Novel Functional Behaviors: Beyond Shape Memory Effect & Superelasticity: Session 2
Program Organizers: Ibrahim Karaman, Texas A&M University

Tuesday 10:20 AM
July 11, 2017
Room: Wrigley
Location: Hyatt Regency Chicago

Session Chair: Fei Xiao, Shanghai Jiao Tong University

10:20 AM  
Effect of Microstructure on the Low-cycle Fatigue Properties of a Fe–15Mn–10Cr–8Ni–4Si Austenitic Alloy: Ilya Nikulin1; Takahiro Sawaguchi1; 1National Institute for Materials Science
    Superior low-cycle fatigue (LCF) resistance was observed in high-Mn iron base alloy susceptible to strain induced martensitic (SIM) transformation. In present study the effect of the initial austenitic structure on the low cycle fatigue (LCF) properties and SIM transformation was studied in the Fe-15Mn-10Cr-8Ni-4Si seismic damping alloy under an axial strain control mode with total strain amplitudes, Δεt/2, ranging from 0.7 to 2 %. The microstructures with various grain size and texture conditions were produced by warm rolling followed by annealing at temperatures ranged from 600 to 900°C. It was observed that austenitic grain size ranged from 8 to 95 micron generally does not affect martensitic transformation and the LCF resistance of the studied alloy. However, strong texture produced by low temperature annealing inhibits strain induced phase transformation and reduces fatigue resistance of the studied alloy. The relation between LCF properties, strain-induced martensitic transformation and initial microstructure are discussed.

10:40 AM  
Thermoelastic γ-α'- Martensitic Transformation, Shape Memory Effect and Superelasticity in FeNiCoAlX (X=Ta, Nb, Ti) High-Strength Crystals: Chumlyakov Yuriy1; Kireeva Irina2; Poklonov Vechaslav2; Kuksgausen Irina2; Kuksgausen Dmitry2; Pobedennaya Zinaida2; Panchenko Marina2; Reunova Kseniay2; 1Tomsk State University; 2Tomsk state university
    On single crystals of FeNiCoAlX (X = Ta, Nb, Ti) iron-based alloys the new experimental results on development of thermoelastic martensitic transformations (MT) under stress from fcc γ-phase to bct α'-phase depending on the size of dispersed γ'-phase particles are presented. The necessary conditions for the development of thermoelastic MT are achieved by precipitation of nanometric γ'-phase particles which have coherent lattices coupling with austenite and retain coherency with martensite. For the first time on [001]- oriented single crystals of FeNiCoAlX (X = Ta, Nb, Ti) alloy with γ'- phase particles size of d ≤5 nm the anomalously large reversible deformations equal to 15.3 % are found. These values are greater in 2 times than theoretically calculated values of lattice deformation ε0 at γ-α'-MT. The physical cause of appearance large reversible deformations is established and associated with the development of reversible <110>{110} mechanical twinning in α'-martensite.

11:00 AM  
Behavior of the Thermal Hystereses Associated with Crystalline and Magnetic Phase Transformations of the Ni52Mn25In16Co7 Heusler Alloy with Applied Field: Amila Madiligama1; Pnina Ari-Gur1; Yang Ren2; Vladimir Shavrov3; Victor Koledov3; Alexey Mashirov3; Alexander Kamantsev3; 1Western Michigan University; 2Argonne National Laboratory; 3Kotelnikov Institute of Radio-engineering and Electronics of Russian Academy of Sciences
    Irreversibilities associated with the thermal hystereses of the first-order phase transformations in Ni-Mn based Heusler alloys reduce the amount of useful work or entropy change in each phase transformation cycle. Understanding the behavior of the thermal hystereses associated with both crystalline and magnetic transformations with magnetic field is crucial for optimizing the output. Ni52Mn25In16Co7 Heusler alloy undergoes both crystalline and magnetic phase tranformatins from austenite cubic L21 (Fm¯3m) to a mixture of monoclinic (P 1 2/m 1) martensitic phases (5M and 7M) and from ferromagnetic to a very low magnetization phase, respectively. Phase-fraction analysis and thermomagnetic measurements of this alloy demonstrate thermal hystereses associated with both crystalline and magnetic phase transformations. In the studied magnetic field range (0-6 T), the thermal hysteresis of the structural transformation has a minimum under ~2.8 T while that of the magnetic phase transformation monotonically increases with the magnetic field.

11:20 AM  
Origins of Non-Schmid Behavior in Fe3Al: Experiments and Theory: SERTAN ALKAN1; HUSEYIN SEHITOGLU2; 1University of Illinois at Urbana Champaign ; 2University of Illinois at Urbana Champaign
    In this work, we attempt to identify the fundamental source of the significant deviations from Schmid Law in plastic deformation of DO3 ordered-Fe3Al shape memory intermetallics. The major contributions can be summarized in capsule form as follows: (i) Critical Resolved Shear Stress (CRSS) values are predicted within the framework of modified Peierls-Nabarro formalism supplemented by molecular dynamics/statics simulations. (ii) The differential displacements of the non-planar screw dislocation cores are mapped by molecular statics simulations. (iii) High resolution Digital Image Correlation is utilized to pinpoint CRSS values in single crystals along varying uniaxial loading orientations. The experimental findings have been bridged to the synergy of two main factors: (i) coupling between the external non-glide shear stresses and the core displacements, (ii) asymmetric glide resistances along {112}<111> slip systems. The current approach has been extended to the continuum scale to pave the way for prospective crystal plasticity models incorporating non-Schmid behavior.

11:35 AM  
A Novel Fatigue Crack Detection Method using Magnetic Shape Memory Alloys : Nick Barta1; Ibrahim Karaman1; 1Texas A&M University
    Common nondestructive evaluation techniques are generally restricted to surface investigations, large arrays of sensors, or limited surface penetration. A new method for damage assessment is required that allows for interrogation at any point in the material, on the micron scale. In this way, fatigue cracks could be monitored before they reach critical size. By interacting with stress fields around cracks, embedded magnetic shape memory particles could be forced to undergo martensitic transformation changing their magnetic properties. Currently, we have been able to manufacture high density composites of NiMnCoSn and aluminum 7075 using powder precursors. Bulk material retains the distinct magnetization change of the particles during transformation under low magnetic fields (1 Tesla), despite diffusion occurring between the magnetic sensory particles and the aluminum matrix. Investigations into the effect and composition of the diffusion zone are ongoing, as well as crack-particle interactions.

11:50 AM  
Long-term Superelastic Behaviour and Damping on Cycling at Nano-scale in Cu-Al-Ni Micropillars Array: Jose Fernando Gómez-Cortés1; Jose San Juan1; Maria Luisa Nó1; 1University of the Basque Country
    The superelastic behaviour at nano-scale has been studied during long-term cycling in Cu-Al-Ni micropillars. Several arrays of micropillars were milled by focused ion beam (FIB) technique on [100] oriented Cu-Al-Ni single crystals. All pillars from the array were tested in an instrumented nanoindenter with a 2μm radius sphero-conical diamond indenter at room temperature. The superelastic response was tested over hundreds cycles on all pillars and over several thousands cycles on some randomly selected pillars. The results were analysed from its load-depth curves individually, and comparatively among pillars array. Recoverable and reproducible superelastic behaviour has been obtained during thousands cycling tests on Cu-Al-Ni micro-pillars, and the evolution of characteristic magnitudes during cycling, critical stress and mechanical damping are presented and discussed. These promising results open the door for designing potential applications doing use of 3D dampers of Cu-Al-Ni SMA, which could be integrated in MEMS technology

12:10 PM Break