J. Vanaja - Academia.edu (original) (raw)
Papers by J. Vanaja
Metallurgical and Materials Transactions A
Journal of Nuclear Materials
Journal of Nuclear Materials
Materials Today Communications
Materials Science and Engineering: A
Transactions of the Indian National Academy of Engineering
Lecture Notes in Mechanical Engineering, 2019
In the present study, reduced activation ferritic–martensitic steel subjected to thermomechanical... more In the present study, reduced activation ferritic–martensitic steel subjected to thermomechanical treatment (TMT), in austenitic phase field and ferritic phase field, was evaluated for tensile properties (at temperatures 300–923 K) and compared with those under normalized and tempered (N+T) condition. The steel subjected to TMT in austenitic phase field consists of fully tempered martensitic structure and that subjected to TMT in ferritic phase field consists of the fully ferritic structure within prior austenite grain boundaries (PAGBs) after tempering treatment. In the case of TMT in austenitic phase field, allotriomorphic ferrite was also observed along the PAGBs of steel. The tempered martensite of TMT steels is decorated with the increased population of finer precipitates of M23C6 and MX-type compared to the N+T condition. The TMT process improved the strength properties of the steel over the N+T condition without compromising the ductility of the material. Interestingly, the s...
Materials at High Temperatures
ABSTRACT Creep deformation, damage and rupture behaviour of 304HCu austenitic stainless steel hav... more ABSTRACT Creep deformation, damage and rupture behaviour of 304HCu austenitic stainless steel have been studied at temperatures 923, 973 and 1023 K over the stress range 100–240 MPa. The material exhibited relatively short primary stage of creep deformation followed by secondary (steady-state creep) stage and relatively extensive tertiary stage of creep deformation. The transient creep deformation is analysed based on the Garofalo relationship, The variations of (i) rate of exhaustion of transient creep creep rate and time to onset of secondary creep and (ii) initial creep rate with were found to obey power-law relationship with powers close to unity, thereby facilitating the development of master transient creep curve. The variation of with stress and temperature obeyed Dorn’s equation modified with back stress concept. The time to onset of tertiary creep is found to be proportional to rupture life (tr) while the damage tolerance factor decreased with increase in tr. In view of the prolonged tertiary creep, associated with microstructural change and intergranular creep cavitation, Kachanov–Rabotnov model has been used to assess the creep damage behaviour of the steel. The damage assessment coupled with finite-element analysis closely predicted the creep deformation and rupture life of the steel.
Journal of Nuclear Materials, 2012
ABSTRACT Tensile strength and flow behaviour of a Reduced Activation Ferritic–Martensitic (RAFM) ... more ABSTRACT Tensile strength and flow behaviour of a Reduced Activation Ferritic–Martensitic (RAFM) steel (9Cr–1W–0.06Ta–0.22V–0.08C) have been investigated over a temperature range of 300–873 K at different strain rates. Tensile strength of the steel decreased with temperature and increased with strain rate except at intermediate temperatures. Negative strain rate sensitivity of flow stress of the steel at intermediate temperatures revealed the occurrence of dynamic strain ageing in the steel, even though no serrated flow was observed. The tensile flow behaviour of the material was well represented by the Voce strain hardening equation for all the test conditions. Temperature and strain rate dependence of the various parameters of Voce equation were interpreted with the possible deformation mechanisms. The equivalence between the saturation stress at a given strain rate in tensile test and steady state deformation rate at a given stress in creep test was found to be satisfied by the RAFM steel.
Journal of Nuclear Materials, 2011
Tensile and creep properties of a reduced activation ferriticmartensitic (RAFM) steel for Indian... more Tensile and creep properties of a reduced activation ferriticmartensitic (RAFM) steel for Indian Test Blanket Module (TBM) to be tested in ITER have been evaluated. The tensile strength was found to decrease with temperature; the rate of decrease being slower in the ...
Journal of Nuclear Materials, 2013
ABSTRACT Effect of tungsten in the range of 1–2 wt.% on tensile properties and flow behaviour of ... more ABSTRACT Effect of tungsten in the range of 1–2 wt.% on tensile properties and flow behaviour of 9Cr–W–Ta–V Reduced Activation Ferritic–Martensitic (RAFM) steel has been investigated. The tungsten in the investigated range was found to have only minor effect on the tensile properties of the steel over the temperature range of 300–873 K and at a strain rate of 3 × 10−3 s−1. The tensile flow behaviour of the RAFM steels was adequately described by the Voce’s constitutive equation. The tensile strength of the steels were predicted well from the parameters of the Voce’s constitutive equation. The Voce’s strain hardening parameter ‘nv’ was found to be quite sensitive to the tungsten content and predicted the onset of dislocation climbing process at relatively higher testing temperature with the increase in tungsten content. The equivalence between tensile and creep deformations and the influence of tungsten have been discussed.
