To investigate the microstructural evolution of wrought-nickel-based superalloy GH4169 from the original ingot to the finished product of manufacturing processes, different kinds of etchants and etching methods were used to show the fine precipitates and their morphologies. The obtained microstructures can vary in size, type, distribution, location, formation, and interactions of multiple phases, which were observed and analyzed by optical microscopy (OM), scanning electron microscopy (SEM), and an energy dispersive spectrometer (EDS). The dendrite segregation behavior of as-cast superalloy GH4169 was investigated. In addition, the microstructural evolution mechanism of second-phase particles during dynamic recrystallization was analyzed. This work sheds light on the evolution of the second-phase structure of nickel-based superalloys during the preparation process, providing guidance for process development and visual interpretation of the relationships between microstructure and properties.

Continuous innovation in the design of metallic materials is essential for further progress in aerospace, automotive, construction, and shipping. Fine grain strengthening is considered to increase the strength of metals without losing plasticity. However, many fabrication techniques are restricted to very small sizes. Recently, the introduction of in situ nanoparticles with coherent or semi-coherent interfaces in the metallic matrix achieves simultaneous enhancement of the strength and ductility of metallic materials. In this review, the focus is on fabrication techniques and the formation mechanism of nanoparticles and nanoclusters in metal materials. The effects of nanoparticles on grain refinement, inhibiting segregation, second phase, and inclusion refinement are discussed, and the mechanism of simultaneous improvement in the strength and ductility of nanostructured metal materials is briefly covered. Finally, we provide a summary and outline of the possible direction for further advances in this research field.