scholarly journals Structural Features and Operational Characteristics of Steel T91

2020 ◽  
Keyword(s):  
Grain Size ◽  
Deformation Temperature ◽  
Structural Features ◽  
Uniform Structure ◽  
High Dose ◽  
Initial State ◽  
Operational Characteristics ◽  
Average Grain Size ◽  
Temperature Ranges ◽  
Number Of Cycles

The microstructure and radiation resistance of T91 martensitic steel were studied after thermomechanical treatment. The physical and technological foundations of the process of creating of a nanostructured state in T91 reactor steel have been developed. This structure was received by severe plastic deformation of T91 steel by the multiple “upsetting-extrusion” method (developed at the NSC KIPT) in two temperature ranges of deformation: in the region of austenite existing and with a successive decrease in the deformation temperature and an increase in cycles of “upsetting-extrusion” in the field of ferrite existence. For the further heat treatment the particular temperature range and deformation modes were chosen to obtain optimal structure. Also, the optimum temperature of tempering to receive the uniform structure was established. It was found that the average grain size of T91 steel decreases from 20 μm in the initial state to ~ 140 nm after 5 cycles of “upsetting-extrusion” in the ferrite interval and to ~ 100 nm after 3 cycles of deformation in the austenitic region. It was determined that with an increase in the number of cycles and a decrease in the deformation temperature, a rise in the degree of uniformity of grain size distribution occurs. In this case, the microhardness increases from 2090 MPa to 2850 MPa after 5 cycles of “upsetting-extrusion” in the ferritic interval. In the austenitic region, the microhardness values increase from 3400 to 3876 MPa. The swelling of T91 steel in two structural states, martensitic and ferritic, was determined. Thus, steel swelling at a high dose of irradiation with argon ions with an energy of 1.4 MeV (120 displacements per atom, irradiation temperature 460 ° C) is ΔV / V = 0.26% in the initial state (martensitic structure) and 0.65% for samples with a ferritic structure.

scholarly journals Structural Transformations and Mechanical Properties of Metastable Austenitic Steel under High Temperature Thermomechanical Treatment

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 645
Author(s):  
Igor Litovchenko ◽  
Sergey Akkuzin ◽  
Nadezhda Polekhina ◽  
Kseniya Almaeva ◽  
Evgeny Moskvichev
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Temperature ◽  
Austenitic Steel ◽  
Structural Transformations ◽  
Initial State ◽  
Twin Boundaries ◽  
Metastable Austenitic Steel ◽  
Average Grain Size ◽  
Heating Up

The effect of high-temperature thermomechanical treatment on the structural transformations and mechanical properties of metastable austenitic steel of the AISI 321 type is investigated. The features of the grain and defect microstructure of steel were studied by scanning electron microscopy with electron back-scatter diffraction (SEM EBSD) and transmission electron microscopy (TEM). It is shown that in the initial state after solution treatment the average grain size is 18 μm. A high (≈50%) fraction of twin boundaries (annealing twins) was found. In the course of hot (with heating up to 1100 °C) plastic deformation by rolling to moderate strain (e = 1.6, where e is true strain) the grain structure undergoes fragmentation, which gives rise to grain refining (the average grain size is 8 μm). Partial recovery and recrystallization also occur. The fraction of low-angle misorientation boundaries increases up to ≈46%, and that of twin boundaries decreases to ≈25%, compared to the initial state. The yield strength after this treatment reaches up to 477 MPa with elongation-to-failure of 26%. The combination of plastic deformation with heating up to 1100 °C (e = 0.8) and subsequent deformation with heating up to 600 °C (e = 0.7) reduces the average grain size to 1.4 μm and forms submicrocrystalline fragments. The fraction of low-angle misorientation boundaries is ≈60%, and that of twin boundaries is ≈3%. The structural states formed after this treatment provide an increase in the strength properties of steel (yield strength reaches up to 677 MPa) with ductility values of 12%. The mechanisms of plastic deformation and strengthening of metastable austenitic steel under the above high-temperature thermomechanical treatments are discussed.