Materials Science and Engineering: A, 2012
This paper presents the creep deformation and rupture behaviour of indigenously produced 9Cr-1W-0... more This paper presents the creep deformation and rupture behaviour of indigenously produced 9Cr-1W-0.2V-0.06Ta Reduced Activation Ferritic-Martensitic (RAFM) steel for fusion reactor application. Creep studies were carried out at 773, 823 and 873K over a stress range of 100–300MPa. The creep deformation of the steel was found to proceed with relatively shorter primary regime followed by an extended tertiary regime with
International Journal of Pressure Vessels and Piping
IOP Conference Series: Materials Science and Engineering
The present study focuses on the evaluation of microstructure and mechanical properties of reduce... more The present study focuses on the evaluation of microstructure and mechanical properties of reduced activation ferritic-martensitic (RAFM) steel (9Cr-1W-0.06Ta) subjected to thermo-mechanical treatment (TMT) in ferritic phase field. The results obtained were compared with the steel in conventional normalised plus tempered (N+T) condition. The microstructure of the steel in N+T and TMT conditions was assessed by optical and scanning electron microscopes. Hardness, tensile and creep studies were carried out and the results were correlated with the microstructural studies. While the TMT processed steel resulted in coarser prior austenite grains and exhibited ferritic microstructure with large distribution of fine M 23 C 6 and MX precipitates, the N+T steel reveals tempered martensitic structure with finer prior austenitic grains with coarser M 23 C 6 and MX precipitates. Although ferritic structure is present in TMT processed steel, it exhibits better tensile and creep rupture strengths than N+T steel due to the presence of increased dislocation density and finer distribution of precipitates.
Journal of Nuclear Materials
Journal of Nuclear Materials
Materials Science and Engineering: A
Materials Science and Engineering: A
Materials Science and Engineering: A
Metallurgical and Materials Transactions A
Journal of Nuclear Materials
Journal of Nuclear Materials
Materials Today Communications
Materials Science and Engineering: A
Transactions of the Indian National Academy of Engineering
Lecture Notes in Mechanical Engineering, 2019
In the present study, reduced activation ferritic–martensitic steel subjected to thermomechanical... more In the present study, reduced activation ferritic–martensitic steel subjected to thermomechanical treatment (TMT), in austenitic phase field and ferritic phase field, was evaluated for tensile properties (at temperatures 300–923 K) and compared with those under normalized and tempered (N+T) condition. The steel subjected to TMT in austenitic phase field consists of fully tempered martensitic structure and that subjected to TMT in ferritic phase field consists of the fully ferritic structure within prior austenite grain boundaries (PAGBs) after tempering treatment. In the case of TMT in austenitic phase field, allotriomorphic ferrite was also observed along the PAGBs of steel. The tempered martensite of TMT steels is decorated with the increased population of finer precipitates of M23C6 and MX-type compared to the N+T condition. The TMT process improved the strength properties of the steel over the N+T condition without compromising the ductility of the material. Interestingly, the s...
Materials at High Temperatures
ABSTRACT Creep deformation, damage and rupture behaviour of 304HCu austenitic stainless steel hav... more ABSTRACT Creep deformation, damage and rupture behaviour of 304HCu austenitic stainless steel have been studied at temperatures 923, 973 and 1023 K over the stress range 100–240 MPa. The material exhibited relatively short primary stage of creep deformation followed by secondary (steady-state creep) stage and relatively extensive tertiary stage of creep deformation. The transient creep deformation is analysed based on the Garofalo relationship, The variations of (i) rate of exhaustion of transient creep creep rate and time to onset of secondary creep and (ii) initial creep rate with were found to obey power-law relationship with powers close to unity, thereby facilitating the development of master transient creep curve. The variation of with stress and temperature obeyed Dorn’s equation modified with back stress concept. The time to onset of tertiary creep is found to be proportional to rupture life (tr) while the damage tolerance factor decreased with increase in tr. In view of the prolonged tertiary creep, associated with microstructural change and intergranular creep cavitation, Kachanov–Rabotnov model has been used to assess the creep damage behaviour of the steel. The damage assessment coupled with finite-element analysis closely predicted the creep deformation and rupture life of the steel.
