Determination of Annealing Temperature of Thin-Walled Samples from Al-Mn-Mg-Ti-Zr Alloys for Mechanical Properties Restoration of Defective Parts After SLM

The aim of this work is to investigate the effect of annealing (at temperatures ranging from 260 °C to 530 °C) of thin-walled Al-Mn-Mg-Ti-Zr samples manufactured by selective laser melting (SLM) on their tensile mechanical properties, hardness, and surface roughness. The results of this study may contribute to the development of post-processing modes for thin-walled products made of corrosion-resistant aluminum alloys with increased strength, manufactured using SLM technology. Hierarchical clustering methods allowed us to identify three groups of thin-walled samples with different strain-hardening mechanisms depending on the annealing temperature. The greatest hardening is achieved in the first group of samples annealed at 530 °C. Metallographic analysis showed that at this heat treatment temperature, there are practically no micropores (macrodefects) and microcracks. X-ray phase analysis showed the precipitation of Ti and Zr, as well as the formation of an intermetallic phase with a composition of Mg8Al16. At lower heat treatment temperatures, from 260 °C to 500 °C, the observed hardening is statistically significantly lower than at 530 °C. This phenomenon, combined with the formation of intermetallic phases and the precipitation of titanium/zirconium, contributes to the hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM. The main results of this study show that the optimal strain hardening of thin-walled Al-Mn-Mg-Ti-Zr alloy samples manufactured by SLM is achieved by heat treatment at 530 °C for 1 h. The strengthening mechanism has two characteristics: (1) dispersion strengthening due to the formation of precipitates and (2) reduction in macrodefects at high temperatures.