Excellent strength and thermal expansion behavior of Invar alloy fabricated by in-situ rolling-assisted laser directed energy deposition

Invar 36 alloy samples were fabricated using the in-situ rolling-assisted laser directed energy deposition (LDED) process, and the effect of in-situ rolling on the microstructure, mechanical properties and coefficient of thermal expansion (CTE) was investigated. The plastic deformation introduced by in-situ rolling facilitated the recovery and recrystallization of the pre-solidified layers. The yield strength was significantly enhanced due to grain refinement strengthening and work hardening. The refinement of grains and the increase in residual stress induced by in-situ rolling enabled these samples to maintain an ultra-low CTE.