Properties of a superelastic NiTi shape memory alloy using laser powder bed fusion and adaptive scanning strategies

Abstract

A NiTi shape memory alloy with the nominal composition Ni50.9Ti49.1 (at%) was processed by laser beam melting/laser powder bed fusion and the process parameters as well as the type of scanning strategy (point-like exposure) were optimized in a first step to obtain delicate lattice structures (strut diameters below 200 µm). In the second step, the lattice structures were analyzed by means of optical and electron microscopy as well as computer tomography to obtain the interrelation between the process parameters, strut diameter and the uniformity of the corresponding struts. The processing, especially the laser power and the type of point-like exposure, has a strong influence on the resulting strut diameter and, therefore, on the haptic stiffness of lattice structures and the mechanical properties (deformability, superelasticity). Unlike other approaches, our findings imply that filigree NiTi lattices with high uniformity can be manufactured on a standard industry laser powder bed fusion machine without modifying its hard- or software configuration.

Biological Cell Investigation of Structured Nitinol Surfaces for the Functionalization of Implants

“…In contrast to new 3D printing techniques, it is currently impossible to reduce the size of the structures further, as the resulting surface adhesion between the base of the titanium pyramids and the SMA sheet would be too small. However, this technology opens up the opportunity for future research approaches that may potentially also allow printing of SMA material onto SMA sheets [ 29 , 30 ]. This seems to have great potential due to the enhanced surface adhesion between materials with identical or similar properties.…”

Radiographic Visibility Limit of Pores in Metal Powder for Additive Manufacturing

“…However, it makes a difference if a single big pore or multiple very small pores create the total porosity of the AM part, as from mechanical testing it is known that the parts commonly crack at the biggest pores present [38]. Filigree and delicate AM parts, e.g., lattice structures, are especially endangered [26]. Whether a certain pore size or defect distribution is critical or not may also depend on the material, heat treatment, number of defects, arrangement of defects, location of the pores (close to surface or not), part geometry, and mechanical load.…”

“…However, in the present article, instead of collecting projections from different angles of the powder sample for a reconstruction of a 3D tomographic dataset, 2D radiographs of single layers of the powder are used for inspection. In practice, this would later require that, e.g., a conveyor belt-like or particle stream apparatus is used for moving the particles into the inspection region, similar to the ones used in light scattering devices or direct imaging devices for powder, like a commercial Camsizer ® (Microtrac Retsch GmbH, Haan, Germany) [22,25,26]. For the study presented here, a metal alloy is used, but the pore imaging principle applies to other materials, as well.…”

3D and 4D Printing of Complex Structures of FeMnSi‐Based Shape Memory Alloy Using Laser Powder Bed Fusion

“…In recent years, numerous efforts have been devoted toward the development of unique 3D structures with additional functionalities. [ 1–3 ] In this type of fusion technique, called 4D printing, functionality can be induced by adding a fourth axis to 3D spatial axes. [ 4 ] In particular, many researchers have attempted the combination of structural functionalities with the inherent functionalities of shape memory materials to achieve shape change or to induce the shape memory effect (SME).…”