Stacking fault energies (SFE) were determined in additively manufactured (AM) stainless steel (SS 316 L) and equiatomic CrCoNi medium-entropy alloys. AM specimens were fabricated via directed energy deposition and tensile loaded at room temperature. In situ neutron diffraction was performed to obtain a number of faulting-embedded diffraction peaks simultaneously from a set of (hkl) grains during deformation. The peak profiles diffracted from imperfect crystal structures were analyzed to correlate stacking fault probabilities and mean-square lattice strains to the SFE. The result shows that averaged SFEs are 32.8 mJ/m2 for the AM SS 316 L and 15.1 mJ/m2 for the AM CrCoNi alloys. Meanwhile, during deformation, the SFE varies from 46 to 21 mJ/m2 (AM SS 316 L) and 24 to 11 mJ/m2 (AM CrCoNi) from initial to stabilized stages, respectively. The transient SFEs are attributed to the deformation activity changes from dislocation slip to twinning as straining. The twinning deformation substructure and atomic stacking faults were confirmed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The significant variance of the SFE suggests the critical twinning stress as 830 ± 25 MPa for the AM SS 316 L and 790 ± 40 MPa for AM CrCoNi, respectively.

译文

在增材制造 (AM) 不锈钢 (SS 316  L) 和等原子CrCoNi中熵合金中确定了堆垛层错能 (SFE)。AM样品是通过定向能量沉积和在室温下拉伸加载制成的。进行了原位中子衍射,以在变形过程中一组 (hkl) 晶粒同时获得许多断层嵌入的衍射峰。分析了从不完全晶体结构衍射的峰轮廓,以将堆积断层概率和均方晶格应变与SFE相关联。结果表明,AM SS 316  L的平均sfe为32.8 mJ/m2,AM CrCoNi合金的平均sfe为15.1 mJ/m2。同时,在变形过程中,从初始阶段到稳定阶段,SFE分别从46至21 mJ/m2 (AM SS 316  L) 和24至11 mJ/m2 (AM CrCoNi) 变化。瞬态sfe归因于变形活动从位错滑移到应变孪晶的变化。通过电子背散射衍射 (EBSD) 和透射电子显微镜 (TEM) 证实了孪晶变形亚结构和原子堆垛层错。SFE的显着方差表明,AM SS 316  L的临界孪生应力分别为830   ±   25  MPa,AM CrCoNi的临界孪生应力分别为790   ±   40 mpa mpa。

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