Colloquia

Samenvatting

Friction Screw Extrusion Additive Manufacturing (FSEAM) is a novel solid-state additive manufacturing method created at the University of Twente. FSEAM is designed to print large aluminium structural components without reaching the melting temperatures, thereby avoiding challenges observed with the melting and solidification of aluminium alloys in fusion-based additive manufacturing methods. Current studies with FSEAM mostly focused on AA6060, a medium strength-aluminium alloy. However, the growing demand for high-strength, lightweight structural components in aerospace applications has led to the current exploratory study on FSEAM fabrication employing the high strength AA7075 aluminium alloy.

The thesis studied the effect of process parameters, tool geometry and heat treatment on the mechanical and microstructural properties of AA7075 printed with FSEAM. Various experiments were conducted at modest printing velocities ranging from 100 mm/min to 150 mm/min. Experiments were performed with a standard threaded tool with a flat bottom as well as with one equipped with tool pins, designed to enhance layer-to-layer bonding. Compared to AA6060, AA7075 proved more difficult to print, possibly due to its higher strength, larger alloy content and stronger sensitivity of the strengthening precipitates to thermal cycles experienced during FSEAM.

Results showed that AA7075 could successfully be printed at 100 mm/min and 150 mm/min with the flat tool bottom and up to 100 mm/min with the tool equipped with pins. The latter tool resulted in a build with sufficient interlayer bonding and good mechanical properties. Post-deposition heat treatments showed that pre-deposition mechanical properties could be restored, giving potential for future aerospace applications.