scholarly journals Measurement and prediction of the transformation strain that controls ductility and toughness in advanced steels

2020 ◽  
Vol 200 ◽  
pp. 246-255
Author(s):  
Francesco Maresca ◽  
Efthymios Polatidis ◽  
Miroslav Šmíd ◽  
Helena Van Swygenhoven ◽  
William A. Curtin
Keyword(s):  
Transformation Strain

The Effect of Cobalt on Martensitic Toughening Parameters in NiAl

1988 ◽  
Vol 133 ◽  
Author(s):  
Scott M. Russell ◽  
C. C. Law ◽  
M. J. Blackburn
Keyword(s):  
Martensitic Transformation ◽  
Ambient Temperature ◽  
Transformation Temperature ◽  
Transformation Strain ◽  
Temperature Hysteresis ◽  
Transformation Toughening ◽  
Strain Anisotropy ◽  
Interfacial Mobility

ABSTRACTThe martensitic transformation and the effect of cobalt additions on important martensitic toughening parameters are being studied as a means of toughening NiAl alloys. Cobalt additions to NiAl martensite are seen to lower the Ms temperature, reduce the transformation strain anisotropy, and reduce the transformation temperature hysteresis (an indicator of interfacial mobility). Optimization of these parameters should allow martensitic transformation toughening processes to aid in overcoming the ambient temperature brittleness of NiAl alloys.

scholarly journals The dynamic generalization of the Eshelby inclusion problem and its static limit

2016 ◽  
Vol 472 (2191) ◽  
pp. 20160256 ◽  
Author(s):  
Luqun Ni ◽  
Xanthippi Markenscoff
Keyword(s):  
Integral Form ◽  
Transformation Strain ◽  
The Self ◽  
Eshelby Tensor ◽  
Inclusion Problem ◽  
Static Limit ◽  
Governing System ◽  
Eshelby Inclusion ◽  
Interior Domain ◽  
Eshelby Problem

The dynamic generalization of the celebrated Eshelby inclusion with transformation strain is the (subsonically) self-similarly expanding ellipsoidal inclusion starting from the zero dimension. The solution of the governing system of partial differential equations was obtained recently by Ni & Markenscoff (In press. J. Mech. Phys. Solids ( doi:10.1016/j.jmps.2016.02.025 )) on the basis of the Radon transformation, while here an alternative method is presented. In the self-similarly expanding motion, the Eshelby property of constant constrained strain is valid in the interior domain of the expanding ellipsoid where the particle velocity vanishes (lacuna). The dynamic Eshelby tensor is obtained in integral form. From it, the static Eshelby tensor is obtained by a limiting procedure, as the axes' expansion velocities tend to zero and time to infinity, while their product is equal to the length of the static axis. This makes the Eshelby problem the limit of its dynamic generalization.

Modeling the Diffusion-Controlled Growth of Needle and Plate-Shaped Precipitates

2002 ◽  
Vol 731 ◽  
Author(s):  
Z. Guo ◽  
W. Sha
Keyword(s):  
Free Energy ◽  
Transformation Strain ◽  
Interfacial Free Energy ◽  
Growth Theory ◽  
Controlled Growth ◽  
Precipitate Morphology ◽  
Interface Kinetics ◽  
Diffusion Controlled ◽  
Precipitate Growth ◽  
Strain Stress

AbstractVarious theories have been developed to describe the diffusion-controlled growth of precipitates with shapes approximating needles or plates. The most comprehensive one is due to Ivantsov, Horvay and Cahn, and Trivedi (HIT theory), where all the factors that may influence the precipitate growth, i.e. diffusion, interface kinetics and capillarity, are accounted for within one equation. However, HIT theory was developed based on assumptions that transformation strain/stress and interfacial free energy are isotropic, which are not true in most of the real systems. An improved growth theory of precipitates of needle and plate shapes was developed in the present study. A new concept, the compression ratio, was introduced to account for influences from the anisotropy of transformation strain/stress and interfacial free energy on the precipitate morphology. Experimental evidence supports such compression effect. Precipitate growth kinetics were quantified using this concept. The improved HIT theory (IHIT theory) was then applied to study the growth of Widmanstatten austenite in ferrite in Fe-C-Mn steels. The calculated results agree well with the experimental observations.

