Shape memory and mechanical properties of a Fe-Mn-Si-based shape memory alloy: Effect of crystallographic texture generated during additive manufacturing

Abstract

The fcc-γ → hcp-ε → bcc-α' martensitic transformation of a Fe-Mn-Si-based shape memory alloy fabricated by laser powder bed fusion (LPBF) is studied for the first time by in-situ neutron diffraction, in-situ high-resolution electron backscatter diffraction and digital image correlation during uniaxial tensile testing. The comparison between horizontal specimens (fabricated with no inclination on the build platform) and vertical specimens (fabricated with 90° inclination on the build platform) shows that sample orientation affects the deformation and transformation behavior of the material, considerably influencing alloy's shape memory and mechanical properties. The reason for the variation in the alloy's behavior is found in the distinct crystallographic texture generated during the LPBF process. In the vertical samples, the preferential 〈110〉 orientation of grains along the loading direction facilitates the martensitic transformation, resulting in enhanced shape memory properties and pronounced work hardening.

Keywords

• Shape memory alloy
• Laser powder bed fusion
• Neutron diffraction
• Martensitic transformation