Influence of Heat Flow on the Grain Morphology and Porosity of Wire Arc Additive Manufactured 2319 Aluminum Alloy

Uniform grain morphology and low porosity are the key to obtain better mechanical properties of 2319 aluminum alloy fabricated by wire arc additive manufacture. In this study, the influence of heat flow on the grain morphology and porosity was investigated by experimental and simulation methods. The solidification theory was used to illustrate the columnar-to-equiaxed transition phenomenon and the variation in the volume fractions of different grains. The results show that the deposition layer was composed of fine equiaxed grains in the inter-layer zone, columnar and equiaxed grains in the lower and upper parts the of inner-layer zone, respectively. Furthermore, the volume fractions of the equiaxed and columnar grains were varied by adjusting wire feed rates (WFR). With the higher WFR, the volume fraction of columnar grains decreases, while the porosity and tensile strength first increase and then decrease. The best mechanical properties could be achieved when the WFR was 5.5 m/min, with a tensile strength of 274 MPa and an elongation of 12.5%.