Thermodynamics Of Martensitic Transformation Research Articles

Influence of a Tensile Stress on the Thermodynamics of Martensitic Transformations: Frictional Work and Stored Elastic Energy Calculations in Polycrystalline Alloys

Influence of a Tensile Stress on the Thermodynamics of Martensitic Transformations: Frictional Work and Stored Elastic Energy Calculations in Polycrystalline Alloys

Thermoelastic Behaviour, Hysteresis, and Dissipative Forces in Thermodynamics of Martensitic Transformations

Thermoelastic Behaviour, Hysteresis, and Dissipative Forces in Thermodynamics of Martensitic Transformations

Thermodynamic and Kinetic Calculation of Non-Equilibrium Microstructure Design of TRIP Steel

The non-equilibrium microstructure of Fe-C-Mn-Si TRIP steel is designed bythermodynamic and kinetic calculation. The upper limit of bainitic transformation temperature iscalculated and compared to that characterized by CCT curve determination. s M temperature isdetermined based on thermodynamics of martensitic transformation and sublattice model. Thecalculation is conducted via TQ6-patch in Thermo-Calc software. Comparison between thecalculations and experiments reveals the relationship between non-equilibrium phase compositionand heat treatment parameters which can be utilized to achieve the elaborate design of alloy and heattreatment for super TRIP steel.

Investigation on the martensitic transformation in γ-Fe(n) nanoparticles

gamma-Fe(5.90-10.9 at. % N) nanoparticles ranging in diameters from 30 to 100 nm were prepared by laser-induced pyrolysis of mixtures of Fe(CO)(5) and NH3. During the quenching from high temperature to room temperature and even down to 4.2 K, no martensitic transformation occurred in these particles. Based on the effects of surface tension and refinement of grain size on the yield strength of the nanoparticles, the dependencies of nucleation driving force and the martensite-start temperature on the particle size was revealed, from a viewpoint of thermodynamics of martensitic transformation in the gamma-Fe(N) nanoparticles. It is suggested that the yield strength increment due to the surface tension and to the very fine crystallite grains is probably the predominant aspect responsible for inhibiting the nucleation of martensite and drastic decrease of the martensite-start temperature of the nanoparticles. High pressure of 0.5 - 4.0 GPa were adopted to induce the martensitic transition of the gamma-Fe nanoparticles. It is found that the extent of martensitic transformation increased with the increasing pressures, most individual gamma-Fe particles were partially transformed to martensite after pressurization.

Thermodynamics of the iron martensitic transformation and the ms temperature of iron

Based on the methodology put forward by Hsu on the thermodynamics of martensitic transformations of iron-carbon alloys, some aspects of thermodynamics of the iron martensitic transformation have been investigated by employing relatively reasonable experimental data. The Ms temperature of iron is 700 °C, as obtained in this paper. This is in good agreement with major experimental data in the literature. The driving force for the iron martensitic transformation is 438 J/mol, and the yield point of γ-iron at its Ms temperature is 46.3 MPa. Results presented in this paper can play as a modification to Hsu’s methodology.

Differential relations of the nonlocal nonequilibrium thermodynamics of martensitic transformations

Differential relations describing the change in the degree of martensitic transformation with change in the external temperature and pressure are derived. As an illustration, the relations are applied to the analysis of the experimental situation of apparent violation of the Clausing-Clapeyron equation.

The thermodynamics of martensitic transformation

The thermodynamic approach to the understanding of martensitic transformations can provide insight into the mechanism of transformation, serve as a generalization technique among the alloying systems, and as a framework for the synthesis of data on kinetic, structural, crystallographic, and other aspects of the transformation. The quality and utility of existing thermochemical models and data are examined. The approach requires long, unverifiable extrapolation of the thermodynamic functions and must be used with circumspection. On the other hand, much that is known is derived from a thermodynamic viewpoint. The present authors are not hopeful of great breakthroughs in the quality of the thermodynamic data. More significant, it appears, would be attempts to formally cast the areas of crystallographic analysis (transformation strain energy) and the like into the thermodynamic framework.