Indrajit Charit

Profile Information
Name
Indrajit Charit
Institution
University of Idaho
Position
Associate Professor
Affiliation
University of Idaho
h-Index
ORCID
0000-0002-3854-2900
Expertise
Friction Stir Welding, Mechanical Properties, Metallurgy, Nanocrystalline, Spark Plasma Sintering
Publications:
"A Preliminary Investigation of High Dose Ion Irradiation Response of a Lanthana-Bearing Nanostructured Ferritic Steel Processed via Spark Plasma Sintering" Somayeh Pasebani, Indrajit Charit, Ankan Guria, Yaqiao Wu, Jatuporn Burns, Darryl Butt, James Cole, Lin Shao, Journal of Nuclear Materials Vol. 495 2017 78-84 Link
A lanthana-containing nanostructured ferritic steel (NFS) was processed via mechanical alloying (MA) of Fe-14Cr-1Ti-0.3Mo-0.5La2O3 (wt.%) and consolidated via spark plasma sintering (SPS). In order to study the consolidation behavior via SPS, sintering temperature and dwell time were correlated with microstructure, density, microhardness and shear yield strength of the sintered specimens. A bimodal grain size distribution including both micron-sized and nano-sized grains was observed in the microstructure of specimens sintered at 850, 950 and 1050 oC for 45 min. Significant densification occurred at temperatures greater than 950 oC with a relative density higher than 98%. A variety of nanoparticles, some enriched in Fe and Cr oxides and copious nanoparticles smaller than 10 nm with faceted morphology and enriched in La and Ti oxides were observed. After SPS at 950 oC, the number density of Cr-Ti-La-O enriched nanoclusters with an average radius of 1.5 nm was estimated to be 1.2 ×10^24 m^-3 . The La + Ti : O ratio was close to 1 after SPS at 950 and 1050 C; however, the number density of nanoclusters decreased at 1050 C. With SPS above 950 C, the density improved but the microhardness and shear yield strength decreased due to partial coarsening of the grains and nanoparticles.
"A preliminary study on the development of La2O3-bearing nanostructured ferritic steels via high energy ball milling" Somayeh Pasebani, Indrajit Charit, Darryl Butt, James Cole, Journal of Nuclear Materials Vol. 434 2013 282-286 Link
Elemental powder mixture of Fe–Cr–Ti–Mo and La2O3 were ball milled for different milling times in a high energy shaker mill. Effects of ball milling time on crystallite size, particle size and hardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester. After 10 h of ball milling, the smallest crystallite size and highest hardness were ~24 nm and ~970 HV, respectively. Transmission electron microscopy (TEM) studies have revealed nanoscale features 2–5 nm in diameter present in the milled powder. Local atom probe tomography studies have shown that these nanoscale features were possibly nanoclusters enriched in La, TiO and O.
"Effect of alloying elements on the microstructure and mechanical properties of nanostructured ferritic steels produced by spark plasma sintering" Indrajit Charit, Somayeh Pasebani, Journal of Alloys and Compounds Vol. 599 2014 206-211 Link
Several Fe–14Cr based alloys with varying compositions were processed using a combined route of mechanical alloying and spark plasma sintering. Microstructural characteristics of the consolidated alloys were examined via transmission electron microscopy and atom probe tomography, and mechanical properties evaluated using microhardness testing. Lanthanum oxide (0.5 wt.%) was added to Fe–14Cr leading to improvement in microstructural stability and mechanical properties mainly due to a high number density of La–Cr–O-enriched nanoclusters. The combined addition of La, Ti (1 wt.%) and Mo (0.3 wt.%) to the Fe–14Cr base composition further enhanced the microstructural stability and mechanical properties. Nanoclusters enriched in Cr–Ti–La–O with a number density of 1.4 × 1024 m-3 were found in this alloy with a bimodal grain size distribution. After adding Y2O3 (0.3 wt.%) along with Ti and Mo to the Fe–14Cr matrix, a high number density (1.5 × 1024 m-3) of Cr–Ti–Y–O-enriched NCs was also detected. Formation mechanism of these nanoclusters can be explained through the concentrations and diffusion rates of the initial oxide species formed during the milling process and initial stages of sintering as well as the thermodynamic nucleation barrier and their enthalpy of formation.
