scholarly journals Effect of Specimen Size on the Variant Selection in Martensitic Transformation

1990 ◽  
Vol 12 (4) ◽  
pp. 189-197 ◽  
Author(s):  
Hirofumi Miyaji ◽  
Ei-Ichi Furubayashi
Keyword(s):  
Martensitic Transformation ◽  
Thin Sheet ◽  
Parent Phase ◽  
Variant Selection ◽  
Strain Component ◽  
Selection Models ◽  
X Ray ◽  
Ni Alloy ◽  
Cold Rolling And Annealing ◽  
Constraint Stress

In thin sheet the anisotropy of the internal stress due to constraint by the surrounding parent phase which will be abbreviated as “constraint stress,” seems to occur during the martensitic transformation and the variant selection is expected also in the transformation without external stress. To verify this, the textures were measured by X-ray pole figure method on the γ and α phase which were developed in thin sheet of Fe-30 Ni alloy prepared by severe cold rolling and annealing followed by subzero quenching to liquid Nitrogen. Experimental data were analyzed with conventional variant selection models. The results obtained are as follows: (a) Variant selection phenomenon was clearly observed and the results could be explained with conventional variant selection models. (b) It is expected that different results occur between the conventional variant selection models when the martensitic transformation occurs accompanying the strain component of |ε1|≦|ε2|, where ε1 is the strain along the Bain compression axis and ε2 is along the perpendicular axis.

scholarly journals Transformation Texture Analysis of BCC and BCT Ferrous Martensite

1993 ◽  
Vol 22 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Hirofumi Miyaji ◽  
Ei-Ichi Furubayashi
Keyword(s):  
Crystal Orientation ◽  
Thin Sheet ◽  
Parent Phase ◽  
External Stress ◽  
Strain Component ◽  
X Ray ◽  
Transformation Texture ◽  
Twinning Shear ◽  
Constraint Stress ◽  
Bain Strain

The theoretical prediction of transformation textures, that developed in thin sheet without external stress, was carried out based on the Bain-Strain and Twinning-Shear model, respectively. To examine the validity of the prediction, the experiments were conducted with X-ray pole figure method on Fe-30Ni and Fe-30Ni-0.8C alloy sheets. The results obtained are as follows:(1) Variant selection phenomenon depends on the crystal orientation of the parent phase and on the Bain strain in the martensitic transformation.(2) The effect of the anisotropic constraint stress on the shear deformation involved in the lattice change and on the Bain distortion appears most remarkably in the BCT martensite transformed from the cube textured parent phase.(3) It became clear that such a variant that has the largest Bain strain component to the sheet normal, that is, the variant, of which the Bain distortion is prevented least of all by the anisotropic constraint stress, forms predominantly.

The Martensitic Transformation and Extra Reflections Appearing Prior to the Transformation in AuCd Alloy

1996 ◽  
Vol 459 ◽  
Author(s):  
T. Ohba ◽  
K. Otsuka
Keyword(s):  
Martensitic Transformation ◽  
Synchrotron Radiation ◽  
Experimental Error ◽  
Parent Phase ◽  
Phonon Softening ◽  
X Ray ◽  
X Ray Scattering ◽  
Structure Factors ◽  
Small Crystals ◽  
Crystal Structural

ABSTRACTAuCd alloy is a typical martensitic alloy. The crystal structural of the ζ2' (trogonal) martensite was recently determined and the analysis indicated the possibility of phonon softening. Despite a large absorption coefficient of Cd phonon softening was actually observed by using an isotope 114Cd. In the present study, precise x-ray scattering studies were performed with a rotating anode x-ray source and synchrotron radiation at Photon Factory in KEK, using small crystals. The structure factors of the parent phase and the diffraction profiles along <110> direction were measured with four circle diffractometers. The structure factors decrease when approaching the transformation temperature. Superstructure reflections were observed prior to the onset of the transformation. They are very weak and rather sharp and appear at q = (1/3,1/3,0) within the experimental error, i. e. at the commensurate position.

Martensitic Transformation of TiAu Shape Memory Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 1541-1544 ◽  
Author(s):  
Hideki Hosoda ◽  
Ryosuke Tachi ◽  
Tomonari Inamura ◽  
Kenji Wakashima ◽  
Shuichi Miyazaki
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Parent Phase ◽  
Stoichiometric Composition ◽  
Transformation Strain ◽  
Martensite Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Rich Side

Martensitic transformation temperatures were measured and transformation strains were evaluated in a promising high temperature shape memory alloy TiAu with a compositional range from 46 to 53mol%Au. It was found by differential scanning calorimetry that martensitic transformation start temperature (Ms) is kept almost constant value of 880K in the Au-rich side of the stoichiometric composition. On the other hand, Ms decreases monotonically with decreasing Au content in the Au-poor side. X-ray diffraction analysis revealed that apparent phase of all the alloys at room temperature is B19 martensite phase. Under an assumption that the atomic volume is constant during martensitic transformation, the lattice parameters of B2 parent phase and maximum transformation strain were calculated. It was found that the maximum transformation strain depends on chemical composition and that it reaches 10.75% for Ti-53mol%Au alloy. The value is comparable to that of Ti-Ni.

