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

Monday 5:30 PM
July 10, 2017
Room: Crystal Ballroom A
Location: Hyatt Regency Chicago

P1-1: A Novel Micro-nano Dual-scale Porous Cu-Zn-Al Shape Memory Alloy Composite Current Collector with a Layer of β and Cu on the Ligament by One-step Dealloying Method: Luo Zheng1; Yuan Bin1; 1South China University of Technology
    A novel micro-nano dual-scale porous Cu-Zn-Al composite with a layer of β phase shape memory alloy and nano-size Cu on the ligament was fabricated by one-step dealloying of Cu-34Zn-6Al precursor with a dual β and γ phase in a HCl-FeCl3 solution and subsequent heat treatment. The pore and microstructure evolutions during dealloying and heat treatment were studied by XRD, SEM and TEM. The formation of micro- and nano- porous structure is attributed to the dealloying of γ phase and preferential dissolution of Zn and Al atoms in the β phase. During subsequent heat treatment, the diffusion of zinc and aluminum atoms can be clearly observed and a new layer of β phase emerges on the ligament, also the dual-scale porous structure can be well preserved after heat treatment. The dual-scale porous composite is an ideal candidate as current collector in a lithium-ion battery with high capacity and cycling life.

P1-2: Anisotropic Deformation and Different Mechanisms of Superplasticity in Polycrystalline Ni-Mn-Ga Alloys under Uniaxial Tension: Longsha Wei1; Xuexi Zhang1; Mingfang Qian1; Lin Geng1; 1Harbin institute of technology
    Ni–Mn–Ga alloys have for decades received attention owing to their multi-functional properties such as magnetic-field-induced strain. However, such alloys are extremely brittle at ambient temperature. Here, we present a polycrystalline Ni47.4Mn31.5Ga21.1 alloy, exhibiting strongly anisotropic deformation and excellent superplastic capacity with different microstructures. For the columnar grains along <001> obtained at as-cast state, Ni47.4Mn31.5Ga21.1 alloy exhibits brittle fracture at loading axis perpendicular to <001> direction and ductile behavior over 100% elongation at parallel to <001> direction at 700C. However, Ni47.4Mn31.5Ga21.1 alloy displays ductile behavior in two directions with different flow stress at 800C. The superplastic mechanism is attributed to dislocation glide and dynamic recovery with maximum elongation of 137%. For the extruded rod with equiaxed grains and <111> texture, the superplastic mechanism is dislocation glide and dynamic recrystallization with maximum elongation of 319%. The present work opens a realistic sight to fabricate complex engineering components by superplastic deformation.

P1-3: Binder Jet 3D Printing of Magnetocaloric Materials: Katerina Kimes1; Erica Stevens1; Jakub Toman1; Amir Mostafaei1; Markus Chmielus1; 1University of Pittsburgh
    Magnetocaloric (MC) materials have been intensely studied due to their ability of exhibiting a large adiabatic temperature change when magnetized. This positions them uniquely for the use in magnetic refrigeration, which is more efficient than traditional refrigeration. This study focuses on the characterization of Powder Bed Binder Jet (PB-BJ) printing of MC foams. Alloys studied include Ni-based Heusler alloys. Samples are printed using a custom-designed printer for small amounts of powder. The feedstock powder composition, microstructure, martensite phase transformation, magnetic and magnetocaloric properties are characterized and compared to printed and sintered samples. We will further report the influence of the sintering temperature on densification, porosity characteristics, magnetization, hierarchical twinning and compositional variations throughout particles especially at their surfaces. Entropy data are calculated from temperature-dependent magnetization measurements to compare the magnetocaloric effects of additively manufactured MC materials to bulk MC materials.

P1-4: Contact Pressure and Residual Strain of Resistance Spot Welding on Mild Steel Sheet Metal: Yuanxun Wang1; Yiping Chen1; 1Huazhong University of Science and Technology
    Coupled electrical-thermal and thermo-elastic-plastic analyses were performed to analyze the behavior of the mechanical features during the resistance spot welding (RSW) process including the squeeze, heating and hold steps, and to prepare for further structural analysis for large complex structure with large quantity of resistance spot welds. A two-dimensional axisymmetric thermo-elastic–plastic FEM model was developed and analyzed in the commercial FEM program, ANSYS. The analysis was based on the transient temperature field obtained from a transient electrical–thermal simulation of RSW process conducted by the authors. The distribution and change of the contact pressure at the electrode–workpiece interface and faying surface, the residual stress and residual plastic strain distribution of the weldment were obtained through the analysis.

P1-7: Mechanical Properties of Highly Porous Ti-based Shape Memory Alloys: Yeon-wook Kim1; Hyuck-jun Gwon1; Jae-won Jang1; 1Keimyung University
    Porous Ti alloys has been considered as one of the promising biomaterials in surgical implants. In this study, Ti-based shape memory alloy fibers were fabricated by a melt overflow technique. The as-solidified fibers were cut into segments and uniformly put into the predetermined packing chamber of the mold pressing equipment. Sintering was carried out in vacuum induction furnace under a high vacuum atmosphere. Then porous Ti-Ni-Mo bulks with 75% porosity were successfully synthesized with a large pore size and three-dimensional network morphology. Compressive stress-strain curve of the porous alloy showed that the plateau of the stress-strain curve was observed at about 1.5 MPa and the strain of the stress-plateau associated with the stress-induced martensitic transformation was more than 5% and the elastic modulus was as small as about 2 GPa. This small elastic modulus is ascribed to the high porosity of Ti-based shape memory alloys.

