STUDY OF THE MICROSTRUCTURE OF MARTENSITE-BAINITE STEELS AND NICKEL ALLOYS WHEN MODELING HEAT TREATMENT MODES USING A DILATOMETRIC METHOD

2019 ◽  
Vol 85 (6) ◽  
pp. 30-36
Author(s):  
N. V. Lebedeva ◽  
Yu. M. Markova ◽  
A. I. Ziza ◽  
D. M. Anisimov
Keyword(s):  
Heat Treatment ◽  
Thermomechanical Processing ◽  
Production Costs ◽  
Grain Structure ◽  
Helium Atmosphere ◽  
Fine Grained ◽  
Dilatometric Method ◽  
Combined Application ◽  
Fine Grained Structure

We present the results obtained using the equipment available at the Center for collective use “Composition, structure, properties of structural and functional alloys” NRC “Kurchatov Institute” — CRISM “Prometey”: DIL 805A/D (TA Instruments) and DIL 402C (Netzsch) dilatometers. Dilatometric analysis which provides determination of the temperature coefficient of linear expansion and the temperature of phase transitions, as well as evaluation of the transformation kinetics, can also allow simulation of heat treatment modes to identify the size of the former austenitic grain using vacuum etching and conduct the research aimed at improving the technology of thermal and thermomechanical processing (TMO) of steels and alloys. The experiments were carried out both in vacuum and in dynamic helium atmosphere. The main methodological difficulties that we have faced with are described. For steels of martensite and martensite-bainite class (38KhMA, 38KhN3MFA, 20Kh3NMFA) conditions of vacuum etching in the chamber of the dilatometer are specified. The efficiency of the method for martensite-bainite steels in determination of the grain size compared to traditional methods of etching is deminstrated. The effect of thermodeformation parameters on the size of austenitic grain is estimated. When modeling the heat treatment modes by the dilatometric method, the microstructure of KhN55MVTs nickel alloy was also analyzed. Changes in the size and morphology of the grain structure at different stages of heat treatment are revealed. The obtained results were used to adjust the current modes of heat treatment and obtain a uniform fine-grained structure. The combined application of dilatometric and metallographic analyzes after vacuum etching of the material decreases the production costs attributed to obtaining the desired microstructure upon thermal and thermomechanical processing of the products and blanks.

Microstructure Evolution of Nickel-Based Superalloys Induced by Thermomechanical Processing - Simulation and Verification

2018 ◽  
Vol 385 ◽  
pp. 424-429 ◽  
Author(s):  
Shamil Mukhtarov ◽  
Farid Z. Utyashev ◽  
Ruslan Shakhov
Keyword(s):  
Microstructure Evolution ◽  
Thermomechanical Processing ◽  
Strain Rates ◽  
Microstructure Formation ◽  
Turbine Engine ◽  
Fine Grained ◽  
Gamma Prime ◽  
Deflected Mode ◽  
Fine Grained Structure ◽  
Prime Phase

It is known that different parts of the gas turbine engine discs are operated at different temperature and load. Therefore, it is advisable to make such components out of nickel-based superalloys with a regulated structure that provides them the best operational properties. It is important to know the thermomechanical treatment for their processing to form such structures. Research of the deformation behavior and the microstructure evolution of nickel-based superalloys were carried out on small specimens. The accumulated strains and the stress distribution in specimens were determined during simulation. It is possible to predict structure formation on the basis of a deflected mode. Verification was carried out by isothermal upsetting of specimens out of superalloys at the temperature and strain rates determined by simulation. Thermomechanical treatments of the superalloys for different microstructure formation were defined. The features of the microstructure formation are shown depending on the chemical and phase composition of the alloys. Hot deformation of the ATI Allvac 718Plus superalloy leads to dissolution of the gamma prime phase that facilitates the deformation capacity. Increasing the alloyage of superalloys, including rhenium, leads to formation of a necklace structure instead of a homogeneous fine-grained structure for less alloyed superalloys at the same strain.