"Effect of alloying elements on the microstructure and mechanical properties of nanostructured ferritic steels produced by spark plasma sintering" Somayeh Pasebani, Indrajit Charit, Journal of Alloys and Compounds Vol. 599 2014 206-214 Link
"High Temperature Tensile Properties and Related Microstructural Evolution in Grade 92 Steel" SULTAN ALSAGABI, Indrajit Charit, Somayeh Pasebani, Mechanical and Creep Behavior of Advanced Materials, Part of the Minerals, Metals & Materials Series (MMMS) Vol. 2017 229-242 Link
Ferritic-martensitic steels with good high temperature mechanical properties have many promising applications in fossil and nuclear power plants. In this work, a F92 steel was tensile tested from room to elevated temperatures (up to 700 °C). This material exhibited higher strength than traditional P92 steels. The reasons for the observed changes in mechanical properties were investigated by studying the microstructural characteristics in undeformed and deformed specimens using transmission electron microscopy. The microstructural evolution accelerated significantly under loading as temperature increased. For instance, the deformed microstructure at 600 °C showed early stages of M23C6 precipitate formation under loading. The M23C6 precipitates exhibited more coarsening tendency whereas the MX-type precipitates retained their size. As coarsening of M23C6 precipitates progressed at elevated temperatures, the strength gradually decreased as the solid solution strengthening deteriorated by removing W and Mo from the solid solution matrix.
"Lanthana-bearing nanostructured ferritic steels via spark plasma sintering" SULTAN ALSAGABI, Darryl Butt, Indrajit Charit, James Cole, Somayeh Pasebani, Yaqiao Wu, Jatuporn Burns, Kerry Allahar, Journal of Nuclear Materials Vol. 470 2016 297-306 Link
A lanthana-containing nanostructured ferritic steel (NFS) was processed via mechanical alloying (MA) of Fe-14Cr-1Ti-0.3Mo-0.5La2O3 (wt.%) and consolidated via spark plasma sintering (SPS). In order to study the consolidation behavior via SPS, sintering temperature and dwell time were correlated with microstructure, density, microhardness and shear yield strength of the sintered specimens. A bimodal grain size distribution including both micron-sized and nano-sized grains was observed in the microstructure of specimens sintered at 850, 950 and1050 °C for 45 min. Significant densification occurred at temperatures greater than 950 °C with a relative density higher than 98%. A variety of nanoparticles, some enriched in Fe and Cr oxides and copious nanoparticles smaller than 10 nm with faceted morphology and enriched in La and Ti oxides were observed. After SPS at 950 °C, the number density of Cr–Ti–La–O-enriched nanoclusters with an average radius of 1.5 nm was estimated to be 1.2 × 1024 m−3. The La + Ti:O ratio was close to 1 after SPS at 950 and 1050 °C; however, the number density of nanoclusters decreased at 1050 °C. With SPS above 950 °C, the density improved but the microhardness and shear yield strength decreased due to partial coarsening of the grains and nanoparticles.
"Mechanical Alloying of Lanthana-Bearing Nanostructured Ferritic Steels" Darryl Butt, James Cole, Somayeh Pasebani, Yaqiao Wu, Indrajit Charit, Acta Materialia Vol. 61 2013 5605-5617 Link
A novel nanostructured ferritic steel powder with the nominal composition Fe–14Cr–1Ti–0.3Mo–0.5La2O3 (wt.%) was developed via high energy ball milling. La2O3 was added to this alloy instead of the traditionally used Y2O3. The effects of varying the ball milling parameters, such as milling time, steel ball size and ball to powder ratio, on the mechanical properties and microstructural characteristics of the as-milled powder were investigated. Nanocrystallites of a body-centered cubic ferritic solid solution matrix with a mean size of approximately 20 nm were observed by transmission electron microscopy. Nanoscale characterization of the as-milled powder by local electrode atom probe tomography revealed the formation of Cr–Ti–La–O-enriched nanoclusters during mechanical alloying. The Cr:Ti:La:O ratio is considered “non-stoichiometric”. The average size (radius) of the nanoclusters was about 1 nm, with number density of 3.7x10^24 m^-3. The mechanism for formation of nanoclusters in the as-milled powder is discussed. La2O3 appears to be a promising alternative rare earth oxide for future nanostructured ferritic steels.
"Microstructural stability of a self-ion irradiated lanthana-bearing nanostructured ferritic steel" SULTAN ALSAGABI, Darryl Butt, Indrajit Charit, James Cole, Somayeh Pasebani, Lin Shao, Jatuporn Burns, Lloyd Price, Journal of Nuclear Materials Vol. 462 2015 191-204 Link
Thermally stable nanofeatures with high number density are expected to impart excellent high temperature strength and irradiation stability in nanostructured ferritic steels (NFSs) which have potential applications in advanced nuclear reactors. A lanthana-bearing NFS (14LMT) developed via mechanical alloying and spark plasma sintering was used in this study. The sintered samples were irradiated by Fe2+ ions to 10, 50 and 100 dpa at 30 °C and 500 °C. Microstructural and mechanical characteristics of the irradiated samples were studied using different microscopy techniques and nanoindentation, respectively. Overall morphology and number density of the nanofeatures remained unchanged after irradiation. Average radius of nanofeatures in the irradiated sample (100 dpa at 500 °C) was slightly reduced. A notable level of irradiation hardening and enhanced dislocation activity occurred after ion irradiation except at 30 °C and ⩾50 dpa. Other microstructural features like grain boundaries and high density of dislocations also provided defect sinks to assist in defect removal.
