Interactions of Phase Transformations and Plasticity: Poster Session
Program Organizers: Valery Levitas, Iowa State University

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


P1-23: Critical Analyses on the Instrumented Ultramicrohardness Results on Aging NiTi Alloy in Distinct Phase Fields: RODOLFO DA SILVA TEIXEIRA1; PatrÝcia Freitas Rodrigues2; Fabiana da Silva Santos1; Andersan dos Santos Paula1; Francisco Manuel Braz Fernandes3; 1INSTITUTO MILITAR DE ENGENHARIA; 2Universidade Nova de Lisboa ; 3Universidade Nova de Lisboa
    A study carried out in a Ni-rich Ni–Ti alloy solubilized at 850░C and aged at different times (30, 60 and 90 minutes) at 500║C, aiming to criticize the results of instrumented ultramicrohardness tester (DUH-211S) versus X-Ray Diffraction (XRD) at room temperature from previous heating and cooling according to the respective Differential Scanning Calorimetry (DSC) curves. In addition to evaluating the effects on the presence of phase B2, B19’ and/or R prior to the instrumented ultramicrohardness and the distinct mechanical properties extracted from this technique, the tests were carried out to at differents maximum load in order to define the load to be used for explain the effects of the elastic and plastic deformations during load and unloading, considering that these previous phases can be exhibited during the deformation stress induced transformation - superelasticity; or a B19’ variants rearrangement - shape memory effect.

P1-24: Effect of 4K Cryogenic Tension on the Microstructure of Superlattic Precipitation Strengthen NiMoCr Alloy Haynes 242: Na Min1; Ke Han2; Yan Xin2; 1Shanghai University; 2National High Magnetic Field Laboratory
    High strength at cryogenic temperatures make Haynes 242 an attractive choice for cryogenic applications.Both the ultimate tensile strength and yield strength of this alloy increase at 4K compared with room temperature, without decreasing elongation. After deformation, a large number of deformation twin boundaries appear in the aged samples. Twinning of ordered phase itself also occur since it is sheared by deformation twin during deformation. The ordered phase has been refined to become nanosize Pt2Mo-Type precipitates. Detail TEM observation was carried out to measure the average twin thickness. The results indicate that samples deformed at 4k have larger twin volume fraction and finer twin space than deformed at 298K. More fractions of grains develop secondary twinning system at 4K deformation. The refinement of the structure formed during the cryogenic deformation results in high homogeneous deformation, high strain hardening rate and enhanced mechanical strength in this nickel based alloy.

P1-25: Effect of Thermomechanical Treatment on Pseudoelastic Behavior of Ferromagnetic Fe-Ni-Co-Ti Alloy: Anatoliy Titenko1; Lesya Demchenko2; Larisa Kozlova1; Mustafa Babanli3; 1Institute of Magnetism of National Academy of Sciences and Ministry of Education and Science of Ukraine; 2National Technical Institute of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute"; 3Azerbaijan State University of Oil and Industry
    The search for optimal regimes of cold plastic deformation and subsequent aging to achieve the maximum of pseudoelasticity in the polycrystalline ferromagnetic Fe-27,2%Ni-17,4%Co-5,2%Ti (wt%) alloy was carried out. The mechanical behavior of the alloy under uniaxial tension in a wide temperature range as well as when applying an external magnetic field during the deformation was studied. The alloy consists of both martensite and austenite phase of cooling and/or stain, including two-phase region. A sufficiently high level of superelastic deformation and one-way shape memory effect has been achieved. The preliminary thermomechanical treatment with a compression degree of 7,4-22,5% followed by aging at 650°C favors the alloy deformation along the channels of phase and twin plasticity in the Ms-Af temperature range that results in the optimal combination of superelastic deformation and one-way shape memory effect.

P1-26: Influence of Grain Size on the Work Hardening Behavior of Metastable Austenite in Fe-24Ni-0.3C Alloy : MAO Wenqi1; GAO Si1; BAI Yu1; SHIBATA Akinobu1; TSUJI Nobuhiro1; 1Kyoto University
    The fully recrystallized ultrafine grained (UFG) metastable austenite of Fe-24Ni-0.3C alloy with a mean grain size of 0.5 μm was fabricated by high pressure torsion (HPT) process and subsequent annealing. Mechanical properties of UFG material and as-received material with a mean grain size of 35 μm were investigated by tensile tests at room temperature. It was found that the yielding strength was enhanced significantly by grain refinement, but the ultimate tensile strength and uniform elongation of the UFG and as-received materials were almost the same. The as-received material exhibited the enhanced work-hardening while the work-hardening of UFG material was relatively low. Nanoindentation test and quantitative measurement of martensite volume fraction were carried out at different plastic strain to investigate the effect of grain size and deformation-induced martensitic transformation on work hardening behavior.

P1-27: Modeling the Mechanical Behavior of Tempered Martensite: Edgar Alejandro Pachon Rodriguez1; Artem Arlazarov1; 1ArcelorMittal Global R&D
    The precipitation of carbides and the consequent decrease of carbon in solid solution with tempering were taken into account in the Continuous Composite model for the mechanical behavior of as-quenched martensite, to describe the mechanical behavior of tempered martensite. The model was initially adjusted with only one fitting parameter and the predicted stress-strain curves are in agreement with the experimental ones. The influence of the composition was included in the model using a second fitting parameter providing better agreement with the experimental stress-strain curves.