Effect of high-power ion beams on the surface topography and structure of submicrocrystalline titanium alloy subsurface layers

2018 ◽  
pp. 82-91
Author(s):  
M. V. Zhidkov ◽  
A. E. Ligachev ◽  
Yu. R. Kolobov ◽  
G. V. Potemkin ◽  
G. E. Remnev
Keyword(s):  
Grain Size ◽  
Titanium Alloy ◽  
High Power ◽  
Ion Beam ◽  
Structural Phase ◽  
Subsurface Layer ◽  
Ion Beams ◽  
Uniform Structure ◽  
Average Grain Size ◽  
Subsurface Layers

The study covers the topography and structural phase state of VT1-0 and VT6 submicrocrystalline titanium alloy subsurface layers irradiated by high power pulsed carbon ion beams (ion energy is 250 keV, pulse duration is ~100 ns, pulse current density is 150–200 A/cm2; surface energy density of a single pulse is j ~ 3 J/cm2 when irradiating VT1-0 titanium alloy samples and j ~ 1 J/cm2 when processing VT6 titanium alloy samples; pulse number is 1, 5, 10, and 50). The surface of samples was subjected to preliminary mechanical grinding and polishing before irradiation. It was shown that surface defects are formed on the surface of the alloys after irradiation, namely craters of different shapes and geometries with a diameter from fractions of a micron to 80–100 μm. At the same time, the grain structure in the subsurface layer becomes more homogeneous in terms of grain size and equiaxial properties. The initial state of titanium alloys is characterized by a fairly homogeneous structure with an average grain size of ~0,31 μm for VT1-0 and ~0,9 μm for VT6. After one irradiation pulse, grain growth to 0,54 μm in the transverse direction is observed in the subsurface layer of the VT1-0 alloy (j ~ 3 J/cm2), while grain size decreases to ~ 0,54 μm in the VT6 alloy (j ~ 1 J/cm2). After 50 pulses, the average grain size in the subsurface layer reaches ~2,2 μm for the VT1-0 alloy and ~1,6 μm for VT6. It should be noted that a rather uniform structure with equiaxed grains is formed as early as after treating with 1 high power ion beam pulse.

scholarly journals The Microstructure Evolution of Thermal Deformation of Continuous Extrusion Copper Bus Bar

2018 ◽  
Vol 228 ◽  
pp. 04006
Author(s):  
Jing Lu ◽  
Gaosheng Fu ◽  
Zhimeng Ren ◽  
Jie Liu ◽  
Huan Hao
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Deformation Temperature ◽  
Thermal Deformation ◽  
Raw Material ◽  
Test Machine ◽  
Deformation Microstructure ◽  
Average Grain Size ◽  
Continuous Extrusion

The thermal deformation microstructure of continuous extrusion copper bus bar was observed and analyzed in the temperature range from 200°C to 700°C and at strain rate from 0.01s-1 to 10.0s-1 and at deformation amount from30% to 90% on Gleeble1500 test machine. The experiment results show that the higher the temperature, the lower the strain rate, the more dynamic recrystallization occurred. At the same strain rate, the copper bus bar changes from raw material of as-cast organization to recrystallization grain gradually as the deformation temperature and deformation degree increase, and the recrystallization grain size grows older with the rise of temperature. At the same deformation temperature, the temperature of recrystallization nucleation decreases while the strain rate increases. At low strain rate (0.01~1.0s-1), the dynamic recrystallization occurred at 500°C. While at high strain rate (10.0s-1), the recrystallization nucleation is advanced and it is already completed at 500°C. The Z parameters can be used to express the effect of deformation temperature and strain rate on the average grain size D, and the prediction model of the thermal deformation microstructure is obtained as follows: lnD=4.822-0.018lnZ

scholarly journals The Effect of ECAP Temperature on the Microstructure and Properties of a Rolled Rare Earth Magnesium Alloy

