Effect Of Thermomechanical Treatment Research Articles

Effect of thermomechanical treatment on the cold resistance of low-carbon low-alloy welding steel

Effect of the structure and texture formed upon thermomechanical treatment (TMechT) on the cold resistance of low-carbon low-alloy welding steel is considered. The structure has been investigated by the metallographic and electron-microscopic methods; the texture has been studied by X-ray diffraction method with the aid of the analysis of the orientation distribution function (ODF). Structural factors that affect an increase in the cold resistance, including creation of a submicrocrystalline structure, have been considered. It has been established that the components of the texture result from a regular crystallographic rearrangement of the texture of hot deformation of austenite into the texture of the α phase upon the γ → α transformation. It is shown that the dependence of the cold resistance of the rolled sheet on the fraction of the cube component in the texture of the α phase has a complex nonmonotonic nature.

Effect of thermomechanical treatment on microstructure and hardness behavior of AZ63 magnesium alloy

Due to their high specific strength and low density, magnesium alloys are widely used in many weight-saving applications. This research is aimed at investigating the microstructure and hardness of commercial AZ63 alloy specimens subjected to two different thermomechanical treatments (TMTs). For the first TMT, after solution treated at the temperature of 380 °C for 20 h, AZ63 alloy specimens were 5% cold worked by rolling process followed by ageing at the temperatures of 150 °C and 250 °C for 3, 9 and 25 h. In the second TMT, the specimens were solution treated at the temperature of 380 °C for 20 h, underwent 2% cold worked and quenched in water of 0 °C. Half of the specimens were then 2% cold worked whilst the rest were rolled to 8% cold worked. All the specimens were then aged at the temperatures of 150 °C and 250 °C for 3, 9 and 25 h. Optical microscope was used to analyze the microstructures of the specimens. Hardness test was too conducted to measure the effect of the treatments on the specimens. Results show that two-step aging enhances the hardness of the specimens due to the distribution of fine β -phase (Mg 17 Al 12 ) in the alloy matrix. The results also reveal that, the best hardness from the first TMT was produced by specimen that was pre-aged at 150 °C whereas, in the second TMT, aging at 250 °C exhibited the best hardness values.

Thermomechanical effect on magnetic behaviors of antiferromagnetic Mn-Fe(Cu) alloy

The effect of thermomechanical treatment on the magnetic properties of Mn 85.5Fe 9.0Cu 0.5 alloy was studied by use of a materials testing machine, a vibrating sample magnetometer, an X-ray diffractometer, a homogeneously and adjustably magnetic field and strain gauges. The results show that the orientation of fct phase and magnetic domains is affected by the thermomechanical treatment. When the compressive strain of thermomechanical treatment is −1.2%, the magnetic-field-induced strain reaches the highest value in the adapted situation.

Artificial neural network to predict the effect of thermomechanical treatments on bake hardenability of low carbon steels

Artificial neural network (ANN) is a powerful tool in optimizing many industrial processes. In the present study, an ANN was developed to model and predict the bake hardenability and final yield stress of low carbon steels. Five parameters affecting the bake hardening were considered as inputs, including the annealing/reheating temperature, cooling rate, initial yield stress, work hardening and carbon level. The network was then trained so that to predict the bake hardening amounts and the final yield stress as outputs. A Multilayer cascade-forward back-propagation network is developed and trained using experimental work. Two low carbon steels, St12 and St14, were investigated. The effects of annealing/reheating temperature (500–1000 °C) and subsequent cooling rate (0.5, 5 and 500 °C/s) on the bake hardenability of steels were modeled by ANN as well. In terms of cooling rate, two different behaviors were observed. The bake hardenability of St12 was increased from 13 ± 2, for reheating to 500 °C, to 88 ± 2 MPa for the reheating temperature of 1000 °C. As for St14, these values were respectively 8 ± 2 and 67 ± 2 MPa. The predicted values are in very good agreement with the measured ones indicating that the developed model is very accurate and has the great ability for predicting the bake hardenability.

Effect of thermomechanical treatment on the corrosion of AA5083

Corrosion resistance degradation induced by the presence of β-phase (Al 3Mg 2) limits the performance of aluminum alloy 5083 for some critical applications. The effect of thermomechanical treatment on the corrosion of AA5083 is presented in this paper. The samples subjected to the thermomechanical treatment showed superior corrosion resistance compared to the as-received samples. The effects of grain boundary character distribution, grain shape, texture, and precipitates on corrosion are discussed based on experimental observations. Special boundaries are expected to have a weak effect on the overall corrosion resistance of the material compared to the other factors.

