Creep Properties and Deformation Mechanism of Additively Manufactured NiAl‐CrMo Composites

In contrast to directionally solidified NiAl‐CrMo in situ composites, additively manufactured specimens show a significant increase in the interface and cell boundary density. Understanding the resulting deformation structures in electron beam powder bed fusion processed NiAl‐CrMo is important to optimize the creep performance. At lower temperatures of 700°C and higher loads, the additively manufactured material exhibited a behavior consistent with power law creep, characterized by a notably high creep exponent. This suggests the dominance of dislocation activity, particularly the shearing of the CrMo _ss reinforcement phase within the composite, facilitated by knitting reactions of dislocations at the interfacial dislocation network. Conversely, at reduced loads and elevated temperatures of 800°C–900°C, the deformation mechanism shifted, as evidenced by inhomogeneous deformation and pore formation at vertical cell boundaries. In this regime, the climb of (001)‐type dislocations was prevalent. The transition between these mechanisms appears to be strongly linked to the notably high density of cell boundaries after additive manufacturing. At higher temperatures, the shift towards a diffusive creep mechanism deteriorates the mechanical properties of additively manufactured NiAl‐CrMo composites. However, exceptionally high creep strength is observed in the intermediate temperature regime, demonstrating the potential of additively manufactured NiAl‐CrMo in situ composites.