Transformation Textures in Unstable Austenitic Steel

2002 ◽  
Vol 125 (1) ◽  
pp. 12-17 ◽  
Author(s):  
R. Kubler ◽  
M. Berveiller ◽  
M. Cherkaoui ◽  
K. Inal
Keyword(s):  
Martensitic Transformation ◽  
Volume Fraction ◽  
Micromechanical Model ◽  
Slip Rate ◽  
Transformation Strain ◽  
Dislocation Motion ◽  
Lattice Spin ◽  
Two Phases ◽  
The One ◽  
Elastic Plastic Materials

During the martensitic transformation in elastic-plastic materials, the local transformation strain as well as the plastic flow inside austenite are strongly related with the crystallographic orientation of the austenitic lattice. Two mechanisms involved in these materials, i.e., plasticity by dislocation motion and martensitic phase formation are coupled through kinematical constraints so that the lattice spin of the austenitic grains is different from the one due to classical slip. In this work, the lattice spin ω˙eA of the austenitic grains is related with the slip rate on the slip systems of the two phases, γ˙A and γ˙M, the evolution of the martensite volume fraction f˙ and the overall rotation rate Ω˙ of the grains. This new relation is integrated in a micromechanical model developed for unstable austenite in order to predict the evolution of the austenite texture during TRansformation Induced Plasticity (TRIP). Results for the evolution of the lattice orientation during martensitic transformation are compared with experimental data obtained by X-ray diffraction on a 304 AISI steel.

On the Dynamic Growth of a Spherical Inclusion With Dilatational Transformation Strain in Infinite Elastic Domain

1999 ◽  
Vol 66 (4) ◽  
pp. 879-884 ◽  
Author(s):  
B. Wang ◽  
Q. Sun ◽  
Z. Xiao
Keyword(s):  
Hydrostatic Stress ◽  
Spherical Inclusion ◽  
Reduction Rate ◽  
Dynamic Effect ◽  
Propagation Speed ◽  
Transformation Strain ◽  
Elastic Fields ◽  
Initiation And Propagation ◽  
Dynamic Growth ◽  
Basic Ideas

In this paper, the dynamic effect was incorporated into the initiation and propagation process of a transformation inclusion. Based on the time-varying propagation equation of a spherical transformation inclusion with pure dilatational eigenstrain, the dynamic elastic fields both inside and outside the inclusion were derived explicitly, and it is found that when the transformation region expands at a constant speed, the strain field inside the inclusion is time-independent and uniform for uniform eigenstrain. Following the basic ideas of crack propagation problems in dynamic fracture mechanics, the reduction rate of the mechanical part of the free energy accompanying the growth of the transformation inclusion was derived as the driving force for the move of the interface. Then the equation to determine the propagation speed was established. It is found that there exists a steady speed for the growth of the transformation inclusion when time is approaching infinity. Finally the relation between the steady speed and the applied hydrostatic stress was derived explicitly.

Development of Generalized Plane-Strain Tensors for the Concentric Cylinder

1995 ◽  
Vol 62 (3) ◽  
pp. 590-594
Author(s):  
N. Chandra ◽  
Zhiyum Xie
Keyword(s):  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Transformation Strain ◽  
Inclusion Problem ◽  
Infinite Domain ◽  
Concentric Cylinder ◽  
Finite Radius ◽  
Fiber Volume ◽  
Thermal Residual Stresses ◽  
The Matrix

A pair of two new tensors called GPS tensors S and D is proposed for the concentric cylindrical inclusion problem. GPS tensor S relates the strain in the inclusion constrained by the matrix of finite radius to the uniform transformation strain (eigenstrain), whereas tensor D relates the strain in the matrix to the same eigenstrain. When the cylindrical matrix is of infinite radius, tensor S reduces to the appropriate Eshelby’s tensor. Explicit expressions to evaluate thermal residual stresses σr, σθ and σz in the matrix and the fiber using tensor D and tensor S, respectively, are developed. Since the geometry of the present problem is of finite radius, the effect of fiber volume fraction on the stress distribution can be easily studied. Results for the thermal residual stress distributions are compared with Eshelby’s infinite domain solution and finite element results for a specified fiber volume fraction.

Transformation - strain relationships in trip steels

1974 ◽  
Vol 8 (5) ◽  
pp. 445-450 ◽  
Author(s):  
B.L. Jones ◽  
P.N. Jones
Keyword(s):  
Transformation Strain ◽  
Trip Steels
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