Influence Of Thermomechanical Treatment Research Articles

Влияние деформационно-термической обработки на электроcопротивление и упрочнение сплавов Al – 0,2 % Zr и Al – 0,4 % Zr

Влияние деформационно-термической обработки на электроcопротивление и упрочнение сплавов Al – 0,2 % Zr и Al – 0,4 % Zr

Influence of Thermo-Mechanical Treatments on Structure and Mechanical Properties of High-Mn Steel

The aim of this paper is to determine the high-manganese austenite propensity to twinning induced by the cold working and its effect on structure and mechanical properties, and especially the strain energy per unit volume of new-developed high-manganese Fe – Mn – (Al, Si) investigated steel, containing about 24,5 % of manganese, 1% of silicon, 3 % of aluminium and microadditions Nb and Ti with various structures after their heat- and thermo-mechanical treatments. The new-developed high-manganese Fe – Mn – (Al, Si) steel provide an extensive potential for automotive industries through exhibiting the twinning induced plasticity (TWIP) mechanisms. TWIP steel not only show excellent strength, but also have excellent formability due to twinning, thereby leading to excellent combination of strength, ductility, and formability over conventional dual phase steels or transformation induced plasticity (TRIP) steels. Results obtained for high-manganese austenitic steel with the properly formed structure and properties in the thermo-mechanical processes indicate the possibility and purposefulness of their employment for constructional elements of vehicles, especially of the passenger cars to take advantage of the significant growth of their strain energy per unit volume which guarantee reserve of plasticity in the zones of controlled energy absorption during possible collision resulting from activation of twinning induced by the cold working as the fracture counteraction factor, which may result in significant growth of the passive safety of these vehicles' passengers.

Influence of thermo-mechanical treatments on the microstructure and hardness of the Al-2024 alloy

Influence of thermo-mechanical treatments on the microstructure and hardness of the Al-2024 alloy

Improvement of fatigue resistance and ductility of TiAl6V4 processed by selective laser melting

Generative processes or additive layer manufacturing like selective laser melting (SLM) enable the fabrication of highly precise and complex component geometries that are otherwise difficult, costly, or even impossible to realize using conventional techniques. Titanium alloys and in particular TiAl6V4 are suited well for processing by SLM. However, a careful optimization procedure of the process parameters is necessary to obtain a high quality material: firstly, the optimization of the initial process parameters for the minimization of inherent defects, and secondly, the optimization of the further thermomechanical treatment to minimize internal stresses and adjust the microstructure. These two stages of optimization are represented here. For the initial program more than 40 small TiAl6V4 cuboids were produced with the variable scan parameters and two- and three dimensionally analyzed. The reducing of the porosity by 6–10 times is shown. The optimized process parameters were used for further manufacturing of the test specimen, some of them were then thermomechanically treated: annealed or hot-isostatically pressed. The hardness, tensile properties and high cycle fatigue resistance of all samples were tested and the similar tests were also conducted for the reference material: wrought TiAl6V4 alloy. The microstructure, porosity and the received mechanical properties were analyzed and compared, and the influence of thermomechanical treatment was evaluated. As a result of this double optimization, a significant improvement of ductility (ɛ=19.4%) and fatigue resistance compatible to the wrought TiAl6V4 for the SLM produced material was achieved. Furthermore, since some surfaces in complex components such as the channels in the turbine blade cannot be machined or polished, both treated (‘machined’) and untreated (‘as built’) surface conditions were considered and discussed.

Effect of Thermomechanical Treatment on the Environmentally Induced Cracking Behavior of AA7075 Alloy

The influence of thermomechanical treatment on the stress corrosion cracking behavior of AA7075 aluminum alloy forgings was examined in 3.5% NaCl solution by varying the extent of thermomechanical working imparted to each of the conditions. The results show that inadequate working during billet processing resulted in inferior corrosion and mechanical properties. However, more working with intermediate pre-heating stages also led to precipitation of coarse particles resulting in lowering of mechanical properties marginally and a significant reduction in the general/pitting corrosion resistance. The results obtained in the present study indicate that optimum working with controlled pre-heating levels is needed during forging to achieve the desired properties. It is also demonstrated that AA7075 in the over aged condition does not show any environmental cracking susceptibility in spite of the microstructural variations in terms of size and volume fraction of the precipitates. However, the above microstructural variations definitely affected the pitting corrosion and mechanical properties significantly and hence a strict control over the working and pre-heating stages during billet processing is suggested.