P1-8: Microstructural Evolution and Magnetic Properties of Binder Jet Additive Manufactured Ni-Mn-Ga Magnetic Shape Memory Alloy Foam: Amir Mostafaei1; Katerina Kimes1; Erica Stevens1; Jakub Toman1; Yuval Krimer1; Kari Ullakko2; Markus Chmielus1; 1University of Pittsburgh; 2Lappeenranta University of Technology
    In this study, we investigated microstructural evolution, phase transformation and magnetic behavior of binder jet additive manufactured magnetic shape memory alloy foam. Pre-alloyed angular Ni-Mn-Ga powders have been binder jet printed (BJP) and sintered under controlled conditions, in vacuum and argon. Porosity of the manufactured foams was studied using micro-computed x-ray tomography and found that the relative density of the sintered parts was between 50 and 60%. While samples sintered in vacuum, showed large composition gradients and no phase transformation around room temperature, electron microscopy observations and elemental analyses showed no compositional gradient in the BJP sample sintered in argon atmosphere. The samples sintered in argon atmosphere also showed 10M modulated martensite similar to the pre-alloyed powder determined via x-ray diffraction. Differential scanning calorimetry and thermomagnetic results showed a martensitic transformation just above room temperature. Furthermore, we will present the response of the samples to applied magnetic fields.

P1-9: Structure, Functional and Mechanical Properties of Surface Composite Layers Made of Multicomponent Materials based on TiNi with a Gradient of Phase Transformation Temperatures : Zhesfina Blednova1; Peter Rusinov1; Etibar Balaev1; 1Kuban State Technological University
    We described the model structure and architecture of multi-functional multi-layer surface composition made of multicomponent materials with shape memory effect, which is based on TiNi and has significantly different temperatures of phase transformations. We carried out integrated formation technology of surface composition using patented equipment in the conditions of complex high-energy impacts, including mechanical activation of applied powder material, high-velocity oxygen-fuel spraying with subsequent thermo-mechanical processing in a single vacuum cycle. The sequence of functional layers’ deposition, their composition, thickness, structure-phase state and dispersity are determined by operating conditions and controlled by processing modes. We carried out modeling of the main formation stages of the surface composition and determined the main characteristics that define the operating properties: grain size, porosity, reversibility of deformation, adhesion, micro-hardness, fatigue strength, vitality.

P1-11: Superelastic Behavior of Rapidly Solidified Ti–Zr–Nb-Sn Alloys: Shuanglei Li1; Yeon-wook Kim2; Tae-hyun Nam1; 1Gyeongsang National University; 2Keimyung University
    Ti-18Zr-12.5Nb-2Sn, Ti-18Zr-11Nb-3Sn, Ti-18Zr-9.5Nb-4Sn (at.%) alloy fibers were fabricated by rapidly solidification method and superelastic properties were studied by using tensile test. All of as-spun alloy fibers are composed of β phase and a small amount of α" martensite. Recovery strain of 3.85% for 4% pre-strain was observed at room temperature in Ti-18Zr-12.5Nb-2Sn (at.%) alloy fibers and the martensitic transformation start temperature (Ms) estimated by stress-strain curves was about 170 K. The effect of cyclic deformation on superelasticity was also investigated in Ti-18Zr-12.5Nb-2Sn (at.%) alloy fibers. Stable superelstic behavior and a narrow stress hysteresis of 35 MPa were observed in the as-spun alloy fibers at room temperature. Ti-18Zr-12.5Nb-2Sn (at.%) alloy fibers annealed at 673 K and 773 K are composed of β + α phases due to a part of β phase transform into α phase during annealing heat treatment.

P1-10: Processing Exploration of SiC Fiber Reinforced Biomedical Porous Ti-based Shape Memory Alloy: xu zhou1; wu jie1; gao yan1; 1South China University of Technology
    As a bone replacement material of metal matrix, high porosity Ti-based shape memory alloy has better biocompatibility and more matching elastic modulus than the bulk or low porosity counterpart. However, high porosity structure will lead to strength decrease of the alloy, which is a critical problem to be solved. In this study, SiC fiber reinforced porous TiNb-based composites were fabricated by vacuum powder sintering method, using the biocompatible SiC fibers (diameter≈10um). In order to avoid the interface reactions between SiC fibers and Ti matrix during high temperature sintering, SiC fibers were coated with BN. The dispersion process of SiC fibers, the mixing process of SiC fibers into TiNb powders and the sintering process were mainly investigated and the balance among matrix strength, elastic modulus and superelasticity of the porous SiC / TiNb composite was obtained.