Characterization and comparative analysis of the tensile properties of five tempered martensitic steels and an oxide dispersion strengthened ferritic alloy irradiated at ≈295 °C to ≈6.5 dpa

Abstract

Tensile test results at 25 and 300°C on five 9-12Cr tempered martensitic steels and one 14Cr oxide dispersion strengthened alloy, that were side-by side irradiated to 6.5 dpa at 295°C in the Advanced Test Reactor (ATR), are reported. The engineering stress-strain curves are analyzed to provide true stressstrain constitutive ()laws for all of these alloys. In the irradiated condition, the () fall into categories of: strain softening, nearly perfectly plastic and strain hardening. A range of increases in yield stress ( y ) and reductions in uniform strain ductility (e u ) are observed, where the latter can be understood in terms of the alloy's () behavior. Increases in the average () in the range of 0-10% strain are smaller than the corresponding  y , and vary more from alloy to alloy. The data are also analyzed to establish relations between  y and coupled changes in the ultimate stresses as well as the effects of both test temperature and the unirradiated yield stress ( yu ). The latter shows that higher  yu correlates with lower  y . In five out of six cases the effects of irradiation are generally consistent with previous observations on these alloys. However, the particular heat of the 12Cr HT-9 tempered martensitic steel in this study has a much higher e u than observed for earlier heats. The reasons for this improved behavior are not understood and may be microstructural in origin. However, it is noted that the new heat of HT-9, which was procured under modern quality assurance standards, has lower interstitial nitrogen than previous heats. Notably there is a general relation between lower interstitial solute contents and improved ductility, and homogenous deformation, in broadly similar steels.

Tensile deformation and fracture properties of a 14YWT nanostructured ferritic alloy

“…Better understanding of how the mix of texturing, damage and extrinsic factors govern tensile deformation of NFA-1 will be investigated in future studies. These studies will be based on finite element simulations, which we routinely use to extract post-necking true () constitutive laws [9,27] from tensile test s(e) data. The future simulations will treat all of the extrinsic factors noted above.…”

“…The NOs retard dislocation climb and glide, stabilize grain and dislocation structures, and trap helium in fine bubbles that retard swelling and grain boundary embrittlement [1][2][3][4][5][6][7]. Unlike many very high strength materials, NFAs often exhibit significant ductility and reasonable fracture toughness in standard test orientations [8][9][10][11][12].…”

Second Annual Progress Report on Correlation Between Microstructure and Mechanical Properties of Neutron-Irradiated Ferritic-Martensitic and Austenitic Steels

“…The composition of T91 is listed in Table 4. Both TA04 and TA#1c samples were tensile tested at room temperature, with the results reported by Maloy et al [15]. The samples received at ORNL were hole-punched from the tab section of the tensile-tested samples.…”

“…TA04) Also reported 0.002O and 0.021Co. The steel was normalized at 1040°C for 1 h with air cooling and tempered at 760°C for 1 h with air cooling[15].…”

Post-Irradiation-Examination of the ORNL and LANL Samples

“…The composition of T91 is listed in Table 4. Both TA04 and TA#1c samples were tensile tested at room temperature, with the results reported by Maloy et al [14]. The samples received at ORNL were hole-punched from the tab section of the tensile-tested samples.…”