Influence of thermo-mechanical treatment and skim milk components on the swelling behavior and rheological properties of starch suspensions

This study focused on the thermal behavior of starch with and without milk proteins. The effects of two thermo-mechanical treatments: at laboratory and pilot scales were studied. Three media were used for starch pasting: NaCl aqueous solution, milk permeate and skim milk. Starch granules significantly swelled more when pasted in the pilot plant or during a longer time of thermo-mechanical treatment at laboratory scale. Moreover, whereas at laboratory scale the presence of lactose or milk proteins did not modify the swelling behavior of starch, a larger increase was obtained in presence of lactose (milk permeate) and milk proteins (skim milk) at pilot scale. At least, different dependence on starch granules diameter ratio versus relative viscosities were obtained at laboratory and pilot scales. Two complementary hypotheses on milk proteins/starch interactions were proposed to explain these results. Indeed, milk proteins could impact starch swelling through an increase of starch granules frictions during thermo-mechanical treatment but also through a modification of their surface characteristics.

Influence of thermo-mechanical treatment on the tensile properties of a modified 14Cr–15Ni stainless steel

The titanium modified 14Cr–15Ni austenitic stainless steel is used as clad and wrapper material for fast breeder nuclear reactor. Thermo-mechanical treatments consisting of solution annealing at two different temperatures of 1273 and 1373K followed by cold-work and thermal ageing have been imparted to the steel to tailor its microstructure for enhancing strength. Tensile tests have been carried out on the thermo-mechanically treated steel at nominal strain rate of 1.6×10−4s−1 over a temperature range of 298–1073K. The yield stress and the ultimate tensile strength of the steel increased with increase in solution treatment temperature and this has been attributed to the fine and higher density of Ti(C,N) precipitate. Tensile flow behaviour of the steel has been analysed using Ludwigson and Voce constitutive equations. The steel heat treated at higher solution temperature exhibited earlier onset of cross slip during tensile deformation. The rate of recovery at higher test temperatures was also influenced by variations in solution heat treatment temperature. In addition, dynamic recrystallization during tensile deformation at higher temperatures was profound for steel solution heat-treated at lower temperature. The differences in flow behaviour and softening mechanisms during tensile testing of the steel after different heat treated conditions have been attributed to the nature of Ti(C,N) precipitation.

Microstructure characterization and mechanical properties of TC4-DT titanium alloy after thermomechanical treatment

Influence of thermomechanical treatments (mill annealing, duplex annealing, solution treatment plus aging and triple annealing) on microstructures and mechanical properties of TC4-DT titanium alloy was investigated. Results showed that thermomechanical treatments had a significant influence on the microstructure parameters and higher annealing and aging temperature and lower cooling rate led to the decrease of the volume fraction of primary α and the size of prior-β and the increase of the width of grain boundary α and secondary α. The highest strength was obtained by solution treatment and aging due to a large amount of transformed β and finer grain boundary α and secondary α at the expense of slight decrease of elongation and the ultimate strength, yield strength, elongation, reduction of area were 1100 MPa, 1030 MPa, 13% and 53% separately. A good combination of strength and ductility has been obtained by duplex annealing with the above values 940 MPa, 887.5 MPa, 15% and 51% respectively. Analysis between microstructure parameters and tensile properties showed that with the volume fraction of transformed β phase and the prior-β grain size increasing, the ultimate strength, yield strength and reduction of area increased, but the elongation decreased. While the width of grain boundary α and secondary α showed a contrary effect on the tensile properties. Elimination of grain boundary α as well as small prior-β grain size can also improve ductility.

