## 2 Materials and Methods
### Small punch Test (SPT) Protocols  
[PERSON] and [PERSON] [27] performed a review of the historical applications of SPT for mechanical evaluation of materials and indicated that comparing experimental SPT results with FE computations is necessary to gather relevant material properties. Earlydevelopment of SPT was performed to satisfy niche applications in the nuclear industry. [PERSON] et al. [28] suggested that a low cost and quick test was necessary to assess mechanical behavior in a variety of alloys used in nuclear reactors. [PERSON] et al. [29] further elaborated on the application of SPT in the nuclear industry by arguing that SPT can be used to study mechanical degradation in neutron-irradiated materials using exceedingly small material volumes. [PERSON] et al. [30] used a test method where a thin plate (\(\sim\)0.5 mm thickness) was firmly clamped between two dies with a circular opening centered over the plate in both the upper and lower dies (see Figure 4a). The method they used was found to produce consistent load-displacement results and was employed for this research study. The load-displacement results from each SPT sample were utilized in this research study to obtain a true stress-true plastic strain response from which UTS and yield strength were determined. Standards are currently being developed for SPT. CWA-15627 [31] was an initial attempt at standardization of SPT which took place at the CEN Workshop Agreement-CWA in Europe. [PERSON] et al. [32] more recently attempted to document and standardize SPT by summarizing the current practice of SPT and the details for a future standard. SPT samples were prepared for testing by directly polishing both sides of the samples against an 800-grit followed by a 1000-grit sandpaper until the removal of the as-WEDM recast layer is visually indicated. After polishing, each SPT sample was measured for thickness in three locations using a micrometer and variance within each sample was maintained below 15 um. An average of the thickness measurements was recorded and used in the simulations and analysis necessary to extract intrinsic mechanical properties from SPT experimental results. SPT was carried out using the same indention machine that performed MSS. This process involved placing an SPT sample over a 4 mm hole in a lower fixture and clamping the sample with an upper fixture as shown in Figure 4a. A lubricant was applied to the surface of the SPT sample to reduce friction during the contact with the punch. [PERSON] et al. [30] demonstrated successful SPT repeatability by using a 2.4 mm punch tip and a 4 mm fixture hole, so those dimensions were used in the  
Figure 4: (**a**) A schematic of the SPT experimental setup. (**b**) A typical measured SPT load-displacement curve. (**c**) Finite element (FE) mesh used for SPT simulations. application of this work. The assembled fixture containing the clamped sample was then placed on the indenter stage. The optical microscope on the indenter machine was used to adjust the placement of the sample fixture so that the indenter was at the center of the unsupported span of the sample (see the schematic in Figure 4a). [PERSON] et al. [33] used a punch displacement rate of 0.5 mm/min and successfully demonstrated the accuracy of test results using this rate on a variety of different materials. As such, this study used an identical loading rate during SPT analysis. The test was terminated when the punch force exhibited a clear peak, as shown in the circle in Figure 4b, which indicated that the sample has been punched through. A few different corrections to the measured load-displacement curves were necessary before applying SPT analyses protocols described in Section 3.2. A zero-point correction in the form of the subtraction of a constant value was needed for the measured displacement. This constant value is established by fitting the very early elastic portion of the SPT load-displacement curve to a linear model and examining where it intersects the x-axis of the plot.