scholarly journals The Microstructure and Mechanical Properties of Ferritic-Martensitic Steel EP-823 after High-Temperature Thermomechanical Treatment

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 79
Author(s):  
Igor Litovchenko ◽  
Kseniya Almaeva ◽  
Nadezhda Polekhina ◽  
Sergey Akkuzin ◽  
Valeria Linnik ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Plastic Deformation ◽  
High Temperature ◽  
Thermomechanical Treatment ◽  
Martensitic Steel ◽  
Rolling Plane ◽  
Dynamic Strain ◽  
Temperature Range ◽  
Microstructure And Mechanical Properties

The effect of high-temperature thermomechanical treatment (HTMT) with plastic deformation by rolling in austenitic region on the microstructure and mechanical properties of 12% chromium ferritic-martensitic steel EP-823 is investigated. The features of the grain and defect microstructure of steel are studied by Scanning Electron Microscopy with Electron Back-Scatter Diffraction (SEM EBSD) and Transmission Electron Microscopy (TEM). It is shown that HTMT leads to the formation of pancake structure with grains extended in the rolling direction and flattened in the rolling plane. The average sizes of martensitic packets and ferrite grains are approximately 1.5–2 times smaller compared to the corresponding values after traditional heat treatment (THT, which consists of normalization and tempering). The maximum grain size in the section parallel to the rolling plane increases up to more than 80 µm. HTMT leads to the formation of new sub-boundaries and a higher dislocation density. The fraction of low-angle misorientation boundaries reaches up to ≈68%, which exceeds the corresponding value after HTMT (55%). HTMT does not practically affect the carbide subsystem of steel. The mechanical properties are investigated by tensile tests in the temperature range 20–700 °C. It is shown that the values of the yield strength in this temperature range after HTMT increase relative to the corresponding values after THT. As a result of HTMT, the elongation decreases. A significant decrease is observed in the area of dynamic strain aging (DSA). The mechanisms of plastic deformation and strengthening of ferritic-martensitic steel under the high-temperature thermomechanical treatments are also discussed.

scholarly journals Effect of Multistage High Temperature Thermomechanical Treatment on the Microstructure and Mechanical Properties of Austenitic Reactor Steel

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 63
Author(s):  
Sergey Akkuzin ◽  
Igor Litovchenko ◽  
Nadezhda Polekhina ◽  
Kseniya Almaeva ◽  
Anna Kim ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Temperature ◽  
Thermomechanical Treatment ◽  
Cold Deformation ◽  
Solution Treatment ◽  
The State ◽  
Austenitic Steels ◽  
Dynamic Strain ◽  
Average Grain Size

The deformation microstructures formed by novel multistage high-temperature thermomechanical treatment (HTMT) and their effect on the mechanical properties of austenitic reactor steel are investigated. It is shown that HTMT with plastic deformation at the temperature decreasing in each stage (1100, 900, and 600 °C with a total strain degree of e = 2) is an effective method for refining the grain structure and increasing the strength of the reactor steel. The structural features of grains, grain boundaries and defective substructure of the steel are studied in two sections (in planes perpendicular to the transverse direction and perpendicular to the normal direction) by Scanning Electron Microscopy with Electron Back-Scatter Diffraction (SEM EBSD) and Transmission Electron Microscopy (TEM). After the multistage HTMT, a fragmented structure is formed with grains elongated along the rolling direction and flattened in the rolling plane. The average grain size decreases from 19.3 µm (for the state after solution treatment) to 1.8 µm. A high density of low-angle boundaries (up to ≈ 80%) is found inside deformed grains. An additional cold deformation (e = 0.3) after the multistage HTMT promotes mechanical twinning within fragmented grains and subgrains. The resulting structural states provide high strength properties of steel: the yield strength increases up to 910 MPa (at 20 °C) and up to 580 MPa (at 650 °C), which is 4.6 and 6.1 times higher than that in the state after solution treatment (ST), respectively. The formation of deformed substructure and the influence of dynamic strain aging at an elevated tensile temperature on the mechanical properties of the steel are discussed. Based on the results obtained, the multistage HTMT used in this study can be applied for increasing the strength of austenitic steels.

Microstructure and Mechanical Properties of AZ81 Magnesium Alloy after Unequal Channel Angular Pressing

2013 ◽  
Vol 749 ◽  
pp. 343-348
Author(s):  
Xiao Ping Luo ◽  
Ming Gang Zhang ◽  
Jun Qi Zhou
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Plastic Deformation ◽  
Tensile Strength ◽  
High Temperature ◽  
Magnesium Alloy ◽  
Pressing Temperature ◽  
Angular Pressing ◽  
Microstructure And Mechanical Properties ◽  
Tensile Fractures

The microstructure and mechanical properties of AZ81magnesium alloys after unequal channel angular pressing (UCAP) was investigated using self-made 90° die under different temperature. The results showed that under the same pressing speed, there was a better grain refinement and mechanical property improvement with the decreasing of pressing temperature, however, the tiny cracks on the surface of the processed samples increased. When squeezed at 250 , the average grain was refined from the initial 150um to10um. The tensile strength was changed to 350Mpa, and the elongation was of 10. Tensile fractures presented the increment of dimples structure, which was the result of refined α-Mg matrix and intermetallic compound β-Mg17Al12 phase by severe shear and plastic deformation at high temperature press.

scholarly journals Effects of Orthogonal Heat Treatment on Microstructure and Mechanical Properties of GN9 Ferritic/Martensitic steel

2021 ◽  
Author(s):  
Tingwei Ma ◽  
Xianchao Hao ◽  
Ping Wang
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Heat Treatment ◽  
Yield Strength ◽  
Martensitic Steel ◽  
Orthogonal Design ◽  
Austenitizing Temperature ◽  
Tempering Temperature ◽  
Microstructure And Mechanical Properties ◽  
Cooling Methods

Abstract Microstructure and mechanical properties of GN9 Ferritic/Martensitic steel for sodium-cooled fast reactors have been investigated through orthogonal design and analysis. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimeter (DSC), tensile and impact tests were used to evaluate the heat treatment parameters on yield strength, elongation and ductile-to-brittle transition temperature (DBTT). The results indicate that the microstructures of GN9 steel after orthogonal heat treatments consist of tempered martensite, M23C6, MX carbides and MX carbonitrides. The average prior austenite grains increase and the lath width decreases with the austenitizing temperature increasing from 1000 oC to 1080 oC. Tempering temperature is the most important factor that influences the dislocation evolution, yield strength and elongation compared with austenitizing temperature and cooling methods. Austenitizing temperature, tempering temperature and cooling methods show interactive effects on DBTT. Carbide morphology and distribution, which is influenced by austenitizing and tempering temperatures, is the critical microstructural factor that influences the Charpy impact energy and DBTT. Based on the orthogonal design and microstructural analysis, the optimal heat treatment of GN9 steel is austenitizing at 1000 oC for 0.5 h followed by air cooling and tempering at 760 oC for 1.5 h.

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