"Processing of a novel nanostructured ferritic steel via spark plasma sintering and investigation of its mechanical and microstructural characteristics" Darryl Butt, Indrajit Charit, James Cole, Somayeh Pasebani, Yaqiao Wu, Jatuporn Burns, Kerry Allahar, INIS Repository Vol. 46 2015 Link
Nano-structured ferritic steels (NFSs) with 12-14 wt% Cr have attracted widespread interest for potential high temperature structural and fuel cladding applications in advanced nuclear reactors. They have excellent high temperature mechanical properties and high resistance to radiation-induced damage. The properties of the NFSs depend on the composition that mainly consists of Cr, Ti, W or Mo, and Y2O3 as alloying constituents. In this study, a novel nano-structured ferritic steel (Fe-14Cr-1Ti-0.3Mo-0.5La2O3, wt%) termed as 14LMT was developed via high energy ball milling and spark plasma sintering. Vickers microhardness values were measured. Microstructural studies of the developed NFSs were performed by EBSD and TEM, which revealed a bimodal grain size distribution. A significant number density of nano-precipitates was observed in the microstructure. The diameter of the precipitates varied between 2-70 nm and the morphology from the spherical to faceted shape. The Cr-La-Ti-O-enriched nano-clusters were identified by APT studies.
"Sintering Behavior of Lanthana-Bearing Nanostructured Ferritic Steel Consolidated via Spark Plasma Sintering" Darryl Butt, Indrajit Charit, James Cole, Somayeh Pasebani, Yaqiao Wu, Jatuporn Burns, Advanced Engineering Materials Vol. 18 2015 324-332 Link
Elemental powder mixture of Fe–14Cr–1Ti–0.3Mo–0.5La2O3(wt%) composition is mechanicallyalloyed for different milling durations (5, 10 and 20 h) and subsequently consolidated via spark plasmasintering under vacuum at 950?C for 7 min. The effects of milling time on the densi?cation behaviorand density/microhardness are studied. The sintering activation energy is found to be close to that ofgrain boundary diffusion. The bimodal grain structure created in the milled and sintered material isfound to be a result of milling and not of sintering alone. The oxide particle diameter varies between2 and 70 nm. Faceted precipitates smaller than 10 nm in diameter are found to be mostly La–Ti–Cr-enriched complex oxides that restrict further recrystallization and related phenomena
"The Irradiation Performance and Microstructural Evolution in 9Cr-2W Steel Under Ion Irradiation" SULTAN ALSAGABI, Indrajit Charit, Somayeh Pasebani, Journal of Materials Engineering and Performance Vol. 25 2016 401-408 Link
Grade 92 steel (9Cr-2W) is a ferritic-martensitic steel with good mechanical and thermal properties. It is being considered for structural applications in Generation IV reactors. Still, the irradiation performance of this alloy needs more investigation as a result of the limited available data. The irradiation performance investigation of Grade 92 steel would contribute to the understanding of engineering aspects including feasibility of application, economy, and maintenance. In this study, Grade 92 steel was irradiated by iron ion beam to 10, 50, and 100 dpa at 30 and 500 °C. In general, the samples exhibited good radiation damage resistance at these testing parameters. The radiation-induced hardening was higher at 30 °C with higher dislocation density; however, the dislocation density was less pronounced at higher temperature. Moreover, the irradiated samples at 30 °C had defect clusters and their density increased at higher doses. On the other hand, dislocation loops were found in the irradiated sample at 50 dpa and 500 °C. Further, the irradiated samples did not show any bubble or void.
Presentations:
"Development of Nanostructured Ferritic Alloys Containing Lanthana-based Nanoparticles via Spark Plasma Sintering" Darryl Butt, Indrajit Charit, James Cole, TMS 2014 February 16-20, (2014)
"Processing of a Novel Nanostructured Ferritic Steel via Spark Plasma Sintering and Investigation of Its Mechanical and Microstructural Characteristics" Darryl Butt, Indrajit Charit, James Cole, Somayeh Pasebani, Yaqiao Wu, SMINS-3 October 7-10, (2013)