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1554 ◽  
Author(s):  
Yun Tan ◽  
Wei Li ◽  
Weiwei Hu ◽  
Xiaofang Shi ◽  
Liang Tian
Keyword(s):  
Grain Size ◽  
Rare Earth ◽  
Magnesium Alloy ◽  
Deformation Temperature ◽  
Diffraction Intensity ◽  
Electron Backscattered Diffraction ◽  
Angular Pressing ◽  
Average Grain Size ◽  
Different Temperatures ◽  
Microstructure Examination

Deformation of an as-rolled rare earth Mg-2Y-0.6Nd-0.6Zr alloy, at different temperatures, was carried out along the BC (90° anticlockwise rotation of the samples after each ECAP pass) route by equal channel angular pressing (ECAP). The effects of the deformation temperature and the predeformation on the microstructure of the magnesium alloy were determined by the microstructure examination. The slip systems and texture change of the Mg-2Y-0.6Nd-0.6Zr alloy were investigated by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD), after equal channel angular deformation. The results showed that after seven passes of rolling, the grain size in the Mg-2Y-0.6Nd-0.6Zr alloy was refined to approximately 22 µm and the slip occurred mainly by a cylindrical slip and a pyramidal slip. After one pass of ECAP at 340 °C, the internal average grain size was significantly reduced to 11 µm, the cylindrical diffraction intensity clearly weakened, and the pyramidal diffraction intensity increased. EBSD pole figure analysis revealed that the base texture of the rolled Mg-2Y-0.6Nd-0.6Zr alloy weakened from 24.31 to 11.34 after ECAP. The mechanical properties indicated that the tensile strength and elongation of the rolled Mg-2Y-0.6Nd-0.6Zr alloy reached maximum values, when the deformation temperature was 340 °C.

Effect of Compression with Oscillatory Torsion Processing on Structure and Properties of Cu

2011 ◽  
Vol 674 ◽  
pp. 129-134 ◽  
Author(s):  
Kinga Rodak ◽  
Jacek Pawlicki ◽  
Krzysztof Radwański ◽  
Rafal M. Molak
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Grain Size ◽  
Subgrain Size ◽  
Strength Properties ◽  
Image Correlation ◽  
Compression Rate ◽  
Initial State ◽  
Electron Backscattered Diffraction ◽  
Average Grain Size

In this study, commercial Cu was subjected to plastic deformation by compression with oscillatory torsion. Different deformation parameters were adopted to study their effects on the microstructure and mechanical properties of Cu. The deformed microstructure was characterized by using scanning electron microscopy (SEM) equipment with electron backscattered diffraction (EBSD) facility and scanning transmission electron microscopy (STEM). The mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. Can be found, that process performed at high compression rate and high torsion frequency is recommended for the refining grain size. The size of structure elements: average grain size (D) and subgrain size (d) reached 0.42 m and 0.30 m respectively, and the fraction of high angle boundaries was 35%, when the sample was deformed at a torsion frequency f= 1.6 Hz and compression rate v=0.04 mm/s. Deformation at these parameters leads to an improvement in strength properties. The strength properties are about two times greater than the initial state.

Effect of Rolling Direction on the Microstructure and Mechanical Properties of Accumulative Roll Bonding (ARB) Processed Commercially Pure 1050 Aluminum Alloy

2006 ◽  
Vol 503-504 ◽  
pp. 681-686 ◽  
Author(s):  
Yong Suk Kim ◽  
Suk Ha Kang ◽  
Dong Hyuk Shin
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Tensile Elongation ◽  
Rolling Direction ◽  
Rolled Plate ◽  
Al Alloy ◽  
Cycle Number ◽  
Average Grain Size ◽  
Number Of Cycles ◽  
1050 Aluminum Alloy

