The influence of the characteristic microstructure of additively manufactured AlSi10Mg on the plastic behaviour at various strain rates

Abstract

Additively manufactured (AM) lightweight metallic structures subjected to impact attract growing interest, for biomedical, defence, and aerospace applications. Understanding their mechanical response under various strain rates is essential to design and optimise them. Currently, the strain rate influence on the behaviour of AM materials is still not fully elucidated, nor is the corresponding metallurgical aspect. This research presents a comprehensive study on the influence of the microstructure and anisotropy of AlSi10Mg specimens made by Laser Powder Bed Fusion (l-PBF) on their behaviour under various strain rates. Tensile specimens were fabricated in three orientations and tested at 0.001 s−1, 1 s−1, 500 s−1, and 1000 s−1 strain rates using a universal testing machine, intermediate strain rate mechanical device, and Split Hopkinson Pressure bar, respectively, combined with Digital Image Correlation. Fractography analysis revealed how the various dynamic loadings affected the failure modes and the corresponding microstructural evolution. Despite presenting low strain rate sensitivity and no evidence of strain hardening, the strain rate influenced the fracture response and elongation to failure. For higher strain rates, microstructural changes were captured on the fracture surfaces, suggesting a localised in-situ thermal treatment due to the adiabatic effect of high velocity loadings.

Keywords

• AlSi10Mg
• Hopkinson Bar
• Microstructure
• Laser Powder Bed Fusion
• Impact
• Strain Rate Sensitivity