Comparative analysis of structure and mechanical properties of parts produced by electron-beam additive manufacturing and cold metal transfer

Abstract

Currently, the most prospective industry development areas are prototyping and additive manufacturing. In contrast to more precise powder technologies, faster wire technologies providing non-porous products are of great interest. This paper contains a comparative analysis of the effect of two wire technologies – electron-beam additive manufacturing and cold metal transfer – on the structure and mechanical properties of Aluminum Alloy 5056. Electron beam power is close to arc power at optimal printing parameters, but cold metal transfer is cheaper due to the impulse nature of the arc. In addition, the arc method is implemented in an argon atmosphere, and this accelerates the applied layer cooling. In general, the grain structure of the material is refined due to the lower heat transfer and accelerated cooling. This results in increased strength and microhardness. The constant heat removal from the substrate and the increase in the product weight change thermal conditions of the following layer. This is controlled by beam/arc powder reduction, but each layer has its own thermal history affecting the structure and properties. In particular, the more heat is transferred to the layer from the previous layers, the less strong it is. When a certain height (about 30 mm) is passed, cooling is intensified by the large mass of the product and the strength is increased again. This is most characteristic for cold metal transfer. However, these fluctuations are rather small. Mechanical properties along the growth direction are highly stable in both technologies. Cold metal transfer also shows less alloying magnesium burn-off. In general, currently the cold metal transfer technology is more cost effective and provides better quality products.