The cross-ARB (C-ARB) process, which adopts cross rolling of the two stacked plates, has been performed up to seven cycles on a commercial purity 1050 aluminum alloy to obtain ultrafine grains with an average grain size of 0.7μm. Microstructural evolution of the C-ARB processed aluminum alloy was examined by a transmission electron microscopy as a function of process cycle number (accumulated plastic strain). Tensile property of the severely deformed Al alloy was also explored. Grain size of grains of the C-ARB processed alloy varied across thickness of the rolled plate. The size of grains at the top and bottom of the rolled plate converged to 0.65μm, while that of grains at the center of the plate increased with the number of ARB cycles. Tensile strength of the CARB processed 1050 Al alloy increased from 100MPa (as-received) to 160MPa. Tensile elongation varied with the number of cycles, but 15% of failure strain was measured from the 6-cycle C-ARB processed specimen. The variation of the elongation with the cycle number coincided exactly with the variation of grain size at the center of the processed plate.

scholarly journals Effect of Cyclic Close Die Forging on the Microstructure and Mechanical Properties of Ti–5Al–3Mo–1.5V Alloy

2021 ◽  
Vol 3 (1) ◽  
pp. 15
Author(s):  
Truong An Nguyen ◽  
Manh Hung Le ◽  
Manh Tien Nguyen ◽  
Quoc Viet Pham
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Stress ◽  
Superplastic Deformation ◽  
Superplastic Forming ◽  
Maximum Elongation ◽  
Die Forging ◽  
Microstructure And Mechanical Properties ◽  
Average Grain Size ◽  
Number Of Cycles

The goal of this work was to study the effects of cyclic close die forging on the microstructure and mechanical properties of Ti–5Al–3Mo–1.5V alloy, which was produced in Vietnam. The factors considered include the deformation temperature (Td), at 850 °C, 900 °C, and 950 °C, and the number of cycles performed while forging in closed die (n)— 3, 6, and 9 times. The responses measured were average grain diameter (dtb) and tensile stress (σb). The results indicate that the smallest average grain size of 1 μm could be obtained at Td = 900 °C, n = 9 times and the tensile stresses were enhanced. The experimental results we obtained also suggest that the microstructure of Ti–5Al–3Mo–1.5V alloy is accordant for superplastic deformation. The superplastic forming of this alloy can show maximum elongation of 1000% or more.

Effect of Texture on Tensile Properties of an ECAP-Processed MA2-1 Magnesium Alloy

2010 ◽  
Vol 160 ◽  
pp. 159-164 ◽  
Author(s):  
Vladimir Serebryany ◽  
T.M. Ivanova ◽  
T.I. Savyolova ◽  
Sergey V. Dobatkin
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Tensile Properties ◽  
Uniform Elongation ◽  
Tensile Elongation ◽  
Annealed Alloy ◽  
Initial State ◽  
Central Type ◽  
Average Grain Size ◽  
The One

Various equal channel angular pressing (ECAP) regimes by routes A and Bc were applied to a commercial MA2-1 (Mg-5wt.%Al-1wt.%Zn-0.4wt.%Mn) alloy for the development of texture which is different from the one of conventionally extruded and annealed alloy. In order to avoid the grain-size effect, the ECAP-processed alloy was annealed to coarsen the grains. The alloy texture before and after the ECAP was determined by the approximation of the X-ray measured pole figures with the canonical normal distributions of central type. The ECAP implementation results in the formation of ultra-fine grained structure of the alloy with an average grain size of 2.0-2.4 µm. The ECAP also drastically changes the initial axial texture characterized by a sharp basal component by splitting it into several more scattered orientations. The degree of the orientation scattering depends on the ECAP regime and route. The annealing of alloy after ECAP results in the grain size growth to the initial state of the extruded and annealed alloy. In addition to that the texture changes of the ECAP-processed alloy after annealing, unlike the structure changes, don’t result in texture of the initial state. The mechanical tensile properties of the annealed alloy substantially depend on the preceding ECAP routes. The yield strength of the annealed alloy decreases after all routes of ECAP. On the contrary, the uniform elongation compared with the one of the initial state of the alloy decreases after 4A route and increases after 4Bc route of ECAP. The effect of the texture and structure on the yield strength and tensile elongation of the alloy after ECAP and annealing was estimated using calculation of the generalized Schmid factors for specific preferred orientations of the active deformation systems and Hall-Petch relationship.

