Mikrostrukturelle Charakterisierung einer lichtbogenbasiert additiv gefertigten FeMnAlNi-Formgedächtnislegierung

Microstructural characterization of an arc-based additively manufactured FeMnAlNi shape memory alloy

authored by: Vincent Fabian Viebranz
supervised by: Hans Jürgen Maier
Abstract: The use of shape memory alloys for the reinforcement and stiffening of existing steel structures offer promising approaches to extending service life and improving resource efficiency, particularly in seismically active regions. Fe-based shape memory alloys, such as Fe43.5Mn34Al15Ni7.5, are characterized by cost-effective production, advantageous forming and welding properties, and low temperature dependence of the transformation stress. The applications of NiTi shape memory alloys are limited by their high temperature sensitivity, whereas the FeMnAlNi alloy can be used across a broad temperature range from 77 K to 513 K, meeting the operating temperature requirements of ASTM 709 for structural steel. The martensitic solid-phase transformation (α→γ‘) of the FeMnAlNi alloy enables the dissipation of deformation energy and provides for large so called pseudoelastic deformation. To maximize damping performance, anisotropic, load-direction-oriented microstructures are required, which can be generated through additive manufacturing using arc- and wire-based processes. The process inherent directional solidification results in a coarse-grained and textured microstructure, enhancing the reversibility and damping properties of the alloy. This study evaluated the welding properties of a quaternary FeMnAlNi shape memory alloy during tungsten inert gas and metal inert gas welding with respect to phase fractions and grain morphology. The insights gained were transferred to wire arc additive manufacturing. Subsequently, a comprehensive analysis of the damping properties of additively manufactured, polycrystalline FeMnAlNi alloy was conducted, considering texture, precipitates, grain morphology, and phase fractions. This enabled the assessment of the influence of repeated heat input and the associated solidification morphologies and textures during additive manufacturing on pseudoelasticity and martensitic transformation. Ultimately, these investigations aim to demonstrate the potential of microstructure-oriented manufacturing for understanding the microstructure-property relationships in the production of polycrystalline damping elements based on FeMnAlNi alloys.
Organisation(s): Institute of Materials Science
Type: Doctoral thesis
No. of pages: 160
Publication date: 01.10.2025
Publication status: Published
Sustainable Development Goals: SDG 8 - Decent Work and Economic Growth, SDG 12 - Responsible Consumption and Production
Electronic version(s): https://doi.org/10.15488/19725 (Access: Unknown)