Journal of Nuclear Materials, 2012
ABSTRACT Tensile strength and flow behaviour of a Reduced Activation Ferritic–Martensitic (RAFM) ... more ABSTRACT Tensile strength and flow behaviour of a Reduced Activation Ferritic–Martensitic (RAFM) steel (9Cr–1W–0.06Ta–0.22V–0.08C) have been investigated over a temperature range of 300–873 K at different strain rates. Tensile strength of the steel decreased with temperature and increased with strain rate except at intermediate temperatures. Negative strain rate sensitivity of flow stress of the steel at intermediate temperatures revealed the occurrence of dynamic strain ageing in the steel, even though no serrated flow was observed. The tensile flow behaviour of the material was well represented by the Voce strain hardening equation for all the test conditions. Temperature and strain rate dependence of the various parameters of Voce equation were interpreted with the possible deformation mechanisms. The equivalence between the saturation stress at a given strain rate in tensile test and steady state deformation rate at a given stress in creep test was found to be satisfied by the RAFM steel.
Journal of Nuclear Materials, 2011
Tensile and creep properties of a reduced activation ferriticmartensitic (RAFM) steel for Indian... more Tensile and creep properties of a reduced activation ferriticmartensitic (RAFM) steel for Indian Test Blanket Module (TBM) to be tested in ITER have been evaluated. The tensile strength was found to decrease with temperature; the rate of decrease being slower in the ...
Journal of Nuclear Materials, 2013
ABSTRACT Effect of tungsten in the range of 1–2 wt.% on tensile properties and flow behaviour of ... more ABSTRACT Effect of tungsten in the range of 1–2 wt.% on tensile properties and flow behaviour of 9Cr–W–Ta–V Reduced Activation Ferritic–Martensitic (RAFM) steel has been investigated. The tungsten in the investigated range was found to have only minor effect on the tensile properties of the steel over the temperature range of 300–873 K and at a strain rate of 3 × 10−3 s−1. The tensile flow behaviour of the RAFM steels was adequately described by the Voce’s constitutive equation. The tensile strength of the steels were predicted well from the parameters of the Voce’s constitutive equation. The Voce’s strain hardening parameter ‘nv’ was found to be quite sensitive to the tungsten content and predicted the onset of dislocation climbing process at relatively higher testing temperature with the increase in tungsten content. The equivalence between tensile and creep deformations and the influence of tungsten have been discussed.
Materials Science and Engineering: A, 2012
This paper presents the creep deformation and rupture behaviour of indigenously produced 9Cr-1W-0... more This paper presents the creep deformation and rupture behaviour of indigenously produced 9Cr-1W-0.2V-0.06Ta Reduced Activation Ferritic-Martensitic (RAFM) steel for fusion reactor application. Creep studies were carried out at 773, 823 and 873K over a stress range of 100–300MPa. The creep deformation of the steel was found to proceed with relatively shorter primary regime followed by an extended tertiary regime with
International Journal of Pressure Vessels and Piping
IOP Conference Series: Materials Science and Engineering
The present study focuses on the evaluation of microstructure and mechanical properties of reduce... more The present study focuses on the evaluation of microstructure and mechanical properties of reduced activation ferritic-martensitic (RAFM) steel (9Cr-1W-0.06Ta) subjected to thermo-mechanical treatment (TMT) in ferritic phase field. The results obtained were compared with the steel in conventional normalised plus tempered (N+T) condition. The microstructure of the steel in N+T and TMT conditions was assessed by optical and scanning electron microscopes. Hardness, tensile and creep studies were carried out and the results were correlated with the microstructural studies. While the TMT processed steel resulted in coarser prior austenite grains and exhibited ferritic microstructure with large distribution of fine M 23 C 6 and MX precipitates, the N+T steel reveals tempered martensitic structure with finer prior austenitic grains with coarser M 23 C 6 and MX precipitates. Although ferritic structure is present in TMT processed steel, it exhibits better tensile and creep rupture strengths than N+T steel due to the presence of increased dislocation density and finer distribution of precipitates.
Journal of Nuclear Materials
Journal of Nuclear Materials
Materials Science and Engineering: A
Materials Science and Engineering: A
Materials Science and Engineering: A