A D V A N C E D M A T E R I A L S & P R O C E S S E S | A P R I L 2 0 2 2 2 3 conditions are presented alongside a scanning electron micrograph of a residual PIP indent applied to a WAAM-processed maraging 250 steel system. PIP testing and analysis found the yield strength, ultimate tensile strength, and characteristic strain for both the as-printed and heat treated conditions to be 950 and 838 MPa, 1333 and 1022 MPa, and 13% and 50%, respectively. Testing was conducted parallel to the build direction and equidistant from the deposit-substrate interface and specimen surface. Soon, the degree of information obtained via PIP testing and analysis of the WAAM-processed steels discussed here will be enhanced. PIP line scans are currently being measured for region-specific property insights; multiple orientations relative to the build, traverse, and step directions are being characterized; substrate-free WAAM-processed and thermally post- processed specimens are being characterized to explore the relationship between residual stress states and resultant PIP behavior. CONSTRAINTS AND LIMITATIONS Like all materials characterization methods, PIP has its limitations. For example, PIP testing should not be performed within 3 mm of a specimen’s given edge. In addition, one must avoid near-edge measurements to ensure that the presence of both free edges and the edge of the specimen in contact with the mounting matrix material will not influence the plastic deformation field formed during testing. This could reduce PIP test accuracy due to the potential for deviations from radial symmetry, which would violate the underlying principles within the indentation models. For high-fidelity PIP testing and analysis, one must also consider specimen curvature and surface roughness variation boundaries. Currently, the maximal radius of curvature is 1 m, and themaximal surface roughness is 10μm; however, surface roughness of 3 μm or less, or surfaces that have been polished using P1200-P2400 grit polishing paper, is ideal for PIP applications. To date, materials that can be tested via PIP include pure and alloyed aluminum, steel, titanium, nickel, copper, and cobalt systems. Note that materials with yield strengths well above 2000-3000 MPa are also currently out of range. RECENT PROGRESS PIP testing and analysis are steadily gaining wider adoption and further integration within various sectors of the metallurgical andmaterials engineering Fig. 4 — PIP analysis of as-printed and stress-relieved WAAM-processed maraging 250 steel systems.
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