Influence of Thermomechanical Treatment on Structure and Crack Propagation in Nanostructured Ti–50.26 at%Ni Alloy

The fatigue propagation of processing-induced microcracks in severely deformed Ti–50.26 at%Ni alloy’s samples was investigated. The processing schedules included cold rolling (CR) with logarithmic strains of ɛ = 0.75 and 1.2, and a combination of CR(ɛ = 1), intermediate annealing (400 °C, 1 h), and warm rolling (ɛ = 0.2, T = 150 °C). The final step of the thermomechanical processing schedules consisted of post-deformation annealing at 400 °C, 1 h. The resulting microstructures were studied using transmission electron microscopy. Using optical microscopy, the processing-induced edge cracks’ lengths and concentrations were measured before and after multicycle superelastic and stress generation/relaxation testing. From the functional fatigue point of view, nanocrystalline (NC) microstructure demonstrated higher tolerance to small cracks than mixed NC + nanosubgrained structure.

Cu-21 mass%Ni-5.5 mass%Sn合金の強度への加工熱処理の影響

Cu-21 mass%Ni-5.5 mass%Sn合金の強度への加工熱処理の影響

Influence of thermomechanical treatment on microstructure and properties of electroslag remelted Cu–Cr–Zr alloy

Effect of thermomechanical treatment (TMT) on aging behavior of electroslag remelted Cu–Cr–Zr alloy was investigated. The relationship between microstructure, mechanical and electrical properties was clarified using hardness, tensile and electrical conductivity testing methods and optical and scanning electron microscopy techniques. The results showed that an appropriate processing and aging treatment may improve the properties of the alloy due to the formation of fine, dispersive and coherent precipitates within the matrix. Indeed, the optimum condition for electrical conductivity and mechanical properties was obtained after cold working of 40% followed by aging at 500°C for 150min.

Microstructure of tool steel upon combined semi-solid processing and thermomechanical treatment

Abstract Semi-solid processing can lead to microstructures with a high proportion of metastable austenite embedded in carbide–austenite network even in ordinary steels. This type of microstructure is a result of non-uniform distribution of alloying elements in a partially melted material. The paper deals with semi-solid processing and heat treatment of the ledeburitic steel with 1.8% carbon and 11% chromium. Its initial microstructure typically consists of ferrite matrix with primary chromium carbides and globular cementite particles. Upon semi-solid processing, the material comprised 95% metastable austenite, predominantly in the form of polyhedral grains with the size of 19 μm. Previous research has demonstrated the grain refinement effect of plastic deformation applied immediately after solidification. In follow-up experiments, the influence of thermomechanical treatment upon subsequent evolution of microstructure was studied. In this experiment, particular attention was devoted to the decomposition of metastable austenite and its contribution to microstructure refinement. Upon the transition through the semi-solid state, the material was cooled down below its solidus temperature and subjected to deformation. This was followed by several cooling schedules. Some of the schedules included a dwell at 600 °C to allow metastable austenite to decompose. Cooling schedules were immediately followed by heating to austenitizing temperature and cooling to room temperature at an equal rate. These procedures produced various types of microstructures. The treatment with the dwell produced mixed-type microstructures with an exceptional form of martensite and partially decomposed carbide network. Processing without the dwell led to the development of microstructures with polyhedral retained austenite grains embedded in the original carbide network. Their hardness ranged from 445 to 850 HV30.

Improvement of the mechanical characteristics of T110 alloy by optimizing its thermomechanical and heat treatment

We study the influence of thermomechanical treatment developed for two-phase α+β-titanium alloys on the microstructure and mechanical characteristics of a new Т110 titanium alloy. As a distinctive feature of the proposed method, we can mention the fact that, prior to hot deformation, the β -solution treatment is performed at a temperature of the single-phase β -region with subsequent cooling at a strictly controlled rate as a result of which it becomes possible to eliminate the negative influence of the initial coarse structure of the α-phase of cast material on the final microstructure and form in the alloy a homogeneous dispersed microstructure with the structure of phases similar to a globular structure in the course of subsequent plastic deformation at a temperature lower than the temperature of completion of the polymorphic transformation T β by 50–70°С. As a result, both the strength and plasticity characteristics increase substantially and simultaneously. The subsequent strengthening thermomechanical treatment with a somewhat elevated temperature of heating for hardening guarantees the increase in the strength up to the maximum high value (1366 MPa) attained for the standard (furnace) methods of heat treatment for sufficiently high levels of plasticity. The indicated balance of strength and plasticity is unique for titanium alloys treated by using the standard furnace methods of heating.