Influence of Thermal Cyclic Deformation and Hardening Heat Treatment on the Structure and Properties of Steel 10

2015 ◽  
Vol 788 ◽  
pp. 187-193 ◽  
Author(s):  
Aleksandr Prudnikov ◽  
Marina Popova ◽  
Vladimir Prudnikov
Keyword(s):  
Heat Treatment ◽  
Cyclic Deformation ◽  
Sheet Steel ◽  
Strength Characteristics ◽  
Rolled Sheet ◽  
Structure And Properties ◽  
Fine Grained ◽  
Fine Grained Structure ◽  
Hot Rolled ◽  
Hardening Heat Treatment

The results of the influence of preliminary thermal cyclic deformation and subsequent hardening heat treatment on the microstructure and mechanical properties of hot-rolled sheet steel 10 are presented. It is shown that the use of preliminary thermal cyclic deformation of the steel 10 stock material results in a fine-grained structure of a hot-rolled sheet (3 mm thick) produced by an industrial technology. Deformation occurred at a temperature above AC3 (1250 °C), with cooling to 200-300 °C during 10 cycles and the deformation ratio per cycle being 6-8 %. Such a treatment before sheet hot-rolling allows increasing the strength characteristics (tensile strength, yield strength) by almost 30 %. It has been established that the use of subsequent heat treatment (quenching, 900 °C, water and tempering 1 h, 600 °C) leads to a further increase in strength characteristics by 15-20% while maintaining a sufficient level of ductility of sheet steel.

Thermoelectric properties of germanium telluride with fine-grained structure

2020 ◽  
Vol 11 ◽  
pp. 15-25
Author(s):  
L. D. Ivanova ◽  
◽  
Yu. V. Granatkina ◽  
I. Yu. Nikhezina ◽  
A. G. Malchev ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Melt Spinning ◽  
High Energy ◽  
Grain Structure ◽  
Thermoelectric Efficiency ◽  
Fine Grained ◽  
Germanium Telluride ◽  
Fine Grained Structure ◽  
Properties Of Materials ◽  
P Type

The microstructure and thermoelectric properties of materials based on germanium telluride p-type conductivity doped with copper and bismuth obtained by hot pressing of three types powders prepared by grinding an ingot to a size of hundreds microns (0.315  mm) to hundreds of nanometers (mechanical activation) in planetary high-energy mill and melt spinning were investigated. The microstructure of the samples were analyzed by optical and electron scanning microscopies. The nanoscale grain structure of these samples was established. The thermoelectric characteristics of the materials: Seebeck coefficient, electrical and thermal conductivities, were measured both at room temperature and in the temperature range of 100 – 800 K. The slopes of these dependencies are estimated. The coefficient of thermoelectric figure of merit is calculated. The higher thermoelectric efficiency (ZT = 1.5 at 600 K) was received for the samples hot-pressed from granules, prepared by melt spinning.

Grain Structure and Precipitates in Squeeze Casting Al-Li-Mg-Zr Alloy

2014 ◽  
Vol 887-888 ◽  
pp. 329-332
Author(s):  
Li Fan ◽  
Zhong Wei Chen ◽  
Qi Tang Hao
Keyword(s):  
Grain Boundaries ◽  
Squeeze Casting ◽  
Grain Structure ◽  
Fine Grained ◽  
Fine Grain ◽  
The Matrix ◽  
Fine Grained Structure ◽  
Heat Treated Condition ◽  
Micrometer Size ◽  
Zr Alloy

Grain structure and precipitates in squeeze casting Al-Li-Mg-Zr alloy for aircraft industry were investigated in heat treated condition, using X-ray diffraction, optical microscopy and transmission electron microscopy. An ultra fine grained structure in sub-micrometer size was obtained, having fine nanograins in it with polycrystalline diffraction rings that are different from the single-crystal patterns in the matrix. Ultra fine grain areas are generally located on the grain boundaries and sub-grain boundaries. In addition, TEM observations indicates the presence of lenticular δ' (Al3Li) phases that symmetrical distributed around the GP zones. The alloy also contains spherical β' (Al3Zr) dispersoids, and S1 (Al2MgLi) phases.

