Additive Manufacturing of Functional and Energy Materials: Shape Memory Alloys
Sponsored by: TMS: Additive Manufacturing Committee
Program Organizers: Sneha Prabha Narra, Carnegie Mellon University; Markus Chmielus, University of Pittsburgh; Mohammad Elahinia, University of Toledo; Reginald Hamilton, Pennsylvania State University
Wednesday 2:00 PM
February 26, 2020
Room: 7B
Location: San Diego Convention Ctr
Session Chair: Sneha Prabha Narra, Carnegie Mellon University
2:00 PM Invited
Additive Manufacturing of NiTi Shape Memory Materials: Steven Storck1; Morgan Trexler1; Andrew Lennon1; Ian McCue1; Tim Montalbano1; Douglas Trigg1; Ryan Carter1; 1Johns Hopkins Applied Physics Laboratory
Additive manufacturing (AM) has the capability to revolutionize the way shape memory metals are used due to the unique ability to create complex geometry and modify microstructure with laser parameters spatially. This work has been focused on solving the fundamental research challenges associated with designing and additively manufacturing functional, stimulus-responsive components from NiTi shape memory alloys via selective laser melting (SLM). A ground up approach was used starting a single track analysis and working through a full parameter set to produce dense nitinol components. Substrate interactions were analyzed to establish conditions that produce correct stoichiometry even on highly mismatched substrate chemistry. The ability to produce large complex geometry shape memory components on Ti64 substrates will be discussed. In addition the ability to tune processing parameters to impact the overall shape memory response will be discussed to achieve a tailorable actuation in a complex geometry.
2:30 PM
Additive Manufacturing of Nitinol with Post Heat Treatment Characteristics: Jeongwoo Lee1; Yung Shin1; 1Purdue University
Nitinol has been widely studied for its shape-memory and super-elastic characteristics. Due to such special mechanical properties, Nitinol has become one of the most promising shape-memory materials for various applications in engineering fields. In this work, Nitinol structures were synthesized in a fully dense form using an additive manufacturing method using the elemental powders to arrive at the prescribed final chemical compositions. The effects of post heat treatment conditions (time and temperature) and overall chemical composition on the shape-memory characteristics of Nitinol were studied systematically to achieve a good core material suitable for various applications. The transformation temperatures of Nitinol samples were controlled accurately by less than 5°C away from the target by changing post heat treatment conditions. Synthesized structures are analyzed via various microstructure characterization techniques and their shape memory capabilities are demonstrated.
2:50 PM
Microstructure-property Correlations of LENS Processed NiTi: Sujith S1; Lakhindra Marandi1; Mitun Das2; Indrani Sen1; 1Academic; 2Government National Research Laboratory
NiTi based alloys having pseudo-elastic properties are popular candidates for different niche applications such as cardio-vascular stents and sensors. Additive manufacturing is a state-of-the-art technique to produce such complex shapes. Mechanical behavior including pseudo-elasticity of NiTi alloy, prepared by laser engineered net shaping (LENS) is investigated thoroughly in the present research. Laser energy densities of the manufacturing method are modified. Corresponding effects on microstructure and phase evolution of the NiTi are evaluated systematically. Subsequently, mechanical properties are assessed by implementing macro-, micro- and nano-indentations with load levels varying over five orders of magnitude and indenter tip geometry varying from sharp-Berkovich to blunt-spherical. Increasing laser energy density of manufacturing is noted to affect the phase evolution leading to improved hardness but reduced pseudo-elasticity. The study provides a scope to optimize the parameters of LENS to manufacture NiTi with the best combination of microstructure, porosity, phase stability as well as pseudoelasticity.
