Ductility dip cracking mechanisms and characterization: a review.

Ductility dip cracking (DDC) is a solid-state failure occurring during multi-pass solidification processes (e.g., welding, additive manufacturing) for FCC alloys that exhibit a distinct dip in their ductility at intermediate temperatures. While the phenomenon has been studied for over a century, the majority of current research focuses on a subset of DDC-susceptible FCC alloys (Ni–Cr–Fe). The review paper herein presents an analysis of published data to evaluate the current state of understanding regarding the materials mechanisms at work. Recent advances in test methods have permitted highly controlled approaches for testing and quantifying DDC, but the wide range of unique tests often provide conflicting results regarding the fundamental materials behaviors and underlying mechanisms. At present, three mechanisms have been proposed for DDC: grain boundary sliding, precipitate-induced strain, and impurity element segregation. While the majority of published studies support grain boundary sliding as the primary mechanism of DDC, an examination of the aggregate data available across multiple studies suggests combinatorial impact of simultaneous (and competing) mechanisms for DDC. Further, the long-held assumptions regarding the negative impact of key alloying elements become less convincing when comparing results across studies. There are considerable future opportunities for research on DDC behaviors in other alloy systems, and there are a lacunae of data when considering the effect of welding process parameters on DDC and the use of modeling and simulation approaches to understand the DDC behavior in the highly susceptible FCC alloy systems. [ABSTRACT FROM AUTHOR]