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In this work, the effects of dynamic strain aging and dynamic recovery on metal flow during warm working are studied. Compression experiments are utilized to assess the flow behavior of a low carbon steel under warm deformation conditions. Then, a two dimensional finite element routine is coupled with dynamic recovery and dynamic strain aging models. In this way, the temperature and the velocity fields are predicted during warm working operations with regard to the effects of dynamic recovery and dynamic strain aging. Warm rolling tests are performed in order to verify the modelling results. Comparison between the predicted and measured roll forces shows reliability of the employed model  

In this study, strain ageing during and after warm rolling of a carbon steel has been investigated. At the first step, the occurrence of serrated flow was studied by means of tensile tests at different temperatures and strain rates. In the next stage, warm rolling experiments were performed under different rolling conditions and then the samples were aged at the room temperature for a period of 3 months. For both aged and non-aged samples, tensile tests were employed to evaluate their mechanical properties. The results show that static strain ageing is possible to happen in the utilized ageing period and increases the yield stress of the aged steel. However, the samples that experience both... 

Dynamic strain ageing may occur during warm working of low carbon steels and causes significant changes in flow behaviour and microstructure of the deformed material. Therefore, for a proper designing of an industrial forming process performing under warm deformation conditions, the effect of dynamic strain aging should be taken into account. The aim of this investigation is to predict the velocity and the temperature fields within the rolling metal with regard to the dynamic strain aging. For this purpose, compression tests at various temperatures and strain rates have been conducted to evaluate dynamic strain aging in a low carbon steel. Then, by coupling the experimental results with a... 

In this study, effect of rolling speed on strain aging phenomena in warm rolling of a carbon steel has been investigated. For this purpose, by using a mathematical model and predicting temperature and strain rate fields, the possibility of occurrence of dynamic strain aging during the warm rolling was first evaluated. In the next stage, warm-rolled samples were aged up to 11 months at room temperature for studying the kinetics of static strain aging, while mechanical tests as well as microstructural evolutions have been performed to determine the effect of strain aging on material behavior. The results indicate that dynamic strain aging may not occur for the employed rolling program;... 

In this study, a multistage strain aging method that used rolling pre-strain (compression) was developed to study the effects of temperature, and inter-pass time on static strain aging behavior of low carbon steel. An increase in hardness and strength caused by work hardening due to the forming process and aging at every stage of aging that is calculated separately. To comparing the effects of multistage aging against typical strain aging, the samples were rolled and subjected to the aging process both exist in typical one-stage aging that setting a 20% rolling pre-strain and in multiple stages pre-strain by setting a 5% rolling ratio in four stages. The mechanical properties of aged samples... 

A 0.15% C-1.2% Si-1.7% Mn steel was intercritically annealed at 780 °C for 5 min and then isothermally held at 400 °C for 4 min followed by oil quenching to room temperature and the annealed microstructure consist of 75% ferrite, 15% bainite and 10% retained austenite was produced. Samples of this steel with triple phase structure were tensile tested at temperature range of 25-450 °C. Stress-strain curves showed serration flow at temperature range of 120-400 °C and smooth flow at the other temperatures. All of the stress-strain curves showed discontinuous yielding at all testing temperatures. Both yield and ultimate tensile strength decreased with increasing temperature, but there exists a... 

An investigation was performed on the static strain aging behavior of warm-rolled low carbon steel during a nearly 1-year aging period, from the view point concerning with influence of changing the deformation speed and cooling media. Mechanical response of the examined material during aging period was evaluated through variations occurred in strength and hardness of the warm-deformed steel. It was shown that changing the rolling speed as well as cooling rate, may result in the occurrence of different metallurgical phenomena, consequently altering the aging kinetics of the material. It was also found that by increasing rolling speed, an increase in the value of hardness and UTS takes place,... 

Flow behavior of two grades of steel including a high silicon (HS) steel and a plain low carbon steel as the reference were considered in this work. Tensile testing at temperatures varying between 25 and 550 °C and different strain rates in the range of 4×10-5 to 0.1 s-1 were conducted and the mechanical properties, such as elongation at fracture point and strain rate sensitivity were then determined. It is observed that for both steels, dynamic strain aging occurs in the employed deformation conditions, however, the region of serrated flow and the type of the serration were somehow different. For the case of the HS steel, the serrated flow region is shifted to the higher temperatures and... 