Microstructure modeling of a sintered Al–4Si–0.6Mg alloy extruded at semi-solid temperature ranges

2021 ◽  
pp. 095440892110424
Author(s):  
Abeyram M Nithin ◽  
M Joseph Davidson ◽  
Chilakalapalli Surya Prakash Rao
Keyword(s):  
Grain Size ◽  
Peak Strain ◽  
Microstructure Modeling ◽  
Regression Parameters ◽  
Average Grain Size ◽  
Temperature Ranges ◽  
Grain Growth Model ◽  
Semi Solid ◽  
Deform 2D ◽  
Solid Temperature

The microstructure evolution of sintered and extruded samples of Al–4Si–0.6Mg powder alloys at various semi-solid temperature ranges of 560 °C, 580 °C, and 600 °C, holding times of 600, 1200, and 1800 s, and strain rates of 0.1, 0.2, and 0.3 s−1 was studied. From the stress–strain curves and metallographic studies, Arrhenius grain growth model and Avrami dynamic recrystallization model have been formulated by means of linear regression. Parameters such as peak strain, critical strain, recrystallization fraction, and material constants have been found using the above equations. The experimental and calculated values of various material parameters agree with each other, indicating the accuracy of the developed model. Finite element method-based simulations were performed using DEFORM 2D software, and the average grain size obtained from experiments and simulations was validated by means of average grain size. The relative density of the compacted specimens as well as the extruded specimens was also simulated. The simulation results showed that large grains appeared at high temperatures and at the bottom of the specimen.

Surface Modification and its Influence on the Microstructure and Creep Resistance of Nickel Based Superalloy René 77 / Modyfikacja Powierzchniowa Oraz Jej Wpływ Na Mikrostrukture I Wytrzymałosc Na Pełzanie Odlewów Z Nadstopu Niklu Ren´E 77

2013 ◽  
Vol 58 (1) ◽  
pp. 95-98 ◽  
Author(s):  
M. Zielinska ◽  
J. Sieniawski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Surface Modification ◽  
Turbine Blades ◽  
Processing Parameters ◽  
Grain Structure ◽  
Creep Tests ◽  
Cobalt Aluminate ◽  
Nickel Based Superalloy ◽  
Average Grain Size

Superalloy René 77 is very wide used for turbine blades, turbine disks of aircraft engines which work up to 1050°C. These elements are generally produced by the investment casting method. Turbine blades produced by conventional precision casting methods have coarse and inhomogeneous grain structure. Such a material often does not fulfil basic requirements, which concern mechanical properties for the stuff used in aeronautical engineering. The incorporation of controlled grain size improved mechanical properties. This control of grain size in the casting operation was accomplished by the control of processing parameters such as casting temperature, mould preheating temperature, and the use of grain nucleates in the face of the mould. For nickel and cobalt based superalloys, it was found that cobalt aluminate (CoAl2O4) has the best nucleating effect. The objective of this work was to determine the influence of the inoculant’s content (cobalt aluminate) in the surface layer of the ceramic mould on the microstructure and mechanical properties at high temperature of nickel based superalloy René 77. For this purpose, the ceramic moulds were made with different concentration of cobalt aluminate in the primary slurry was from 0 to 10% mass. in zirconium flour. Stepped and cylindrical samples were casted for microstructure and mechanical examinations. The average grain size of the matrix ( phase), was determined on the stepped samples. The influence of surface modification on the grain size of up to section thickness was considered. The microstructure investigations with the use of light microscopy and scanning electron microscopy (SEM) enable to examine the influence of the surface modification on the morphology of ’ phase and carbides precipitations. Verification of the influence of CoAl2O4 on the mechanical properties of castings were investigated on the basis of results obtained form creep tests.

Sign in / Sign up

Export Citation Format

Share Document