Solid-State Additive Manufacturing of Al-7075 Alloy by MELD for High Strength Applications

Industrial interest to utilize additive manufacturing (AM) processes for fabrication of large scale and near-net shape parts has largely increased in past few decades. Most melt-based AM processes require use of powders in vacuum chambers or inert environment. Post processing, such as HIP or sintering, is an additional step for most melt-based AM processes due to the presence of defects created during the rapid solidification process. MELD is a solid-state AM process that can use off-shelf materials to print near net shape and large-scale components. These components, produced by the MELD process, are fully dense and have less distortion/residual stress in comparison to most other metal AM technologies.

High strength aluminum alloys have been widely used in the aerospace industry for structural and defense applications. The poor weldability of 7xxx alloys is a common concern while using conventional fusion welding due to intermetallic formation, solidification defects, and component distortion. MELD is a unique technology which avoids the traditional welding/repair challenges by keeping the deposited material in the solid-state during printing.

Al-7075 has been successfully printed using MELD in an open atmosphere. In this work, the microstructure evolution and tensile properties of the as-printed and heat-treated parts will be discussed. The effect of processing temperature on microstructure and mechanical properties are investigated. The MELD process resulted in a fully recrystallized material with an ultra-fine grain structure. The heat-treated MELD deposit, in both T6 and T73 tempers, met or exceeded the mechanical properties stated in standard specifications for 7075 wrought products.