scholarly journals Thermocyclic treatment (tcт) of metals - way for getting optimum structures and properties

2019 ◽  
pp. 238-252
Author(s):  
O.N. Perkov ◽  
I.A. Vakulenko ◽  
V.M Kuzmychov
Keyword(s):  
Heat Treatment ◽  
Heating Temperature ◽  
Rapid Heating ◽  
Metal Structure ◽  
Treatment Method ◽  
Repeated Heating ◽  
Fine Grained ◽  
Heating And Cooling ◽  
Fine Grained Structure ◽  
Rapid Coarsening

The aim of this work is to study the basic principles of thermal cyclic processing (TCТ) of metals to obtain structures that determine the optimal complex of mechanical properties. The basic provisions of metal heating centers using periodically repeated heating and cooling cycles are given. The TCТ method, as a heat treatment method, is based on constant accumulation from cycle to cycle of positive changes in the structure of metals. Studies have shown that with rapid heating, the growth of austenitic grain occurs slowly and, therefore, heating to high temperatures (up to 10000C) does not lead to an intensive increase in grain. It has been established that grain size increases at a variable heating temperature 3 times slower than under isothermal conditions at the corresponding temperature. Provided that the growth rate of the new phase (austenite) is small and the nucleation rate of grains is significant, it turns out that by the end of the a®g transformation, a fine-grained structure is retained. Further heating or holding at a constant temperature leads to a rapid coarsening of austenite grains. If cooling (for example, in air) of rapidly heated steel is performed 10–150C higher than the temperature of the Ас1 point, then fine perlite grain is formed due to reverse recrystallization. With one thermal cycle, ferrite in subeutectoid steels almost does not undergo changes. But if several such heating and cooling are performed, then the entire ferrite-pearlite structure undergoes a change. It has been established that the higher the heating rate during heating and heating and the less overheating above Ас1, the finer the grain in carbon structural steel. However, this increases the need to increase the number of heat treatment cycles. The mechanism of structure formation explaining these phenomena and practical recommendations on the implementation of the process of the technical and economic process are presented. This approach makes it possible to form the optimal metal structure. At the same time, opportunities can be significantly expanded in terms of obtaining materials with desired properties and improving on this basis machines, structures, individual units and parts. All this puts TCТ in the category of promising areas in metalworking.

The Microstructure of Melt-Spun Iron Neodymium Permanent Magnet Materials

1985 ◽  
Vol 43 ◽  
pp. 210-211
Author(s):  
R. C. Dickenson
Keyword(s):  
Heat Treatment ◽  
Magnetic Properties ◽  
Melt Spinning ◽  
Ion Milling ◽  
X Ray ◽  
Fine Grained ◽  
Cold Stage ◽  
Melt Spun ◽  
Fine Grained Structure ◽  
Permanent Magnet Materials

Rapidly-quenched iron rare-earth boron alloys, with appropriate heat treatment, exhibit commercially promising permanent magnetic properties. This paper will report the results of an AEM characterization undertaken to explain the origin of the magnetic properties of an iron-neodymium-boron alloy in terms of its microstructure. Ribbons of Fe76 Nd16 B8 were prepared by melt-spinning, and were subsequently annealed at 700°C for 6 minutes to promote growth of a fine-grained structure. Samples were prepared for AEM by ion-milling the ribbons on a cold stage and examined using a Philips 400T TEM/STEM equipped with an energy dispersive x-ray unit.Three different microstructures are commonly observed in these alloys, and several others have been found in isolated cases.