Dual phase steels with different martensite volume fraction and morphology were tensile tested at temperature range of 25-550 °C. Stress-strain curves of all steels showed serration flow at temperature range of 250-450 °C and smooth flow at the other temperatures. Both yield and ultimate tensile strengths increased with increasing testing temperature up to about 450 °C and then decreased at higher temperatures. At a given temperature, yield stress, tensile strength, and work hardening increased with increasing volume fraction of martensite. Similar behavior was observed by changing martensite morphology from network to fibrous martensite. The change in mechanical properties was related to... 

In this study both the quench aging and static strain aging kinetics of a 6082 Al alloy were investigated at a temperature range of 130-200°C using the Vickers hardness and tensile test. The activation energy and dislocation density were determined at different stages of the aging phenomenon. The former was used to analyse the kinetics of aging and the latter to interpret the competition of strengthening and recovery mechanisms during aging. It is shown that different activation energies are achieved depending on the aging time and temperature relating to formation of appropriate precipitates at different stages of aging. Moreover, it is revealed that prestrain reduces the activation energy.... 

In this study, the effect of strain ageing on mechanical properties of warm-rolled steel is investigated. Warm-rolling experiments together with mechanical testing are employed to investigate the effect of processing parameters on the ageing kinetics during and after warm rolling of a low-carbon steel. To do so, the occurrence of dynamic strain ageing is first determined by means of a two-dimensional thermo-mechanical model and then the effect of this phenomenon on the subsequent static strain ageing after warm rolling is studied employing mechanical testing. The results show that the occurrence of dynamic strain ageing during warm rolling may effectively alter the progress of the subsequent... 

The influence of equal channel angular pressing (ECAP) on microstructure and mechanical behavior, as well as, strain aging during ECAP and post-ECAP of Mg-1.8Zn-0.7Si-0.4Ca biomedical alloy was examined. The alloy in solid solution heat-treated condition was processed by ECAP with route BC at 350 and 400 °C. The specimens ECAPed at 350 °C were aged at 125 and 150 °C for different times. The hardness and shear punch test results indicated that performing ECAP at 350 °C for 4 passes increases the hardness and shear strength of the alloy from 48 HV and 110 MPa to 71 HV and 188 MPa, respectively. It was revealed that the average grain size of the alloy decreases from 78 µm to about 3 µm after 4... 

In this paper, dynamic strain aging (DSA) behavior in a temperature range of (25-235°C) and strain rate range of (10-4-5×10-2s-1) was investigated using a supersaturated age hardenable aluminum alloy. It was found that two mechanisms consisted of pinning of solute atoms to mobile dislocations and dynamic precipitation, were responsible for DSA in the testing conditions. The effects of both mechanisms on the macroscopic flow curve were studied using experimental and improved physically based material modeling approaches. It was shown that both phenomena lead to a negative strain rate hardening in the alloy. Dynamic precipitation acting at high temperature results in considerable work... 

A new integrated physically based constitutive model was developed for an age hardenable Al- Mg-Si alloy. The kinetics of precipitation during various stages of aging was modelled. The precipitate features consisted of particle radius and volume fraction obtained from the kinetics model, which was used to compute the alloy yield strength/hardness. A published multiinternal variable workhardening model was improved to take into account the effects of solute solution and precipitates on the alloy hardening capacity after performing different cycles of aging treatment. The flow curves and hardness predicted by the model were in good agreement with the experimental results. The model is able to... 

Effect of deformation path change on the static strain aging of low carbon steel was studied in this work. In the first stage, strip samples were subjected to cold rolling processes under different paths with the same total reduction in thickness while the deformation behaviors of the rolled samples were also evaluated using a mathematical analysis. Then, cold-rolled strips were aged in room temperature up to 45 days while hardness and tensile evaluations were performed to assess the mechanical properties of the as-rolled and the aged samples. Finally, the influence of rolling pass schedule on the subsequent strain aging phenomenon was investigated by means of the experimental results and...