Relationship between Particle Size and Martensitic Transformation in an Fe-30at%Ni Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 146-149 ◽  
Author(s):  
J.M. Nam ◽  
Tomoyuki Terai ◽  
Masashi Mino ◽  
Y. Aikawa ◽  
Tomoyuki Kakeshita
Keyword(s):  
Particle Size ◽  
Martensitic Transformation ◽  
Driving Force ◽  
Cluster Size ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ni Alloy ◽  
Effect Of Particle Size ◽  
Isothermal Martensitic Transformation ◽  
Scanning Electron

We have investigated the effect of particle size on martensitic transformation by using single crystalline specimens of an Fe-30at%Ni alloy by scanning electron microscope (SEM) observation, X-ray diffraction(XRD), magnetic susceptibility and magnetization measurements. As a result, we have found that an athermal martensitic transformation changes to an isothermal martensitic transformation with decreasing particle size. Considering the result of the TTT diagram, we have estimated the driving force for the martensitic transformation and the cluster size for nucleation of the isothermal martensitic transformation based on the model previously proposed.

Phase Transformations on Aging Cu-Al-Ni β Phase Alloys

1983 ◽  
Vol 21 ◽  
Author(s):  
S. W. Husain ◽  
P. C. Clapp ◽  
M. Ahmed
Keyword(s):  
Martensitic Transformation ◽  
Phase Transformations ◽  
Parent Phase ◽  
Isothermal Kinetics ◽  
X Ray Diffraction ◽  
Subsequent Aging ◽  
X Ray ◽  
Β Phase ◽  
Transmission Electron ◽  
Equilibrium Phases

ABSTRACTThe phase transformations occurring on quenching and subsequent aging of a Cu-Al-Ni β phase alloy have been studied using transmission electron microscopy, x-ray diffraction and optical microscopy. Quenching produces an ordered solid solution, β1, based on the DO3 structure of Cu3A1. X-ray and electron diffraction show satellite diffraction peaks. On aging, these satellite peaks disappear and the parent phase undergoes a martensitic transformation. It is suggested that the parent phase undergoes a process of phase separation through the mechanism of spinodal decomposition before the martensitic transformation occurs. The martensitic transformation shows isothermal kinetics for which a transformation diagram is presented. Prolonged aging results in the formation of equilibrium phases.

Martensitic Transformation and Related Properties of AuTi-FeTi Pseudobinary Alloys

2014 ◽  
Vol 922 ◽  
pp. 25-30 ◽  
Author(s):  
Taku Aoki ◽  
Masaki Tahara ◽  
Kenji Goto ◽  
Yoko Yamabe-Mitarai ◽  
Hiroyasu Kanetaka ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Parent Phase ◽  
Tensile Tests ◽  
Martensite Phase ◽  
Lattice Deformation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Fe Content ◽  
Fe Addition

The effects of Fe addition on martensitic transformation and mechanical properties of AuTi were investigated in this study. It was found that B2 parent phase is stabilized by the Fe addition and that AuTi can contain at least 20mol%Fe. The lattice deformation strain evaluated from θ-2θ X-ray diffraction analysis (XRD) is not significantly changed by the Fe addition. The decrease in Ms evaluated by differential scanning calorimetry (DSC) is-40K/mol%Fe. Tensile tests revealed that, with increasing Fe content, the yield stress decreases up to about 13mol%Fe, largely increases up to 15mol%Fe and then decreases gradually. By taking into account XRD and DSC results, these behaviors are judged to correspond to reorientation of martensite variants, stress induced martensitic transformation and slip deformation of parent phase, respectively. The values of dσSIMT/dCFe and dσSIMT/dT are evaluated to be-170MPa/mol%Fe and-4.3MPa/K, respectively. The elongation is degraded with increasing Fe content from 8% in AuTi (0mol%Fe, martensite phase) to 2% in AuTi-20mol%Fe (parent phase) depending on the apparent phase.

Evidence for ordered Fe3Ni

1987 ◽  
Vol 45 ◽  
pp. 216-217
Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein
Keyword(s):  
Experimental Data ◽  
Martensitic Transformation ◽  
Electron Diffraction ◽  
Room Temperature ◽  
Direct Evidence ◽  
Transformation Product ◽  
Iron Meteorites ◽  
X Ray ◽  
Ni Content ◽  
Temperature Transformation

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.

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