Effect of Thermomechanical Treatment on the Grain Boundary Character Distribution in a 9Cr-1Mo Ferritic Steel

Grain boundary embrittlement due to segregation of impurities to high-energy grain boundaries causing an increase of ductile-brittle transition temperature poses a major obstacle in the development of ferritic steel for nuclear reactor core applications. Various types of thermomechanical treatments were carried out on the modified 9Cr-1Mo steel, and the nature of grain boundaries was evaluated using electron backscattered diffraction (EBSD); the “effective grain boundary energy” (EGBE) was also computed. The minimum EGBE was obtained in a specimen that was deformed in the austenite phase field at 1323 K and further normalized and tempered. This condition also gave a high fraction of coincident site lattice boundaries compared to the normalized and tempered modified 9Cr-1Mo steel.

Effects of thermomechanical treatment on the mechanical properties and microstructures of 6013 alloy

The mechanical properties and microstructures of 6013 alloy after different thermomechanical treatments were investigated. The detailed dislocation configurations after deformation and morphologies of age hardening precipitates were examined through transmission electron microscopy (TEM). The experimental results show that the thermomechanical treatment can significantly enhance the strength of 6013 alloy, and has a similar influence trend on single and two-step aging behaviors. With the increasing deformation ratio, the peak-hardness (HVmax) increases, the time to HVmax shortens, and the density of tangled dislocation network increases. The aging precipitates become larger and inhomogeneous by applying thernomechanical treatment.

Effects of Thermomechanical Treatments on Pseudoelastic Strain Characteristics of Ti-29Nb-13Ta-4.6Zr for Biomedical Applications

There is a possibility for β-type Ti-29Nb-13Ta-4.6Zr (TNTZ) to exhibit super-elastic characteristics, which is advantageous for biomedical applications such as orthodontic wires. Thermomechanical treatments are expected to induce super-elastic characteristics in β-type titanium alloys. Therefore, TNTZ specimens were subjected to various thermomechanical treatments, including solution treatments and severe cold rolling, wherein the second solution treatment temperature, second solution treatment time, and reduction ratio of cold rolling were varied in order to investigate the elastic deformation characteristics. One of the thermomechanical treatments induces super-elastic characteristics in a TNTZ specimen. In particular, a highest total pseudoelastic strain of 2.8% is measured in the TNTZ specimen subjected to the thermomechanical treatment at a cold rolling reduction ratio of 95%, second solution treatment temperature of 1073 K, and second solution treatment time of 0.3 ks. Tensile loading and unloading stress-strain curves of the TNTZ specimens subjected to various thermomechanical treatments indicate a high total pseudoelastic strain and exhibit three step deformation process. An α martensite phase is formed in the TNTZ specimen subjected to the thermomechanical treatment carried out under the above mentioned conditions.

Effect of thermo-mechanical treatments on the microstructure of micro-alloyed low-carbon steels

Micro-alloyed steels are known to exhibit superior mechanical properties through controlled rolling and specific thermo-mechanical treatments. Steel strength directly comes from a controlled precipitation process of carbides, nitrides and carbo-nitrides formed during the thermo-mechanical treatment, which are responsible for the fine-grained ferritic structure. In the present study, four different micro-alloyed, low-carbon steels have been studied: one baseline steel containing a small fraction of Al and N, and the other three with different fractions of Nb and V. Two thermo-mechanical treatments, which differed in the γ → α transformation temperature were evaluated. Micro-strengthening contributions of the carbo-nitrides were determined using the Ashby-Orowan approach on the basis of TEM characterization. It was found that for the all four steels the Ashby-Orowan approach was in quite good agreement with the bulk yield strength (σy), as determined by mechanical testing steel (accounting for 0.8σy). The pinning force of the particles was also calculated and compared to the recrystallization driving force. The steel containing Nb + V exhibited the highest pinning force, but the low fraction of the alloying elements, made this contribution only a fraction of ~1/3 with respect to the recrystallization driving force.

