Enhanced mechanical properties in nickel-aluminium bronze alloy via wire arc additive manufacturing with follow-weld forced cooling

In pursuit of enhanced microstructural and mechanical properties, follow-weld forced cooling wire arc additive manufacturing (CWAAM) was employed for the fabrication of nickel aluminium bronze (NAB) components. The application of compressed gas metal arc welding (GMAW) system was implemented to mitigate the interference of cooling gas with the arc. A comprehensive examination of the microstructural and mechanical was conducted with and without the cooling source. Compared to WAAM sample, the grains size in CWAAM decreased by more than two times, attributed to higher melt pool subcooling. The 100 texture in CWAAM specimens showed a decrease due to the emergence of equiaxed grains and grain refinement, reducing the anisotropy of materials. Moreover, the dislocation density in CWAAM samples increased by 62.7%, owing to forced cooling that generated additional dislocations and suppressed recrystallization. Consequently, the average 0.2% yield strength (338.7 MPa) and ultimate tensile strength (687.3 MPa) of CWAAM specimens exhibited an approximate increase of 20% and 8.6%, respectively, in comparison to WAAM samples. This enhancement in yield strength is primarily ascribed to grain boundary strengthening and dislocation strengthening, instead of solid solution strengthening or precipitation strengthening.