Surface layer modification by cryogenic burnishing of Al 7050-T7451 alloy with near ultra-fine grained structure

2021 ◽  
pp. 1-22
Author(s):  
Bo Huang ◽  
Yusuf Kaynak ◽  
Ying Sun ◽  
Marwan Khraisheh ◽  
I. S. Jawahir
Keyword(s):  
Surface Integrity ◽  
Surface Hardness ◽  
Grain Structure ◽  
Fine Grained ◽  
Compressive Stresses ◽  
Wear And Corrosion ◽  
Cryogenic Burnishing ◽  
Subsurface Layers ◽  
Fine Grained Structure ◽  
Wear And Corrosion Resistance

Abstract Burnishing has been increasingly utilized to improve the surface integrity of manufactured components. The generation of surface and subsurface layers with ultrafine grains, attributed to severe plastic deformation and dynamic recrystallization, leads to improved surface integrity characteristics including surface and subsurface hardness and reduction in surface roughness. Additionally, due to the generation of compressive stresses within the refined layers, increase in fatigue life and improved wear and corrosion resistance can be achieved. In this study, we apply cryogenic burnishing on Al 7050-T7451 discs and compare the surface integrity characteristics with dry conventional burnishing. A special roller burnishing tool with flexible rotating roller head was designed and used to perform the cryogenic burnishing experiments using liquid nitrogen as the coolant. The results show that cryogenic burnishing can increase the surface hardness by an average of 20-30% within a layer depth of 200 μm compared to only 5-10% increase using dry conventional burnishing. Refined layers with nano grain structure were also generated. During cryogenic burnishing the tangential burnishing forces were higher than those of dry conventional burnishing due to rapid cooling and work hardening of the material.

Grain Refinement of 6061 Al Alloy by the Modified Strain-Induced Melt- Activated(SIMA) Process for Semi-Solid Processing

2007 ◽  
Vol 119 ◽  
pp. 311-314 ◽  
Author(s):  
Young Buem Song ◽  
Chun Pyo Hong
Keyword(s):  
Grain Refinement ◽  
Grain Structure ◽  
Al Alloy ◽  
Fine Grained ◽  
Fine Grain ◽  
Fine Grained Structure ◽  
Size Uniformity ◽  
Sima Process ◽  
Semi Solid ◽  
6061 Al Alloy

The dynamic process of fine grain evolution of 6061 aluminum alloy during modified strain-induced, melt-activated (SIMA) process was studied. The modified SIMA process employed casting, two stage homogenization, warm multi-forging, and recrystallization and partial melting (RAP). Multi-forging was carried out at a strain rate of 9x10-3 s-1 to accumulate high strains, with decreasing temperature from 250 to 200 °C. The alloy multi-forged with the accumulated strain of about 12 and RAP at 640 °C for 10 min exhibited the uniform equiaxed recrystallized grain structure. Accordingly, it was evident that multi-forging was very effective on grain refinement and grain size uniformity. The present modified SIMA process was discussed as an alternative thermo-mechanical processing for preparing the alloys with fine grained structure for semi solid processing.

Structure and Hardness of the ZnAl40Cu(1-2)Ti(1-2) Alloys

2016 ◽  
Vol 246 ◽  
pp. 47-50 ◽  
Author(s):  
Tomasz Mikuszewski ◽  
Rafał Michalik
Keyword(s):  
Optical Microscope ◽  
Scanning Microscope ◽  
Titanium Addition ◽  
Fine Grained ◽  
Cu Alloys ◽  
Hardness Tests ◽  
Fine Grained Structure ◽  
Solution Strengthening ◽  
The Subject

The purpose of the examination was to determination of influence of microstructure and hardness of Zn-Al-Cu alloys with titanium addition. The subject of examination was were ZnAl40Cu2Ti, ZnAl40Cu1.5Ti1.5 and ZnAl40Ti2Cu alloys. The scope of test included Brinell hardness tests, tests on optical microscope, tests on scanning microscope and X-ray microanalysis. It was found that tested ZnAl40Cu(1-2)Ti(1-2) alloys are characterized by homogeneous, fine- grained structure. Carried out tests pointed out, that addition of titanium to ZnAl40Cu(1-2)Ti(1-2) alloy influences on hardness increasing. It was also found, that the titanium forms Ti-Al precipitates in ZnAl40Cu(1-2)Ti(1-2) alloys and does not take part in solution strengthening process.

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