On the Impact of Additive Manufacturing Processes on the Microstructure and Magnetic Properties of Co–Ni–Ga Shape Memory Heusler Alloys

Abstract

Ferromagnetic shape memory alloys (FMSMAs) show a large magnetic fieldinduced strain up to 10%, [1,2] which makes this materials interesting for magnetic actuators. [3] A promising material class for FMSMAs are Heusler alloys, such as Ni-Mn-X (X: Ga, In, Sn, Al), [2,[4][5][6][7][8] Ni-Fe-Ga, [9] or Co-Ni-X (X: Al, Ga), [10][11][12] exhibiting a large shape memory effect owing to a reversible martensitic transformation. The investigated Co-Ni-Ga Heusler alloy undergoes a first-order magnetostructural transformation (FOMST) from hightemperature B2-ordered austenite to lowtemperature tetragonal L1 0 martensite. [13] A fully reversible superelastic response as well as excellent cyclic stability up to temperatures of 373 K has been reported for single crystals. [12] However, polycrystalline Co-Ni-Ga as well as other polycrystalline Heusler alloys suffer from intergranular cracking and premature failure after several transformation cycles due to the anisotropic volume change of randomly orientated grains. [14,15]

The role of NiTi shape memory alloys in quality of life improvement through medical advancements: A comprehensive review

“…198–203 The impacts of AM processes on the SMA characteristics and properties are also being explored in depth. 204–207 The fatigue modeling of SMAs fabricated through AM is another topic of interest with many recent and ongoing studies. Multiscale multiphysics modeling approaches have been explored to study the thermal simulation and microstructural evolution of additively manufactured NiTi alloys.…”

The FALCON double-detector Laue diffractometer add-on for grain mapping at POLDI

“…This results in premature failure at grain boundaries and intergranular cracking under thermo-mechanical loading, attributed to the high density of grain boundaries and triple points within the samples, as well as the anisotropic volume change displayed by randomly oriented grains. To address this challenge, several processing techniques have been tested to improve the mechanical properties of polycrystalline samples (Vollmer et al, 2015;Lauhoff et al, 2022;Scheibel et al, 2022). Among these techniques, hot extrusion stands out, which involves heating the material above its recrystallization temperature and forcing it through a die to achieve the desired shape (Karsten et al, 2019;Niendorf et al, 2019).…”

Influence of Colloidal Additivation with Surfactant‐Free Laser‐Generated Metal Nanoparticles on the Microstructure of Suction‐Cast Nd–Fe–B Alloy

“…[5,10] In AlSi10Mg alloys, the fast cooling rates result in an ultrafine supersaturated Si-rich network inside each grain which positively influences the corrosion behavior; however, high residual stresses and microstructural inhomogeneity negatively affect further mechanical properties like ductility and fatigue resistance. [7,11,12] Yet, compared with structural materials (e.g., 316L, AlSi10Mg, and Ti6Al4V), functional materials such as magnetic shape memory alloys (e.g., Ni-Mn-In or Co-Ni-Ga [13] ), magnetocaloric materials, or rare-earth permanent magnets (e.g., Nd-Fe-B [14,15] ) are rarely produced with PBF-LB/M; thus, further research is necessary to correlate the melting-induced microstructures with the functional read-out in as-built parts. [13,16,17] The desirable microstructure for high coercivity in, e.g., Nd-Fe-B alloys consists of submicrometer-or micrometer-sized Nd 2 Fe 14 B grains isolated by a paramagnetic grain boundary phase.…”

“…[7,11,12] Yet, compared with structural materials (e.g., 316L, AlSi10Mg, and Ti6Al4V), functional materials such as magnetic shape memory alloys (e.g., Ni-Mn-In or Co-Ni-Ga [13] ), magnetocaloric materials, or rare-earth permanent magnets (e.g., Nd-Fe-B [14,15] ) are rarely produced with PBF-LB/M; thus, further research is necessary to correlate the melting-induced microstructures with the functional read-out in as-built parts. [13,16,17] The desirable microstructure for high coercivity in, e.g., Nd-Fe-B alloys consists of submicrometer-or micrometer-sized Nd 2 Fe 14 B grains isolated by a paramagnetic grain boundary phase. [15,18,19] Currently, the microstructure achieved by conventional manufacturing, as applied through sintered, hot-deformed, or hydrogenation disproportionation desorption and recombination (HDDR) Nd-Fe-B magnets, cannot be achieved by PBF-LB/M.…”