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 1 parameters. In contrast, PIP testing can more easily identify optimal process- ing parameters in a high-throughput manner. As such, heat treatment optimization and tuning for application-specific performance requirements arewell suited for PIP testing and analysis integration. This is especially relevant for the aluminum, steel, nickel, titanium, cobalt, and copper-centric domains of expertise. Accordingly, the Cote Research Laboratory at Worcester Polytechnic Institute (WPI) is actively working with Solvus Global, also located in Worcester, Mass., the U.S. Army Research Laboratory, the University of Massachusetts Amherst, the Metals Processing Institute, Florida International University, Mississippi State University, and others to utilize PIP in this way further. For example, the thermal post-processing optimization of wire arc additive manufacturing (WAAM)-based maraging 250 steel systems is underway. Beyond heat treatment optimization, advanced processing parameters are being evaluated for cold spray additive manufacturing (CSAM), WAAM, photopolymer additive manufacturing (PAM), directed energy deposition (DED), and additional materials processing methods. CASE STUDY 1: COMPARISON OF PROCESSING TECHNIQUES To demonstrate the utility of PIP testing within the realm of processing method selection, Al 6xxx specimens were produced via high-pressure nitrogen CSAM, a hybrid combination of shot peening and high-pressure nitrogen CSAM, arc melting, and extrusion. The CSAM-based Al 6xxx consolidations were processed using a 0071 polybenzimidazole nozzle, a cold spray system from VRC Metal Systems, Box Elder, S.D., an inertly gas-atomized Al 6061 feedstock powder, and a wrought Al 6061-T651 build plate. The arc melted specimen was produced using wrought Al 6061-T651 and an electric arc as a thermal energy source. As for the hybrid combination of shot peening and high-pressure nitrogen CSAM consolidations, the same pro- cessing parameters, feedstock, hard- ware, and system were used; however, shot peening was introduced at constant intervals of deposited layers. Further, while a roughness of ap- proximately 3 μm or less is best for PIP testing, specimens were compression mounted using phenolic mounting material and a SimpliMet 4000 system from Buehler, Lake Bluff, Ill. This was followed by grinding and polishing for metallographic preparation using a Buehler EcoMet 300 automatic polisher until a mirror finish was achieved using a 0.02 μm colloidal silica suspension. After that, PIP testing was performed per prescribed protocols, execution of the tests via CORSICA 2.0, and analysis via SEMPID (software for extracting material properties from indentation data). Figure 2 shows testing results and analysis. In addition to the nominal or engineering stress-strain curves obtained andpresented for the arcmelted, hybrid CSAM and shot-peened, high-pressure CSAM deposited, and extruded Al 6xxx specimens, onecan identifythat theprocessing technique achieves the desired Fig. 2 — Nominal and true stress-strain curves for the four uniquely processed Al 6xxx series studied here.
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