Effects of thermo-mechanical treatment on a Fe–30Mn–6Si shape memory alloy

Effects of thermo-mechanical treatment on a Fe–30Mn–6Si shape memory alloy were investigated, including the microstructure, precipitation behavior and shape memory performance. Experimental results show that the as-cold-rolled specimen exhibits a worse shape recovery, and its M s temperature and transformational enthalpy (Δ H) are much lower than those of as-annealed one. Specimens with 10% cold-rolling and subsequent 550–650 °C aging have lots of (Fe, Mn) 3Si precipitates within the grain interior. These precipitates exhibit a D0 3 structure with lattice constant of 5.66 Å, and show a near orientation relationship with γ austenite as [ 1 ¯ 1 1 ] D 0 3 / / [ 0 1 1 ] γ , ( 2 ¯ 0 2 ¯ ) D 0 3 / / ( 1 ¯ 1 ¯ 1 ) γ . The 550–650 °C aged specimen can exhibit high shape recovery ratios, due to the contributions of effective nuclei and well-aligned precipitates within the grain interior. If the aging temperature is higher than 750 °C, the recrystallization occurs and the disappearance of both effective nuclei and well-aligned precipitates within the grain interior will obviously reduce the specimen's shape memory performance.

Sintered High Carbon Steels: Effect of Thermomechanical Treatments on their Mechanical and Wear Performance

In this work, ultrahigh carbon steels (UHCS) obtained by powder metallurgy with CIP and argon sintered at 1150°C. Then, they were rolled at 850 °C with a reduction of 40 %. Finally, steels were quenched at 850 and 1000 °C in oil. In each step, hardness, bending strength and wear performance were evaluated. Obtained results are justified with a metallographic study by SEM. Both mechanical properties and wear resistance are highly favoured with the thermomechanical treatment that removes the porosity of the material. Moreover, final quenching highly hardens the material. The obtained material could be used as matrix for tool steels.

Evolution of Special Grain Boundaries in Austenitic Steels

AISI 304 type austenitic stainless steel samples were subjected to different thermomechanical treatments in order to investigate the effect of thermo-mechanical treatment on the grain boundary structure of the material. Electron back scatter diffraction measurements have been carried out in order to obtain information about the boundaries of the treated specimen. The measurements showed that achieving the same deformation with the same number of deformation cycles and same heat treatment temperature, the application of shorter heat treatment holding time was advantageous in aspect of grain boundary structure comparing to the thermo-mechanical treatments with longer holding time. The frequency of the special Σ3n type CSL-boundaries excluding coherent twin boundaries was significantly decreased by increasing the heat treatment holding time of the samples from the very short heat treatment periods. Extending the holding time further, the frequency of the special Σ3n type CSL-boundaries excluding coherent twin boundaries increased and reached the results applying the shorter heat treatment periods.

Effect of thermomechanical treatment on the mechanical properties of an Al–Cu–Mg alloy

The effects of a new thermomechanical treatment on the microstructures and mechanical properties of an Al–Cu–Mg alloy have been studied. It has been shown that the mechanical properties of the alloy have substantially been improved by the new thermomechanical process. Most importantly, the anisotropy is much lower. Microstructural analysis indicated that the improvements in the mechanical properties and decrease in the anisotropy are due to the high dislocation density, strong interaction between dislocations and precipitates, and dispersed distribution of the needle-shaped precipitates.

Effects of thermo-mechanical treatments on mechanical properties of AA2219 gas tungsten arc welds

Abstract Fusion zone of AA2219 alloy gas tungsten arc welds was subjected to compressive deformation by rolling the crown of the weld in the welding direction. Twelve percent compressive deformation improved the as-weld hardness from 75 to 100 VHN. The yield strength increased from 125 to 220 MPa. The welds made by pulsed current technique exhibited better strength and ductility compared to their continuous current weld counterparts, both in the as-welded condition and the deformed condition. The improvement in strength was found to be due to dislocation loops formed near the grain boundaries in the fusion zone. Direct aging of fusion zone at 190 °C, increased the yield strength significantly from 125 to about 200 MPa. Aging of the deformed fusion zone did not improve tensile strength further.

Effect of TMT Process on the Strength and Precipitation Behavior of an 11Cr-0.3Mo-1.6W Steel during Long Term Aging

The effect of thermo-mechanical treatment (TMT) process on the strength and precipitation behavior of an 11%Cr-0.3Mo-1.6W steel during long term aging was investigated. The major precipitates in as-tempered specimen were identified as M23C6 (M=Fe,Cr) and MX (M=Ta,V;X=C,N). The M23C6 precipitate in TMT sample was more finely distributed due to the increased heterogeneous nucleation sites at dislocations. The tensile strength of TMT sample is higher than that of the conventional heat treatment (CHT) sample in as-tempered condition. However, Laves phase starts to precipitate additionally in the aged condition. The growth rate of Laves phase in TMT sample is much faster than that in CHT sample. Therefore, the difference in tensile strength between CHT and TMT sample decreases as the aging time increases.

