High Temperature Mechanical Properties of AlMgScZr Alloy Produced by Laser Powder Bed Fusion

Abstract

The present work is focused on the fracture behavior of Scalmalloy®, an AlMgScZr alloy specifically developed for laser powder bed fusion (L-PBF) process. This material has gained increasing attention for applications requiring high performances due to its outstanding properties and low anisotropic behavior. The responsible for the high specific properties of the alloy is its microstructure, characterized by fine grains and the presence of Al3(Sc,Zr) precipitates as well as nano-sized oxides. These particles form during the L-PBF process and act as nucleation sites for grain refinement. They have been also found to exhibit relevant thermal stability. An increase in strength is achieved from the further formation of smaller Al3(Sc,Zr) precipitates during the annealing treatment at 325°C, which is a typical post treatment for this alloy.The fracture mechanism of AlMgScZr alloy has rarely been studied so far, especially at high temperature or after high temperature exposure. In the present work, samples were produced via L-PBF and annealed. Tensile tests were then performed at different testing temperatures, i.e. 25°C, 100°C, 150°C. Furthermore, samples were tested both under annealed condition and after soaking at 100°C, 150°C, 200°C for 10 h. Mechanical properties were evaluated, and the fracture surface morphology was observed under scanning electron microscope to analyze the failure mechanism. Differential scanning calorimetry analyses were also performed to verify the thermal stability of precipitates. The correlation between these results and the mechanical properties allowed the investigation of the fracture behavior evolution with temperature. This provided a comprehensive characterization of the high temperature mechanical properties of AlMgScZr alloy, useful for evaluating new high temperature applications.