Splits in metallic materials: A critical review

Splits are delaminations that can occur in metallic alloys during mechanical laboratory testing or under operational conditions in real-world structures. This review provides a comprehensive overview, analysis, and discussion of key contributions to the understanding of split phenomena in metallic alloys, addressing well-established concepts, contextualizing recent developments, and highlighting unresolved questions surrounding this phenomenon.

The review begins by introducing the use of the term “delamination” in materials science and engineering. Subsequently, the classification of delamination types is explored. While the primary focus of this critical review is on splits, certain aspects of other types of delaminations are also briefly discussed. Emphasis is placed on the occurrence of splits in pipeline materials, given the significant impact of this phenomenon. The factors contributing to delamination events in metallic materials with current and potential applications in critical industries are examined in detail. Furthermore, the interpretation of delamination events in the mechanical behavior of metals is thoroughly analyzed through various mechanical tests, including tensile tests, Charpy-V notch tests, drop-weight tear tests, and fracture toughness tests, with a special focus on their implications for structural integrity.

Morphological and geometric characteristics of splits in fracture mechanics specimens are reviewed by analyzing recently published tomography results. The phenomenon of split toughening, and delamination toughening more broadly, is explained, and recent trends in leveraging split toughening to design and produce metallic alloys with superior strength and toughness are contextualized. Finally, the role of split events in hydrogen embrittlement is discussed, highlighting contradictory interpretations of splits in this context.