scholarly journals Variant Selection in Fe-20Ni-1.8C under Bending

Crystals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 474 ◽  
Author(s):  
Annick Baur ◽  
Cyril Cayron ◽  
Roland Logé
Keyword(s):  
Martensitic Transformation ◽  
Stress Field ◽  
Applied Stress ◽  
Empirical Model ◽  
Phenomenological Theory ◽  
Variant Selection ◽  
Classical Approach ◽  
Martensitic Steels ◽  
Four Point Bending ◽  
Shape Strain

Variant selection is commonly observed in martensitic steels when a stress is applied to the material during transformation. Classically, the selection phenomenon is modelled considering the work of the shape strain in the applied stress field. This shape strain is generally calculated by using the Phenomenological Theory of the Martensite Crystallography (PTMC). In the present study, we studied the martensitic transformation occurring in a Fe-20wt%Ni-1.8wt%C alloy transformed while loaded in four-point bending. A significant variant selection is observed, but surprisingly its nature cannot be explained by the classical approach. A crystallography-based empirical model which accounts for the experimental results is proposed instead.

Predicting the available work from deformation-induced α′′ martensite formation in metastable β Ti alloys

2020 ◽  
Vol 53 (4) ◽  
pp. 1015-1028 ◽  
Author(s):  
Frank Niessen ◽  
Elena V. Pereloma ◽  
Ahmed A. Saleh
Keyword(s):  
Stress State ◽  
Martensitic Transformation ◽  
Applied Stress ◽  
Phenomenological Theory ◽  
Warm Rolling ◽  
Martensite Formation ◽  
Ti Alloys ◽  
Shape Strain ◽  
Bain Strain ◽  
Stress States

Deformation-induced α′′ martensite formation is essential to the mechanical properties of a variety of metastable β Ti alloys by extending elasticity or contributing to work-hardening during plastic deformation. Nevertheless, to date, a comprehensive analysis of the effect of β texture and applied stress state on the martensitic transformation to α′′ is still lacking. The present study therefore provides a detailed analysis of the work which is made available from the shape strain of the martensitic transformation under a variety of in-plane stress states and as a function of β crystal orientation. The available work was found to strongly depend on the applied stress state and the parent grain orientation. The shape strain of the martensitic transformation was obtained from applying the phenomenological theory of martensite crystallography. In cases where this theory was not applicable, an approximation of the shape strain by the Bain strain was found to provide a good approximation of the available work. Analysis of three different metastable β Ti alloys showed no strong effect of the alloy composition on the available work. Martensite formation from typical cold- and warm-rolling β texture components under different stress states is discussed. Cases are highlighted to show how the cold- and warm-rolling β textures can be tailored to hinder martensite formation upon subsequent industrial forming operations.

An Interpretation on Kinetics of Martensitic Transformation

2011 ◽  
Vol 172-174 ◽  
pp. 90-98 ◽  
Author(s):  
Tomoyuki Kakeshita ◽  
Takashi Fukuda ◽  
Yong-Hee Lee
Keyword(s):  
Magnetic Field ◽  
Hydrostatic Pressure ◽  
Martensitic Transformation ◽  
Magnetic Fields ◽  
Martensitic Transformations ◽  
Phenomenological Theory ◽  
Time Dependent ◽  
Isothermal Process ◽  
Kinetics Of ◽  
Transformation Processes

We have investigated athermal and isothermal martensitic transformations (typical displacive transformations) in Fe–Ni, Fe–Ni–Cr, and Ni-Co-Mn-In alloys under magnetic fields and hydrostatic pressures in order to understand the time-dependent nature of martensitic transformation, that is, the kinetics of martensitic transformation. We have confirmed that the two transformation processes are closely related to each other, that is, the athermal process changes to the isothermal process and the isothermal process changes to the athermal one under a hydrostatic pressure or a magnetic field. These findings can be explained by the phenomenological theory, which gives a unified explanation for the two transformation processes previously proposed by our group.

scholarly journals A simple variant selection in stress-driven martensitic transformation

2019 ◽  
Vol 116 (30) ◽  
pp. 14905-14909 ◽  
Author(s):  
Binbin Yue ◽  
Fang Hong ◽  
Naohisa Hirao ◽  
Roman Vasin ◽  
Hans-Rudolf Wenk ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Orthorhombic Phase ◽  
Martensitic Transformations ◽  
Variant Selection ◽  
Structural Distortions ◽  
Orientation Variant ◽  
Diamond Anvil ◽  
Simple Variant ◽  
Pressure Stress

The study of orientation variant selection helps to reveal the mechanism and dynamic process of martensitic transformations driven by temperature or pressure/stress. This is challenging due to the multiple variants which may coexist. While effects of temperature and microstructure in many martensitic transformations have been studied in detail, effects of stress and pressure are much less understood. Here, an in situ variant selection study of Mn2O3 across the cubic-to-orthorhombic martensitic transformation explores orientation variants at pressures up to 51.5 GPa and stresses up to 5.5 GPa, using diamond anvil cells in radial geometry with synchrotron X-ray diffraction. The diamonds not only exert pressure but also impose stress and cause plastic deformation and texture development. The crystal orientation changes were followed in situ and a {110}c 〈001〉c // (100)o 〈010〉o relationship was observed. Only the {110}c plane perpendicular to the stress direction was selected to become (100)o, resulting in a very strong texture of the orthorhombic phase. Contrary to most other martensitic transformations, this study reveals a clear and simple variant selection that is attributed to structural distortions under pressure and stress.

