Advanced Processing Techniques: Additive, Porous, and Others: Session 3
Program Organizers: Aaron Stebner, Colorado School of Mines

Thursday 10:20 AM
July 13, 2017
Room: Comiskey
Location: Hyatt Regency Chicago

Session Chair: Jan Van Humbeeck, KU Leuven-MTM

10:20 AM  Invited
Additive Manufacturing of Magnetic Shape-Memory Alloys and Magnetocaloric Materials: An Overview: Markus Chmielus1; Erica Stevens1; Jakub Toman1; Amir Mostafaei1; 1University of Pittsburgh
    Additive manufacturing (also known as 3D printing) is becoming mainstream for the production of small batches of plastic parts and prototyping and is currently transforming the metal manufacturing world through never before possible complex shapes and new combinations of materials. Magnetic shape memory alloys (MSMA) and magnetocaloric materials (MCM) are currently only produced by traditional manufacturing techniques. Therefore, additive manufacturing will expand application possibilities for these materials via advanced geometries, designed composition gradients, multiscale porosity and easier and more controlled manufacturing. In this talk, we will discuss the advantages and disadvantages of additive manufacturing methods – such as Directed Energy Deposition (DED) and Binder Jet Printing (BJP) with subsequent processing – for functional Heusler alloys (MSMA and MCM). Furthermore, we will describe how printing and processing parameters as well as modifications to the BJP and DED processes influence and improve the microstructure (e.g. highly textured) and functionality.

11:00 AM  
Process-microstructure-property Relationships in Additively Manufactured Fe-based Shape Memory Alloys: Thomas Niendorf1; Christian Lauhoff1; Malte Vollmer1; Philipp Krooss1; Florian Brenne1; 1University of Kassel
    Additive manufacturing (AM), also referred to as 3D-printing, currently is in focus of numerous industrial branches as it has the potential to revolutionize industrial production. For structural materials such as Ti-6Al-4V and stainless steels data reporting on process-microstructure-property relationships are available in literature. However, shape memory alloys (SMAs) only have been analyzed scarcely. Novel Fe-based shape memory alloys show excellent pseudoelastic behaviour in single- and oligocrystalline condition. In the current work laser beam melting is employed to manufacture bulk samples from Fe-Mn-Al-Ni pre-alloyed powder. Microstructures in as-built condition and upon post-processing annealing treatment were characterized by electron microscopy. Nano scale precipitates crucially needed for thermoelastic martensitic transformation were induced by aging treatments. The results of the current study clearly reveal that good pseudoelastic behaviour can be obtained in the AM Fe-based SMAs. The roadmap for optimization of performance is deduced from the results presented.

11:20 AM  
A Coupled Framework for the Location-specific Design of Shape Memory Functionality in NiTi Based Additive Manufacturing: Luke Johnson1; Kubra Karayagiz1; Ji Ma1; Brian Franco1; Gustavo Tapia1; Alaa Elwany1; Ibrahim Karaman1; Raymundo Arroyave1; 1Texas A&M University
    Additive manufacturing approaches enable accurate control of complex part geometries and most powder-feed style AM even allow for the design of spatial variations in composition. This ability to functionally grade parts is particularly interesting in NiTi shape memory alloys where there is a well established strong relationship between martensitic start temperature and nickel concentration in the matrix phase. Unfortunately, powder feed mechanisms incur additional costs and may not be precise enough to accurately control the martensitic start temperatures. This presentation details the modeling of an alternative solution for powder-bed style machines which spatially varies laser processing parameters to affect precipitation of Ni-rich precipitates locally, thereby changing the composition of the matrix and martensitic start temperature. The framework couples finite-element thermal modeling simulations with a thermodynamic and kinetic based precipitate evolution model to predict precipitate volume fraction in a fabricated part. Both models were calibrated with experimental data.

11:35 AM  
Assessing and Controlling the Variability of Additively Manufactured NiTi: Brian Franco1; Gustavo Tapia1; Kubra Karayagiz1; Ji Ma1; Alaa Elwaany1; Raymundo Arroyave1; Ibrahim Karaman1; 1Texas A&M University
    Variability in the performance and properties of additively manufactured metal alloys is a major issue for widespread adoption in industries that have strict certification requirements (such as the biomedical and aerospace industries). Quantifying these variabilities is a technically difficult enterprise, requiring many different characterization techniques and a large number of repeated experiments. We show that by exploiting the shape memory effect, NiTi can be used as a sensory material in order to observe microstructural and compositional variability in samples prepared by selective laser melting. This method has the advantage of being simple, cost effective, and less time consuming than conventional techniques. As a case study, differential scanning calorimetry (DSC) is used to show that reducing the distance between successive laser passes is highly effective at reducing the compositional and microstructural variability in both the localized sense (inhomogeneity in a single part) and the repeatability sense (bulk differences in multiple parts).

11:50 AM  
Ultra-high Damping and Ductility of Bimodal Porous TiNi-based Shape Memory Alloys by Composite with Ti2Ni Phase during Wide Temperature Range: Bin Yuan1; Bing Yang1; 1South China University of Technology
    A bimodal of 400 um and 120 um irregular pores, porous TiNi-Ti2Ni shape memory alloy composite (SMAC) with 59% porosity was fabricated by sintering of Ti-46at.%Ni powder and pore-forming agent. The microstructure, mechanical properties and damping capacity were characterized by scanning electronic microscopy, compressive testing and dynamic mechanical analyzer. Ti2Ni particles with 1-3 um are homogeneously distributed in the TiNi matrix. The porous TiNi-Ti2Ni SMAC exhibits exceptional high damping capacity of 0.25 at room temperature, it is the best results for the reported porous/dense SMA or SMA composites to our knowledge. Moreover, the porous SMAC at relatively low strain amplitude can exhibit ultra-high damping capacity of at least 0.06 during wide temperature range of -90~200oC, which resulted from the stress concentration of pores and the massive interfaces between pore/matrix and TiNi/Ti2Ni. This porous SMAC is considered as an ideal candidate for use as a light-weight damping materials in energy-saving applications.