviors of a directionally solidified (DS) nickel-base superalloy. A fourth-order tensor is introduced to model material anisotropy. The Kachanov damage evolution equation is coupled with stress tensor to improve capability of modeling creep deformation. This model is implemented as an ABAQUS user material (UMAT) subroutine using a self-adaptive explicit integration scheme. A grouping optimization strategy is employed to identify the material parameters by fitting experimental curves of isothermal tension and creep loading at high temperature. Failure mechanisms are investigated by observing the fracture morphology by means of Scanning Electron Microscope (SEM) with the Energy Dispersive X-ray Spectrometer (EDXS). The results obtained showed that Chaboche constitutive model coupled with anisotropy and creep damage was able to characterize the rate-dependent anisotropic tensile and creep behaviors of DS superalloy and the simulation results agreed well with the experimental data. The tensile fracture surface of DS superalloy mainly contained a mixture of large cleavage planes and small amount of dimples. Meanwhile, the creep fracture mechanism of DS superalloy at 760 and 850°C was transgranular fracture induced by the dimple accumulation. The morphology of the dimples and non-metallic inclusions at 760°C was different from that at 850°C.