Microstructure and mechanical properties of Ti-35Nb-6Ta alloy after thermomechanical treatment

Abstract The influence of thermo-mechanical treatment on microstructure and mechanical properties of T-35Nb-6Ta has been studied. The thermo-mechanical treatment was chosen to correspond to the production of wire with suitable mechanical properties for dental implants. After casting the alloy was hot forged (700–900 °C), solution treated (850 °C/30 min, water quenched) and cold swaged (reductions up to 91%). The annealing (700 °C/3 h/furnace) or aging (450 °C/8 h/furnace) was used as final heat treatment. The microstructure was studied by using light microscopy, scanning electron microscopy, transmission electron microscopy and XRD analysis. Cold swaging introduces microstructure consisting of highly deformed β-phase grains with dislocation tangles and twins, which ensures high tensile strength about 820 MPa, low Young's modulus (~ 50 GPa) and good ductility ~ 10%. Subsequent aging increases tensile strength (1000 MPa) as well as Young's modulus (75 GPa) without diminishing ductility. Annealing at 700 °C slightly decreases tensile strength (730 MPa) and increases the ductility and Young's modulus (17% and 62 GPa respectively). The mechanical properties attained recommend the thermo-mechanical treatment for production of wires for dental implants.

The Influence of Thermomechanical Treatment on the Microstructure and Properties of a Wrought Al-Mg-Si Alloy

. To investigate the effects of thermomechanical treatments (TMT) on the microstructure and properties of Al-Mg-Si alloy, the cold deformation on the ageing precipitation of a solution-treated Al-Mg-Si alloy was studied. The results shows that the time of reaching the peak hardness is shortened with the increasing deformation and an obvious increasing in the peak hardness and tensile strength are occured with higher amount of deformations. The microstructures of peak hardness reveals that the average size of the precipitates becomes smaller in size and greater in number in the alloy with 50% deformations. The study is also carried out to investigate the changes in resistivity of alloys during the ageing time in the alloy with and without 50% deformation. It was found that there are rapidly increasing in resistivity followed by decreasing with the onset of ageing time in both cases. However, the extent of increasing and decreasing in resistivity is much stronger in the alloy with 50% deformation. These results were discussed according to the effects of cold deformation on the dislocations and precipitates in the Al-Mg-Si alloy.

Influence of thermomechanical treatment and alloying on the properties of high-carbon wire rod

Kinetic data on austenite decomposition in high-carbon alloy steel in the continuous cooling of wire rod permit the determination of the best thermomechanical treatment. Regulation of the chemical composition of the steel (the carbon, chromium, and manganese content) and optimal thermomechanical treatment ensure the structure and properties of the wire rod for superhigh-strength wire and metal cord.

Influence of thermomechanical treatment on the hardening mechanisms and structural changes of a cast Cu–6.6 wt.%Ag alloy

Investigations were carried out on the cast samples of Cu–6.6 wt.%Ag alloy, as well as pure copper samples, for the sake of comparison. Cast samples of copper and alloy were subjected to the same thermomechanical treatment. The thermomechanical treatment included the homogenized annealing, prefinal cold rolling, solution annealing, final cold rolling with a final reduction of 20%, 40% and 60% as well as the isochronal and isothermal annealing up to the recrystallization temperature. Influence of thermomechanical treatment on the hardening mechanisms and structural changes of cast Cu–6.6 wt.%Ag alloy has been investigated for the hardness and electrical conductivity measurements as well as optical microscopy. The study has shown that the anneal hardening effect appeared on the cast Cu–6.6 wt.%Ag alloy in the temperature range of 160–400 °C and was followed by an increase in the hardness and electrical conductivity.