The Effects of Thermo-Mechanical Treatment on the Properties of 2519 Aluminum Alloy

A procedure of thermo-mechanical treatment (TMT) was carried out to 2519 aluminum alloy to improve its properties. The influences of cold deformation ratio, ageing temperature and ageing time of the TMT on the mechanical properties and electrochemical corrosion resistance of this alloy were investigated. The results show that after TMT the tensile strength of 2519 aluminum alloy can be improved obviously but its electrochemical corrosion resistance decreases slightly. The optimum processing parameters of the TMT for 2519 aluminum alloy can be described as: solid solution at 530°Cfor 0.5h, then cold deform with a ratio of 15% followed by aging at 150°C for 10h.

Optimized Thermomechanical Treatment for Strong and Ductile Martensitic Steels

In this study the effect of thermomechanical treatment on the microstructure of austenite and martensite and the mechanical properties of a medium carbon silicon chromium spring steel with different levels of impurities is investigated. Results are presented for conventional heat treatment and for thermomechanical treatment (TMT). Compared to conventionally heat treated samples austenite deformation improves strength and ductility. Thermomechanically treated samples are not prone to embrittlement by phosphorous. TMT influences the shape and distribution of carbides within the matrix and at prior austenite grain boundaries. It is shown that utilization of TMT is beneficial for increasing the ultimate tensile strength to levels above 2200 MPa and at the same time maintaining the ductility obtained at strength levels of 1500 MPa by conventional heat treatment. The endurance limit is increased and embrittlement does not occur.

Effect of thermomechanical treatment on the structure and functional properties of a 45Ti-45Ni-10Nb alloy

The effect of quenching and high-and low-temperature thermomechanical treatments on the structural changes, the martensitic-transformation kinetics, and the functional shape recovery characteristics of a 45Ti-45Ni-10Nb alloy is studied. Electron microprobe and X-ray diffraction analyses are used to determine the structure and phase composition of the alloy and to establish the phase-transformation temperatures up to the appearance of the shape memory effect. The strains inducing the shape memory effect and providing shape recovery at temperatures above room temperature have been found. The maximum reactive stresses have been determined. Based on the studies performed, the conclusion was made that quenching and high-temperature thermomechanical treatment can provide a broad martensitic-transformation hysteresis in the alloy under study and main shape recovery on heating above room temperature. As a result, the alloy can be used as a material for thermomechanical coupling that can be stored at room temperature and is applied to the thermomechanical joint of pipelines on heating above this temperature.

Effect of thermo-mechanical treatment on the microstructure and mechanical properties of a Mg–6Gd–2Nd–0.5Zr alloy

Thermo-mechanical treatments, through combined action of cold or hot work and heat treatment, were performed on a Mg–6Gd–2Nd–0.5Zr alloy to investigate their effect on the microstructure and mechanical properties of the alloy. Cold deformation of 5 or 10% between homogenization and aging produced high density of twins and dislocations in as-quenched alloys, and caused acceleration in age-hardening response at 200 °C. Cold-deformed and peak-aged alloys exhibited higher strength and lower elongation than those of peak-aged cast alloy. Alloys subjected to hot extrusion at 450 or 350 °C showed very fine grains, and meanwhile maintained a considerable supersaturation in matrix, leading to a significant age-hardening response at 200 °C. Hot extrusion and aging brought about an overall improvement in mechanical properties, and the best combination of strength and ductility was achieved for alloy after extrusion at 350 °C and aging at 200 °C for 24 h, namely ultimate tensile strength = 381 MPa, tensile yield strength = 273 MPa and elongation = 17.6%.

Effects of Thermo-Mechanical Treatment on the Tensile and Compressive Properties of a Glass-Balloon-Dispersed Aluminum Alloy Composite

A repeated thermomechanical treatment (RTMT) was adopted to control the microstructure of a glass-balloon-dispersed aluminum alloy (AC3A) composite. The RTMT, which involves the repetition of a multi-step process and followed by heat treatment, was applied to a cast plate of the composite. The composite was successfully worked into a rod or sheet by either swaging or flat rolling. The porous glass balloons were deformed or cracked so that the composite could be worked easily. The swaged material exhibited higher tensile strength, Young’s modulus, and elongation as compared to the cast material. The composite materials also exhibited excellent energy absorption properties. [doi:10.2320/matertrans.MK200712]