A Study on Microstructure Evolution, High Temperature Deformation, and Fracture Characteristics of Wire Arc Additively Manufactured Inconel 625 Alloy

Abstract

Abstract. The present research focuses on the hot deformation behavior, microstructure, texture evolution, and fracture mechanisms of wire arc additively manufactured Inconel 625 alloy. The deposited material exhibits columnar, cellular, and dendritic grain structures, with grain widths ranging between 10 μm and 40 μm and lengths extending up to 150 μm. The deformation characteristics were studied across a temperature range of 700–900 °C. At medium temperatures, distinct serrations were observed, transitioning from B type to C type as the temperature increased. At elevated temperatures, B-type serrations reappeared, attributed to interactions between C14-Ni2Nb Laves phases and mobile dislocations, as revealed by transmission electron microscopy (TEM) analysis. Conversely, C-type serrations were associated with the nucleation and growth of deformation twins. Grain size and boundaries under varying deformation temperatures were examined using electron backscattered diffraction (EBSD) and TEM, which revealed the occurrence of dynamic recrystallization (DRX). It was observed that the preferred orientation for DRX nucleation in the Inconel 625 alloy is along the ⟨001⟩ direction. At 900 °C, recrystallized grains were prominent, with EBSD results confirming both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX), where CDRX acted as a secondary nucleation mechanism. Below 900 °C, cracks primarily nucleate due to stress concentrations near Nb-rich phases. At 900 °C, crack initiation was influenced by slip band impingement at grain boundaries combined with stress concentrations around Nb-rich phases. Furthermore, void formation at grain boundary triple junctions caused by grain boundary sliding contributed to ductile fracture. The high-temperature deformation behavior of wire arc additive manufacturing-deposited Inconel 625 is strongly influenced by the interplay of DDRX and CDRX mechanisms.