Understanding the grain refinement mechanisms in aluminium 2319 alloy produced by wire arc additive manufacturing

Controlling the grain size and morphology during fusion-based additive manufacturing remains a challenge for many alloys. This work investigates Titanium diboride (TiB2) nucleant particle addition to the high strength Aluminium 2319 alloy produced during wire arc additive manufacturing (WAAM). Two Cold Metal Transfer (CMT) processing conditions are explored (low heat input CMT and high heat input CMT) and the effectiveness of the grain refiner is studied. The addition of TiB2 is found to refine the average equiaxed grain size by up to 22% compared to the non-inoculated alloy. The Interdependence Model is applied to understand the grain refinement mechanisms occurring in low heat input AM technologies in alloys containing powerful growth restricting solutes such as Al 2319.