NSUF 17-933: Sample Preparation for Ex-situ Transmission Electron Microscopy Study of Deformation-induced Twinning and Martensite in Two 316L Austenitic Stainless Steels: Role of Stacking Fault Energy and Grain Orientation
A preliminary experiment was conducted at Oak Ridge National Laboratory’s Spallation Neutron Source. It consisted of room temperature neutron diffraction in situ straining of two heats of 316L steels (Fe-10Ni-17Cr-0.003C-0.75Si-3Mo-1Mn and Fe-14Ni-17Cr-0.03C-0.1Si-3Mo-1Mn) designed to have a large stacking fault energy difference. In situ neutron diffraction allowed the observation of deformation behavior per grain orientation. In particular, the evolution of stress levels per grain orientation was estimated. Initial results also include the observation of i) significant differences in the propensity of both steels to form stacking faults during straining, ii) pronounced martensitic transformation for only one of the alloys, iii) differences in dislocation density evolution between the two steels for certain grain orientation, but not for others. The proposed project objective is to fully characterize deformation-induced microstructural features in the two strained 316L alloys for three different grain orientations at two strain levels. In particular it will elucidate i) the origin of differences in stacking fault surface fraction between the two steels (dissociated dislocations or extended stacking faults) ii) the differences in deformation-induced twin fraction between the two steels, iii) the role of grain orientation on martensitic transformation, iv) the differences in dislocation structures between the two steels. All observations will be done for similar grain orientations according to the tensile axis, in order to isolate the effect of composition from the effect of grain orientation. Differences in stress levels for similar orientations will be estimated thanks to the in situ neutron diffraction data. The proposed experiment at MaCS will consist in FIB lift out of several samples for TEM characterization. For both 316L alloys, two pre-strained (0.5% and 10%) specimens will be used. Specimens used for interrupted tensile tests are 0.75 mm thick, which prevents traditional TEM sample preparation through electropolishing to be used. In each specimen, EBSD will be used to select grains with orientation {111}, {110} and {100} according to the tensile axis. The total number of lift-outs will be 2 x 2 x 3 = 12.
Additional Info
| Field | Value |
|---|---|
| Abstract | A preliminary experiment was conducted at Oak Ridge National Laboratory’s Spallation Neutron Source. It consisted of room temperature neutron diffraction in situ straining of two heats of 316L steels (Fe-10Ni-17Cr-0.003C-0.75Si-3Mo-1Mn and Fe-14Ni-17Cr-0.03C-0.1Si-3Mo-1Mn) designed to have a large stacking fault energy difference. In situ neutron diffraction allowed the observation of deformation behavior per grain orientation. In particular, the evolution of stress levels per grain orientation was estimated. Initial results also include the observation of i) significant differences in the propensity of both steels to form stacking faults during straining, ii) pronounced martensitic transformation for only one of the alloys, iii) differences in dislocation density evolution between the two steels for certain grain orientation, but not for others. The proposed project objective is to fully characterize deformation-induced microstructural features in the two strained 316L alloys for three different grain orientations at two strain levels. In particular it will elucidate i) the origin of differences in stacking fault surface fraction between the two steels (dissociated dislocations or extended stacking faults) ii) the differences in deformation-induced twin fraction between the two steels, iii) the role of grain orientation on martensitic transformation, iv) the differences in dislocation structures between the two steels. All observations will be done for similar grain orientations according to the tensile axis, in order to isolate the effect of composition from the effect of grain orientation. Differences in stress levels for similar orientations will be estimated thanks to the in situ neutron diffraction data. The proposed experiment at MaCS will consist in FIB lift out of several samples for TEM characterization. For both 316L alloys, two pre-strained (0.5% and 10%) specimens will be used. Specimens used for interrupted tensile tests are 0.75 mm thick, which prevents traditional TEM sample preparation through electropolishing to be used. In each specimen, EBSD will be used to select grains with orientation {111}, {110} and {100} according to the tensile axis. The total number of lift-outs will be 2 x 2 x 3 = 12. |
| Award Announced Date | 2017-04-26T10:09:52.327 |
| Awarded Institution | Center for Advanced Energy Studies |
| Facility | Microscopy and Characterization Suite |
| Facility Tech Lead | Yaqiao Wu |
| Irradiation Facility | None |
| PI | Gabriel Meric de Bellefon |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 933 |