Comparative effect of Mn/Ti solute atoms and TiC/Ni 3 (Al,Ti) nano-particles on work hardening behaviour in Ni-Cu alloys fabricated by wire arc additive manufacturing

Two Ni-Cu alloys with various contents of Mn, Ti, Al and C were deposited in a shape of single-bead multi layered walls using wire arc additive manufacturing technology. To modify solute atom concentrations and particle number density values, the as-welded alloys were subjected to annealing at 1100 °C and age-hardening heat treatment in the 610-480 °C temperature range. Microstructure characterisation was carried out using optical, scanning, conventional transmission and atomic resolution transmission electron microscopy. Work hardening behaviour was studied using tensile testing. For similar deposition and heat treatment conditions, an alloy with higher C and Al, and lower Mn contents exhibited a higher number density of >20 nm TiC particles, higher number density of γ′-Ni 3 (Al, Ti) particles, and, associated with these, superior hardness, tensile strength, strain hardening rate and toughness. The comparative effect of solid solution and precipitation strengthening on work hardening behaviour and fracture mode is discussed.