3:10 PM
Fabrication and Functional Properties of Selectively Laser Melted NiTi Lattice Structures Using Point Scanning Strategies: Tobias Gustmann1; Hannes Korn1; Peter Koch2; Ralph Stelzer2; Welf-Guntram Drossel1; 1Fraunhofer IWU; 2TU Dresden
Near-equiatomic NiTi-alloys are attractive materials for medical applications due to their functional properties (pseudoelasticity). However, most of the manufacturing steps needed for processing of NiTi are challenging. Thus, laser beam melting (LBM) was used and identified as a suitable method for the fabrication of a wide range of complex NiTi structures with low impurity pick up and good functional properties. Besides obtaining as-built parts with pronounced shape-recovery, efforts have been made to improve the quality of the processed specimens (e.g. accuracy). In our work, we demonstrate that delicate NiTi lattice structures can be manufactured on a conventional LBM machine using point scanning strategies. Process parameters and the type of point exposure have been optimized to obtain struts (below 200 microns) with high evenness and smooth surfaces. Due to this reason, the use of point scanning strategies is a promising approach for LBM of NiTi lattices with improved mechanical properties.
3:30 PM Break
3:50 PM Invited
The Next Generation of NiTi-based Shape Memory Alloys: Developed for Additive Manufacturing: Behnam Amin-Ahmadi1; Sen Liu1; Sean Mills1; Branden Kappes1; Ronald Noebe2; Aaron Stebner1; 1Colorado School of Mines; 2NASA Glenn Research Center
Binary nickel-titanium shape memory alloys (SMAs) developed for wrought manufacturing processes require extensive amounts of cold work to achieve good mechanical performances. Cold working is undesirable in additive manufacturing. To meet this gap, a suite of precipitation hardenable NiTiHf SMAs have been developed for additive manufacturing to span superelastic, actuation, and structural/tribology performances. The metallurgy, thermomechanical properties, applications, and the first laser powder bed fusion process-structure-property relationships of these alloys will be presented. Furthermore, these alloys promise a means for printing multi-functional structures from a single material – the path forward to such technologies will be discussed.
4:20 PM Invited
Complexity and Opportunities in Additive Manufactured NiTi-based Shape Memory Alloys: Ibrahim Karaman1; Lei Xue1; Bing Zhang1; Kadri Atli1; Alaa Elwany1; Raymundo Arroyave1; 1Texas A&M University
NiTi-based shape memory alloys created through additive manufacturing (AM) techniques such as selective laser melting and direct energy deposition show complex functional behavior and often heterogeneous microstructures that are highly sensitive to the processing parameters. While such sensitivity may pose some challenges in the application of the material, it also creates opportunities for insights into the processing-microstructure-property relationships of AM techniques as well as creating materials with novel functionalities. As examples, we discuss the opportunities brought about by creating controlled location-dependent functional response in a single 3-D printed part, application of AM NiTi as a sensory material for exploring microstructure-related variability in metallic AM processes, and development of an accelerated process parameter optimization framework to fabricate defect free functional AM parts.
4:50 PM
Selective Laser Melting of Co-Ni-Ga Shape Memory Alloys: Philipp Krooss1; Christian Lauhoff1; Julia Richter1; Florian Brenne1; Thomas Niendorf1; 1University of Kassel
Shape memory alloys (SMAs) are known for their their unique material properties. However, binary Ni Ti SMAs suffer from limited application temperature range. To overcome current limitations, high temperature SMAs, i.e. Ni-Ti-X (X= Zr, Hf), Ti-Ta-Al and Co-Ni-Ga, have been introduced. Co-Ni-Ga polycrystals suffer from intergranular constraints. Thus, crystallographic orientation and grain boundary engineering play an important role in terms of functional reversibility. Whereas grain boundary triple junctions promote functional degradation, bamboo-like microstructures result in excellent reversibility. Additive manufacturing allows for direct microstructure design, i.e. realization of globular and columnar-grained structures as well as distinct crystallographic texture. The present study focuses on selective laser melting of Co-Ni-Ga and compares differently processed microstructures. Detailed microstructure analysis using in-situ techniques and electron microscopy was conducted allowing for correlations between the phase transformation characteristics and microstructural features.