On the merit of solute segregation and low angle grain boundary for thermal stability and thermal expansion of cold-sprayed CuCrZr

The precipitation hardenable CuCrZr alloy is a potential alternative to copper for inner liners in rocket thrust engines. Cold spray manufacturing has been seen as a promising processing route to manufacture bulk additive structure of CuCrZr. This work reveals that the cold-sprayed as-deposited Cu-Cr-Zr alloy, in its inherent non-equilibrium state, is highly stable up to 950 °C and exhibits lower thermal expansion than the equilibrium Cu-Cr-Zr alloy, deduced using HT-XRD and Thermo-Calc. Atomic-scale compositional and diffraction analysis using Atom Probe Tomography (APT) and Electron Backscatter Diffraction (EBSD) support the Zener pinning effect of Cr segregation near the grain boundaries, along with a large fraction of low-angle grain boundaries (LAGBs), that contribute to the high thermal stability and controlled thermal expansion of the deposit. Cold spray deposition naturally yields microstructural features that are conducive to high thermal stability and controlled thermal expansion, features which are comparable to the self-organized microstructures observed in Segregation engineering (SE).