Quantitative Analysis of Variant Selection and Orientation Relationships during the γ-to-α Phase Transformation in Hot-Rolled TRIP Steels

2010 ◽  
Vol 89-91 ◽  
pp. 359-364 ◽  
Author(s):  
Loïc Malet ◽  
Pascal J. Jacques ◽  
Stéphane Godet
Keyword(s):  
Phase Transformation ◽  
Orientation Relationship ◽  
Hot Deformation ◽  
High Performance ◽  
Statistical Treatment ◽  
Phenomenological Theory ◽  
Variant Selection ◽  
Orientation Relationships ◽  
Α Phase ◽  
Hot Rolled

The orientation relationships that apply to the fcc (γ) – bcc (α) phase transformation in high-performance hot-rolled TRIP-aided steels were characterised by EBSD techniques. A statistical treatment of the experimental data allows the mean orientation relationship to be determined. This mean orientation relationship was compared to the models commonly proposed in the literature and confronted qualitatively to the predictions of the phenomenological theory of martensite crystallography (PTMC). The variant selection phenomenon was also characterized quantitatively at the level of individual austenite grains. The reconstruction of the EBSD maps evidences that bainite grows by packets in which the bainite laths share a common {111}γ plane in the austenite. This growth mechanism is not influenced by the prior hot deformation of the austenite. The hot deformation has a critical influence on the number of packets that forms. The analysis of the crystallographic features of the bainite packets reveals that all possible variants are formed in a packet, though in different proportions.

Analysis on the Martensitic Transformation in the Ti-xNb Alloys Using a Phenomenological Theory

2007 ◽  
Vol 124-126 ◽  
pp. 1669-1672 ◽  
Author(s):  
Hi Won Jeong ◽  
Seung Eon Kim ◽  
Chang Yong Jo ◽  
Yong Tae Lee ◽  
Joong Kuen Park
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Martensitic Transformation ◽  
Shape Memory ◽  
Titanium Alloys ◽  
Martensitic Transformations ◽  
Phenomenological Theory ◽  
Transition Elements ◽  
Low Elastic Modulus ◽  
Diffraction Peaks

The titanium alloys containing the Nb transition elements have been investigated as the Ni-free shape memory and the biomedical alloys with a low elastic modulus. The mechanical properties of the alloys depended upon the meta-stable phases like the α`, α``, ω. To study the martensitic transformations from the β to α`` or α` the Ti-xNb (x=0 to 40 wt%) alloys were melted into the button type ingots using a VAR, and followed by the water-quenching after the soaking at 1000oC for 2hrs. The crystallography of the martensitic phases in the water-quenched alloys was analyzed using a XRD. The diffraction peaks of the orthorhombic martensites were identified by the crystallographic relationship with the bcc matrix. The lattice parameters of the orthorhombic martensites were varied continuously with the contents of the Nb elements. The martensitic transformations of the alloys were studied using the phenomenological theory of Bowles and Mackenzie.

Control of Martensitic Morphology in Thermal-Mechanical Processing of Ferrous Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 69-72 ◽  
Author(s):  
Q.P. Meng ◽  
Yong Hua Rong ◽  
T.Y. Hsu
Keyword(s):  
Activation Energy ◽  
Martensitic Transformation ◽  
Theoretical Analysis ◽  
Applied Stress ◽  
Mechanical Processing ◽  
Ferrous Alloys ◽  
Nucleation Barrier

The quantitative relationships are suggested that the applied stress decreases the nucleation barrier and activation energy of nucleation of martensitic transformation, and strain increases the nucleus sites. Taking Fe-20Ni-0.5C and Fe-25Ni-0.66C alloys as examples, their different martensitic morphologies in thermal-mechanical processing can be explained and the origin of such a difference may be revealed based on the above theoretical analysis. Accordingly, the control of martensitic morphologies in thermal-mechanical processing of ferrous alloys will become possible.

Giant room temperature elastocaloric effect of PbTiO3 ferroelectric materials with 90° domain structure

RSC Advances ◽  
2016 ◽  
Vol 6 (74) ◽  
pp. 70557-70562 ◽  
Author(s):  
F. Wang ◽  
B. Li ◽  
Y. Ou ◽  
L. F. Liu ◽  
C. Z. Peng ◽  
...  
Keyword(s):  
Stress Field ◽  
Domain Structure ◽  
Applied Stress ◽  
Room Temperature ◽  
Polarization Switching ◽  
Ferroelectric Materials ◽  
Stress Fields ◽  
Elastocaloric Effect

The elastocaloric effect in PbTiO3 with 90° domain structure under the applied stress field at room temperature has been studied. A negative ΔTσ of −7.2 K can be obtained by controlled polarization switching under the applied stress fields.

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