TEMPERATURE EFFECT ON SERRATED FLOW IN ADDITIVELY MANUFACTURED GH4169 THIN-WALLED PARTS BASED ON DIGITAL IMAGE CORRELATION

Laser powder bed fused (LPBF) GH4169 thin-walled components hold significant promise for hot-section parts in aero-engines; however, the underlying mechanism of their serrated flow (Portevin-Le Chatelier, PLC) behavior at high temperatures remains unclear. In this study, a bi-prism-based single-lens three-dimensional digital image correlation (BSL 3D DIC) technique was employed to systematically investigate the dynamic strain aging (DSA) characteristics of an LPBF-fabricated GH4169 thin-walled structural simulation part (aero-engine combustion chamber casing) over a wide temperature range from 25 °C to 750 °C. The temperature window for the PLC effect under a strain rate of 10⁻³ s⁻¹ has been identified as 250 °C to 650 °C. Within this window, the temperature dependences of serration number, amplitude, period, and plastic strain increment were quantitatively characterized in detail. The obtained results clearly show that the serration number exhibits a unimodal peak at 350 °C, while the average serration amplitude increases monotonically with temperature, revealing a transition from “high-frequency low-amplitude” to “low-frequency high-amplitude”. Under the present test conditions, the plastic strain increment (the difference between the critical strain and the yield strain) reaches its minimum at 450 °C. Full-field strain evolution analysis reveals repeated migration and competition of deformation bands between the upper and lower ends of the specimen at 550 °C. The 25 °C PLC-free comparative test, together with cross-sectional area evolution analysis, demonstrates that the PLC effect, by mediating the spatio-temporal evolution of deformation bands, modulates the spatial distribution of local damage accumulation and thereby correlates with the final fracture location. Concurrently, the serration periods at 250 °C exhibit significant discreteness, while serrations at 650 °C disappear completely in the later stage of deformation. This study systematically reveals the temperature-dependent regulation of serrated flow behavior in LPBF-fabricated GH4169 thin-walled structural simulation parts at a strain rate of 10⁻³ s⁻¹, thus providing solid experimental evidence for the analysis of plastic instability in additively manufactured nickel-based superalloy materials and structures.