The influence of thermo-mechanical treatment on the structure and plasticity of FeAl intermetallic phase–base alloy

Alloys based on intermetallic phases from the Fe-Al system they belong to a group of high-temperature creep resisting materials of advantageous physicochemical and mechanical properties at an elevated and high temperature. In general, limitation on the capacity for a broad application of intermetals from the Fe-Al system, e.g. as an alternative to expensive alloy steels of specific properties, is their insufficient plasticity, which is a factor inhibiting further their development as constructional materials. Under this study, research has been conducted on the capacity for forming alloys based on intermetallic phases from the Fe-Al system, via thermo-mechanical processing. In the present work, the possibility of forming Fe-Al-intermetallic-phase-based alloys in thermo-mechanical treatment (TMT) has been studied. After casting and annealing, alloy specimens were subjected to axial-symmetric compression in the Gleeble 3800 simulator in the range of 700–1200 °C at 0.01, 0.1, 1.0, 10 s−1 strain rates. In order to analyze the processes which take place during deformation, the specimens after deformation were intensely cooled with water. Structural examination was carried out using light and electron microscopy. The impact of hot rolling process parameters on the structure of intermetallic-phase-based FeAl alloys and properties has been determined. The results will constitute the basis for modelling the structural changes in FeAl intermetallic alloy.

Correlation between mechanical properties and structural changes of the sintered Cu-4 at% Ag alloy during thermomechanical treatment

Influence of thermomechanical treatment on micro structure and strength (hardness and microhardness) of the sintered copper based Cu-4 at% Ag alloy was investigated using Vickers hardness and microhardness measurements, and optical microscopy. After sintering at 790?C, samples of Cu-4 at% Ag alloy were subjected to thermomechanical treatment by cold rolling with 20, 40 and 60% deformation degrees, and annealing below and over the recrystallization temperature. It was shown that microstructure of Cu-4 at% Ag alloy changed with thermomechanical treatment, which directly causes changes of mechanical properties. Optical microphotograph of the sintered Cu-4 at% Ag alloy shows relatively homogeneous structure with spherical pores presented. The strength (hardness and microhardness) of the sintered Cu-4 at% Ag alloy during cold rolling increases with deformation degree due to deformation strengthening. Maximum values of hardness and microhardness were for 60% deformation. The porosity still exists in spite of the fact that compacting was carried out during the cold rolling. The hardness and microhardness continue to increase after annealing at temperature bellow recrystallization temperature due to anneal hardening effect which occurs in a temperature range of 160-350?C. It was concluded that solute segregation to dislocations, analogous to the formation of Cottrel atmosphere in interstitial solid solutions, is primarily responsible for anneal hardening phenomenon. Annealing at higher temperatures (higher than 400?C) results in strength decrease due to beginning of alloy recrystallization.

On the influence of thermomechanical treatments on the microstructure and phase transformation behavior of Ni–Ti–Fe shape memory alloys

The present work shows how the microstructure and the phase transformation behavior of as-cast Ti-48 at.% Ni-2 at.% Fe shape memory alloys respond to different thermomechanical treatments. The applied procedures involve homogenization, swaging at different temperatures and recrystallization annealing. The as-cast material is characterized by a coarse-grained microstructure. During repeated hot working in combination with recrystallization treatments, a fine-grained microstructure evolves in the surface volume of the swaged Ni–Ti–Fe rod. In contrast, its center remains almost unaffected by recrystallization (because less dislocations are introduced during swaging and recovery processes are more intense). This type of microstructural heterogeneity can be avoided by cold work at the end of the thermomechanical procedure. Swaging at low temperatures results in higher dislocation densities and thus in a more homogeneous microstructural evolution during recrystallization. In the cold-worked state, the phase transition R → B19′ is strongly impeded by the presence of dislocations, whereas the transition characteristics of the recrystallized and of the non-deformed original material state almost coincide.