NSUF 24-4967: Understanding the Remarkable Strain-Hardening Capacity of Irradiated PM-HIP 316L SS.
The objective of this project is to understand the deformation mechanism, especially the origins of the exceptional strain-hardening capacity and ductility in neutron-irradiated 316L stainless steel (SS) manufactured by powder metallurgy with hot isostatic pressing (PM-HIP) compared to its wrought counterpart. PM-HIP is considered an advanced manufacturing technique with enormous potential owing to the manufactured components’ equiaxed grain structures, improved weldability, enhanced inspectability, near-net shape manufacture, elimination of casting defects, and scalability to heavy nuclear structures. For successful deployment of PM-HIP components in the nuclear industry, their mechanical and microstructural evolution under irradiation must be understood completely to benchmark these as comparable or superior to their conventionally manufactured counterparts. In a recent study, neutron-irradiated PM-HIP 316L SS exhibits superior mechanical properties – lower irradiation hardening (compared to its unirradiated condition), exceptional strain hardening coefficient, higher uniform tensile strength, and greater ductility – compared to wrought 316L SS, even though the irradiated microstructures of wrought and PM-HIP 316L (before tensile deformation) contain statistically identical dislocation loops, voids, and black dots. These phenomena indicate that the conventional Orowan strengthening mechanism is not likely applicable to PM-HIP 316L, as it would lead to incorrect prediction of identical irradiation hardening between the wrought and PM-HIP alloys. Instead, it can be hypothesized that the greater strain-hardening capacity and higher ductility in the PM-HIP 316L than in the wrought 316L might be attributed to a greater propensity for the PM-HIP material to undergo deformation induced phase transformations and deformation twinning, possibly due to the finer-grained microstructure in PM-HIP 316L than that of wrought 316L. To understand this deformation mechanism, a multiscale characterization approach, containing scanning electron microscopy with electron backscatter diffraction (SEM-EBSD) for µm-scale identification of deformation twins and transformations, coupled with complementary high-resolution scanning/transmission electron microscopy (HR-S/TEM) for targeted nm-scale confirmation of the relationship between irradiation-induced defects and deformation twins and phase transformations, will be used to correlate microstructure and deformation mechanisms along the cross-section of the broken tensile bars. Neutron irradiated tensile bars of PM-HIP and wrought 316L available in the NSUF library (through our previous program 15-8242), as well as unirradiated control specimens, will be selected for these microstructural studies. Thus, to engineer exceptional mechanical resilience in steels (and beyond) under irradiation, there is a critical need to understand how the deformation mechanisms of PM-HIP and wrought 316L differ.
추가 정보
| 필드 | 값 |
|---|---|
| Award Announced Date | 2024-05-28T17:10:06.03 |
| Awarded Institution | Purdue University |
| Facility Tech Lead | Alina Montrose, Yaqiao Wu |
| Irradiation Facility | |
| PI | Arya Chatterjee |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | None |