1. 1 Sandia Fracture Challenge Microstructure Characterization Yuxiong Mao, PhD Mark Horstemeyer, CAVS Chair Professor Center for Advanced Vehicular Systems Mississippi State University

2. 2 15-5PH Stainless Steel Plate Six samples were made from the received specimen to observe the Longitudinal- Transverse (LT1&LT2), Longitudinal-Thickness (LS1&LS2), Transverse-Thickness (TS1&TS2) sections. Samples were mounted and polished. Then etched with Vilella's reagent for 90 seconds.

3. 3 LT1 & LT2 Before Etch LT1 Overview LT2 Overview LT sections are homogeneous. Very few inclusions can be found in these sections. Note the lines here are polish scratches. Inclusions

4. 4 LT1 Before Etch High Resolution View

5. 5 LS1 Before Etch Near Surface Center High Resolution View Overview Inclusions Banding and inclusions can be observed in LS sections. The inclusions are aligned along the longitudinal direction. The bands run through the entire sample and are clustered in the center region.

6. 6 LS2 Before Etch Near Surface Center High Resolution View Overview

7. 7 TS1 Before Etch Near Surface Center High Resolution View Overview Banding and inclusions can also be observed in TS sections. The bands are shorter compared to those in LS sections.

8. 8 TS2 Before Etch Near Surface Center High Resolution View Overview

9. 9 Quantitative Analyses of the inclusions observed in LS and TS un-etched sections Area Fraction(%)Number Density(/um^2)Average Area (um^2) Average NND(um) LS10.10144.261E-042.37918.578 LS20.08253.164E-042.60820.318 TS10.15347.093E-042.16216.138 TS20.16498.394E-041.96514.474

10. 10 LT1 After Etch: Martensite Dominated OverviewHigh Resolution View Homogenous Martensitic matrix covers the entire LT sections. Martensitic matrix

11. 11 LT2 After Etch OverviewHigh Resolution View

12. 12 LS1 After Etch: Ferrite Banding is an Issue Overview Banding Near Surface Center High Resolution View Ferrite Stringer Banding/segregations can be observed in LS sections. The bands run through the entire sample and are clustered in the center region. The bands are aligned along the longitudinal direction. These segregations may have detrimental effects on the mechanical properties (a). (a) B. Potter, “NDT of Precipitation Hardened Steels Using Fluorescent Magnetic Particle Testing,” NDT Solution, December 2003

13. 13 LS2 After Etch Overview Near Surface Center High Resolution View

14. 14 TS1 After Etch Overview Near Surface Center High Resolution View Banding/segregations can also be observed in TS sections. The bands are aligned along the transverse direction and are shorter than those in LT sections. Banding

15. 15 TS2 After Etch Overview Near Surface Center High Resolution View

16. 16 Grain Boundary Segmentation

17. 17 Grain Size Distributions: Change Hardening Behavior Locally SampleLT1LT2LS1LS2TS1TS2 Average Grain Size (um) 4.544.804.014.303.713.56