Microstructural length scale manipulation via solidification and its influence on mechanical behavior in a high-strength intermetallic-based eutectic alloy

The present manuscript investigates the yield-strength dependence on the microstructural length scale and solidification rate variation, in an intermetallic-based, high-strength Ni₃Al + Ni₅Zr eutectic alloy. Imposed solidification rates were varied by casting the alloy into molds of different diameter which resulted in a microstructure consisting of two different morphologies (lamellar and non-lamellar eutectic). The consequent change in solidification conditions translated into various microstructural length scale changes, such as colony width, morphology width, morphology fraction, lamellar width, etc. The bulk mechanical properties were estimated and compared as a function of this change. Consequently, this study alludes toward the potential of achieving higher strengths in such microstructures by lowering the fraction of non-lamellar eutectic morphology, which can be achieved by imposing even faster solidification rates on the solidifying melt. This observation, combined with easy castability of this alloy, make it an attractive candidate for fusion-based additive manufacturing processes, where different cross sections of complex geometries often experience very high solidification rates.