Developing the Additive Manufacturing Chain of AlSi7Mg with Laser Powder Bed Fusion and Tailored Heat Treatments for Railway Spare Parts

Abstract

The use of metal additive manufacturing technologies in railways sector can provide increased flexibility in terms of spare part logistics. Combined with lightweight metals such as Al-alloys, the product performance can also be enhanced in terms of weight reduction, vibration and noise control. The railway sector is more likely to exploit large and bulky parts produced by laser powder bed fusion (LPBF), which should have appropriate mechanical properties. Therefore, the whole production chain should be analyzed considering the heat treatment steps suited for a distributed and resource efficient manufacturing scheme. Accordingly, this work analyzes the additive manufacturing of AlSi7Mg alloy by LPBF and its consecutive heat treatment steps. In particular, the impact of LPBF process productivity, heat treatment type and atmosphere composition were considered to analyze the most appropriate route for the needs of the railways applications. The results show that with an appropriate direct aging treatment in air, mechanical characteristics of the alloy could be improved, despite that the high layer thickness used in LPBF could increase process productivity. The absence of a quenching step was found to be favorable for large parts, while the absence of an inert gas such as Ar in the heat treatment did not generate any reduction in the mechanical properties.