P1-28: Thermal Cycling Instability of Martensitic Transformation and the Micro−mechanism in Solution−treated Ni51Ti49 Alloy: Caiyou Zeng1; Zhongxun Zhao1; Yuanyuan Li1; Shanshan Cao1; Xiao Ma1; Xin-Ping Zhang1; 1South China University of Technology
    The thermal cycling instability of martensitic transformation in Ni51Ti49 alloy undergoing solution and subsequent water−quench treatments is investigated by differential scanning calorimetric (DSC) cycling. Results show that an increase in the maximum temperature of thermal cycling (Tmax) from 20║C to 100║C leads to a significant increase in the change of peak temperature of martensitic transformation from 0.7║C to 9.7║C after 10 cycles, and correspondingly there is an increased degradation of enthalpy from 0.71W/g to 1.9W/g. A comprehensive microstructural study indicates that the dislocation multiplication associated with the transformation−induced micro−plasticity during the repetitive phase transformation cycling is responsible for the degradation of martensitic transformation stability. Furthermore, an in−depth analysis is performed to deepen the understanding of the mechanism of the temperature−dependent thermal cycling stability based on the interactions among the quenched−in point defects introduced by solution treatment, transformation−induced dislocations and moving phase interfaces under thermal cycling.

P1-29: The Effect of Thermomagnetic Treatment on Structure and Properties of Cu-Al-Mn Shape-Memory Alloys: Anatoliy Titenko1; Lesya Demchenko2; 1Institute of Magnetism of National Academy of Sciences and Ministry of Education and Science of Ukraine; 2National Technical Institute of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute"
     Aging Cu-Mn-Al alloys undergo the thermo-induced martensite transformation and demonstrate shape memory effect. The influence of alloying with Mn as well as regimes of aging of austenite (high-temperature phase) on a subsequent martensite transformation in Cu-Al-Mn alloys was studied. The morphology of martensitic transformation behavior under the annealing in a constant magnetic field with a different sample orientation relatively field and without field was investigated to control the process of martensite induction under the cooling. The temperature dependences of electrical resistance, magnetic susceptibility, and magnetization, as well as the field dependences of magnetization, were found. The alloy phase composition and microhardness were determined. The tendency of oriented growth of the precipitated phase particles in a direction of applied field and the increase of a volume fraction of these particles under the thermomagnetic treatment favors a reversibility of induced martensite transformation.

P1-30: The Influence of α’ (bcc) Martensite on the Dynamic and Magnetic Response of Powder Metallurgy FeMnSiCrNi Shape Memory Alloys: Mihai MOCANU1; Elena MIHALACHE1; Bogdan PRICOP1; Firuta BORZA2; Marian GRIGORAS2; Radu COMANECI1; Burak OZKAL3; Leandru BUJOREANU1; 1"Gheorghe Asachi" Technical University of Iasi; 2National Institute of Research and Development for Technical Physics; 3Istanbul Technical University
    In FeMnSi-based SMAs the “executive” phase is ε (hcp) stress induced martensite which retransforms to γ (fcc) austenite during heating, causing free-recovery shape memory effect (SME). At low Mn content or high deformation degrees, α’ (bcc) martensite can be additionally induced by cooling or deformation, being considered as detrimental for the magnitude of SME. In the case of PM Fe-14Mn-6Si-9Cr-5Ni (wt. %) SMAs, containing 5 fractions of mechanically alloyed powders (0-40 %), solution treated to 5 temperatures (700-1100 deg. C), large amounts of α’ martensite were detected by XRD and observed by SEM. Nevertheless, free-recovery SME was obtained and enhanced by training, up to bending strokes of 24 mm, developed with a rate of 1.71 mm/ 0C. The paper corroborates the qualitative and quantitative evolutions of α’, ε and γ with DMA and thermomagnetic measurements performed on the 25 sets of specimens, during heating up to 500 deg. C.

P1-31: The Wide Hysteresis Mechanism of Ni47Ti44Nb9 Alloy Caused by Nb Addition: Fan Qichao1; 1Chinese Academy of Engineering Physics
    The wide hysteresis mechanism of Ni47Ti44Nb9 alloy caused by Nb addition has been investigated in a detailed way in this research. The whole hysteresis of the alloy is delicately divided into three parts which have been caused by martensite/austenite interface motion, martensite reorientation, and Nb-riched phase, individually. The hysteresis caused by interface resistance increases in mild way as long as the increase of Nb quantity dissolved in the matrix, while the one caused by martensite reorientation sharply rises and contributes to a main part of the whole wide hysteresis. The hysteresis caused by Nb-riched phase first increases in a steady way and then slowly drops with the increase of deformation strain. The influences of Nb-riched phase on the hysteresis are mainly caused by the plastic deformation degree and its contribution to the whole hysteresis is less that of martensite reorientation.