Low-Defect AM of High Strength Aluminium Alloy by LMD

Abstract

A manifold variety of additive manufacturing techniques has a significant positive impact on many industry sectors. Large components are often manufactured via laser metal deposition (LMD) instead of using powder bed based processes. The advantages of LMD process are a high build-up rate with values up to 300 cm³/h and a nearly limitless build-up volume. In combination with the lightweight material aluminium it is possible to manufacture large lightweight components with geometries adapted to customer requirements in small batches. This contributes the pursuit of higher efficiency of machines through lightweight materials as well as lightweight design. A low-defect additive manufacturing of high strength aluminium EN AW-7075 powder via LMD is an important challenge to concern. During the process a considerable proportion of pores can build which weakens the mechanical properties. Additionally, the heat input affects the hardness of the manufactured part. A significant reduction of pore volume can be achieved by a higher laser power and an improved shielding gas flow. Therefore, a shielding gas shroud was developed to keep atmospheric hydrogen away from the process zone. The combination of the improved shielding gas flow with a high laser power led to a decrease of pore volume from over 7% to lower than 1.5%.