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Expert Insight

Cyclic deformation behavior of Invar alloy manufactured by direct energy deposition

Fe-Ni alloys with a Ni concentration of approximately 36 wt.-% are well-known for their low coefficients of thermal expansion (CTE) near room temperature. Due to the low CTE and excellent mechanical properties in cryogenic environment, Invar alloys are commonly used as a high precision and highly reliable material in components where superior dimensional stability is required.

As a result of high ductility and pronounced work hardening combined with a low heat conductivity, conventional processing and machining of Invar is challenging and related to high tool wear. Additive manufacturing (AM) techniques represent powerful and promising candidates to overcome these challenges as they enable a tool-free near-net shape production of complex freeform components. Since many components made of Invar, e.g. precision optics instruments, are used under very complex loading regimes, often including cyclic loads, the performance under fatigue loading needs to be investigated. Therefore, the present study provides insights on the structural integrity of Fe-Ni Invar alloy processed by wire-based direct energy deposition utilizing either a laser-beam (DED-LB) or an electric arc (DED-Arc) as energy source. The fatigue lives under strain-controlled fully reversed loading are discussed with respect to the initial microstructure, the corresponding mechanical properties under tensile loading, fractographic analyses as well as the mechanical properties the cyclic deformation response including the stress-strain hysteresis.

The speaker is:
Dr.-Ing. Johannes Günther, Group Leader Welding/Direct Energy Deposition, Günter-Köhler-Institut für Fügetechnik und Werkstoffprüfung GmbH, ifw jena


  • Forschung und Entwicklung