TY - JOUR

T1 - Microstructural Investigation of a FeMnAlNi Shape Memory Alloy Processed by Tungsten Inert Gas Wire and Arc Additive Manufacturing

AU - Viebranz, Vincent Fabian

AU - Hassel, Thomas

AU - Maier, Hans Jürgen

N1 - Funding information: This research was funded by DEUTSCHE FORSCHUNGSGEMEINSCHAFT, grant number 401738767. The material was processed by thyssenkrupp Steel Europe AG (Duisburg, Germany). The APC was funded by Open Access Fund of Leibniz Universität Hannover.

PY - 2022/10/16

Y1 - 2022/10/16

N2 - In the present study, tungsten inert gas wire and arc additive manufacturing was used to process an iron-based FeMnAlNi shape memory alloy. By a layer-by-layer method, a wall structure with a length of 60 mm and a height of 40 mm was generated. Bidirectional welding ensured grain growth parallel to the building direction. To maintain a nearly constant temperature–time path upon cooling, the structure was fully cooled after each weld to room temperature (298 K). With this approach, an anisotropic microstructure with a grain length of up to 8 mm (major axis) could be established. The grain morphology and formed phases were investigated by optical microscopy and scanning electron microscopy. The images revealed a difference in the orientation with respect to the building direction of the primarily formed γ grains along the grain boundaries and the secondarily formed γ grains in the heat-affected zones. Subgrains in the α matrix were observed also by scanning electron microscopy. With X-ray diffraction, the preferred orientation of the α grains with respect to the building direction was found to be near 〈100〉. Overall, an anisotropic polycrystalline material with a columnar texture could be produced, with a preferred grain orientation promising high values of transformation strains.

AB - In the present study, tungsten inert gas wire and arc additive manufacturing was used to process an iron-based FeMnAlNi shape memory alloy. By a layer-by-layer method, a wall structure with a length of 60 mm and a height of 40 mm was generated. Bidirectional welding ensured grain growth parallel to the building direction. To maintain a nearly constant temperature–time path upon cooling, the structure was fully cooled after each weld to room temperature (298 K). With this approach, an anisotropic microstructure with a grain length of up to 8 mm (major axis) could be established. The grain morphology and formed phases were investigated by optical microscopy and scanning electron microscopy. The images revealed a difference in the orientation with respect to the building direction of the primarily formed γ grains along the grain boundaries and the secondarily formed γ grains in the heat-affected zones. Subgrains in the α matrix were observed also by scanning electron microscopy. With X-ray diffraction, the preferred orientation of the α grains with respect to the building direction was found to be near 〈100〉. Overall, an anisotropic polycrystalline material with a columnar texture could be produced, with a preferred grain orientation promising high values of transformation strains.

KW - FeMnAlNi

KW - grain morphology

KW - iron-based shape memory alloy

KW - microstructure

KW - texture

KW - thermomagnetization

KW - tungsten inert gas welding

KW - wire and arc additive manufacturing

UR - http://www.scopus.com/inward/record.url?scp=85140736473&partnerID=8YFLogxK

U2 - 10.3390/met12101731

DO - 10.3390/met12101731

M3 - Article

AN - SCOPUS:85140736473

VL - 12

JO - Metals

JF - Metals

SN - 2075-4701

IS - 10

M1 - 1731

ER -