Dynamic strain aging in DP steels at forming relevant strain rates and temperatures

2017-09-17
BAYRAMIN, Berkay
Simsir, Caner
Efe, Mert
Mechanical testing of dual phase (DP) steels at low strain rates (10(-3) s(-1)) have shown that they are susceptible to dynamic strain aging (DSA) between 100 degrees C-400 degrees C. During industrial forming processes at intermediate strain rates (1-10(2) s(-1)), the local temperatures may rise to the DSA range due to deformation heating which may disturb the exceptional formability of these steels. In this study, two grades of DP steel (DP590 and DP800) are tested at thermomechanical conditions relevant to forming and the effects of DSA on the formability are established. Test results show that the DSA controls the deformation between 200 degrees C-300 degrees C through serrations in the stress-strain curves of both grades. With increasing strain rates (up to 1 s(-1)) and temperatures, DSA intensifies and results in severe drops in uniform and total ductility with negative strain rate sensitivity, indicating poor formability at these conditions. A detailed analysis of the serrations coupled with dislocation density measurements by x-ray analysis suggests that the serrations can be linked to a periodic microstructural feature.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

Suggestions

Dynamic strain aging of dual phase steels in forming applications
Bayramin, Berkay; Efe, Mert; Department of Metallurgical and Materials Engineering (2017)
Sheet metals are subjected to certain temperatures (25-200oC) and strain rates (1-10 s-1) during forming applications. These thermomechanical conditions may cause dynamic strain aging (DSA) in various grades of steels including dual phase (DP) steels. DSA represent itself as serrations in the stress-strain curves. Two grades of DP steels (DP590 and DP800) were studied systematically at different strain rates (10-3s-1-1s-1) and temperatures (25oC-400oC) to investigate the DSA effects on the mechanical proper...
Microwave sintering and characterization of soft magnetic powder metallurgical Ni-Fe alloys
Erdem, Derya; Dericioğlu, Arcan Fehmi; Department of Metallurgical and Materials Engineering (2011)
In this study, prealloyed austenitic stainless steel and premixed soft magnetic Ni-Fe permalloy compacts were consolidated through microwave and conventional sintering routes at combinations of various sintering temperatures and compaction pressures. Sintered alloys were characterized in terms of their densification, microstructural evolution as well as mechanical and magnetic properties. The effect of sintering method in terms of the applied sintering parameters on the final properties of the compacts were...
Capillary boosting for enhanced heat pipe performance through bifurcation of grooves: Numerical assessment and experimental validation
Saygan, Samet; Akkus, Yigit; Dursunkaya, Zafer; Cetin, Barbaros (2022-10-01)
© 2022 Elsevier LtdIn this study, an enhanced heat pipe performance for grooved heat pipes has been demonstrated through capillary boosting with the introduction of the bifurcation of grooves. Wider grooves regularly branch to narrower grooves such that the total cross-sectional liquid flow area remains approximately the same. Following the computational framework drawn by a recently developed heat pipe analysis toolbox (H-PAT), we develop a numerical model for the heat pipes with tree-like groove architect...
The Effects of heat treatment on microstructure, hardness and fatigue behavior of (AMS5659) 15-5 precipitation hardenable stainless steel
Gören, Şahin; Gürbüz, Rıza; Department of Metallurgical and Materials Engineering (2018)
In this study, effects of heat treatment parameters on microstructure, hardness and fatigue behavior of 15-5 precipitation hardenable stainless steels have been examined. Heat treatments have been conducted in three different steps homogenization, solutionizing and aging treatment at different temperatures and times. Microstructural analysis in terms of grain size and chemical composition analysis have been performed by optical and scanning electron microscope (SEM). Then, hardness measurements were applied...
The effects of various heat treating parameters on the hardness and microstructures of the experimental 18% nickel maraging steels
Pektas, I; Atala, H (1998-01-01)
The effect of the parameters of heat treatment on the experimental 18% maraging steels was studied using hardness tester, optical, scanning electron and transmission electron microscopy and X-ray metallography techniques. The specimens were solution treated at 815, 900, 1000, 1060 degrees C for periods between 1 and 4 h. After air-cooling to room temperature. a bce martensitic structure was obtained. The higher temperature (1060 degrees C) and longer time (4 h) of the solution treatment caused essentially h...
Citation Formats
B. BAYRAMIN, C. Simsir, and M. Efe, “Dynamic strain aging in DP steels at forming relevant strain rates and temperatures,” MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, pp. 164–172, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/56761.