Papers by Keyword: Hot Deformation

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Authors: R.K. Dutta, R.M. Huizenga, M. Amirthalingam, H. Gao, A. King, M.J.M. Hermans, I.M. Richardson
Abstract: The effect of plastic deformation of austenite at elevated temperatures on the kinetics ofphase transformations during continuous cooling was studied in a high strength quenched and tem-pered structural steel S690QL1 (Fe-0.16C-0.2Si-0.87Mn-0.33Cr-0.21Mo (wt.%)) by means of in-situsynchrotron diffraction. The steel was heated to 900 C (above Ac3) in the austenite region and elon-gated by 6% followed by quenching to room temperature. Time-temperature-load resolved 2D syn-chrotron diffraction patterns were recorded and used to calculate the local d-spacings between latticeplanes. The plane specific diffraction elastic constants of austenite at 900 C in the steel were deter-mined from the local d-spacings. The effect of the deformation of austenite on the phase transforma-tion kinetics was studied. The evolution of lattice parameters and the phase fraction of the bcc phasesduring the quenching process were calculated.The calculated plane specific elastic constants of austenite at 900 C varied between 32 GPa to140 GPa for the different fhklg reflections of austenite. The deformation of austenite at 900 C re-sulted in the formation of a mixture of 38 % bainite, 59 % martensite and 3 % retained austenite afterquenching to room temperature. Without hot deformation, austenite transformed to 9 % bainite and88 % martensite with 3 % retained austenite. The presence of the bainitic and the martensitic phaseswas observed fromthe change in the slopes of the lattice parameters of the bcc phase during quenchingand confirmed by microscopy.
Authors: Jaroslaw Mizera, Julian H. Driver
Authors: Marcello Cabibbo, E. Evangelista, S. Spigarelli
Authors: Ming Yang, Yong Shun Yang, Dong Dong Yang
Abstract: Using the compression tests on a Gleeble-1500 thermo-mechanical simulator to study the dynamic recrystallization behaviours of AZ80 magnesium alloy in the temperature range of 593-683K and strain rate range of 0.01-10s-1. By the analysis of the dynamic recrystallization kinetics, the Avrami exponent (m) and the constant (k) have been determined, and they aren’t constant and depend on the dimensionless parameter(Z/A).
Authors: R. Karthikeyan, S. Ramanathan, B.C. Pai
Authors: S. Ramanathan, R. Karthikeyan, B.C. Pai
Authors: Juan Daniel Muñoz-Andrade
Abstract: ±Abstract. By applying the new quantum mechanics and relativistic mathematical model, proposed by Muñoz-Andrade, on the experimental results reported previously by Aghaie-khafri and Adhami [5], the true activation energy for hot deformation of 15-5 PH stainless steel is obtained over the temperature range of 900-1150°C and strain rates varying between 0.001 and 0.5s-1. It is interesting to contrast the results of this theoretical work with the main results of the apparent activation energy obtained for the same data, but applying the common methodology. It is shown that the true activation energy increased as the hot deformation is increased. Moreover, the true activation energy decreased as the strain rate is increased. The mean value of the true activation energy (289 kJ/mol) at high strain rate, ξ=0.5s-1, for dynamic recrystallization over the temperature range of 900-1150°C is in a closed agreement with the value of activation energy for self-diffusion in γ iron (280 kJ/mol) in dissimilarity of the result of the apparent activation energy (49221 kJ/mol) obtained beforehand by Aghaie-khafri and Adhami [5]. The results obtained in this work by the quantum mechanics and relativistic mathematical model are widely satisfactory; because essentially they are over the crucial limitations of the common methodology to obtain the activation energy at each thermo-mechanical metalworking condition. Keywords: Activation Energy, Hot Deformation, Dynamic Recrystallization, Quantum Mechanics, Special Relativity Theory.
Authors: G. Bermig, A. Bartels, H. Mecking, A. Oscarsson, W. Bevis Hutchinson
Authors: Qing Rui Wang, Ai Xue Sha, Xing Wu Li, Li Jun Huang
Abstract: The effect of strain rate and deformation temperature on flow stress of TC18 titanium alloy was studied through heat simulating tests in 760~960 with temperature interval and the strain rate interval in 0.01~10s-1. Relationship model of flow stress versus strain was established and hot deformation mechanics of TC18 titanium alloy was analyzed. The results show that the flow stress reduces obviously as the deformation temperature increases or the strain rate decreases. Dynamic recovery occurs at high strain rate above phase transformation point, while dynamic recrystallization occurs at low strain rate as well as at the temperature below phase transformation point.
Authors: Ahmad Rezaeian, Faramarz Zarandi, D.Q. Bai, Steve Yue
Abstract: The hot strip rolling of advanced microalloyed high strength steels still represents a new task to many mills due to the lack of data on the hot deformation resistance. With the aid of processing data from the Ispat-Inland hot strip mill, the “measured mean flow stresses” are calculated from the mill force using the Sims analysis and taking into account roll flattening, slip ratio and the redundant strain. A modification of the Misaka mean flow stress equation is proposed for C – Mn – Si – Al steels microalloyed with up to 0.02 % Nb. The effects of alloying and microalloying are then estimated. A new fitting parameter shows excellent agreement with the mean flow stress data from industrial processing of advanced high strength microalloyed steels. However, during the second half of the rolling schedule (lower temperature region), indications of austeniteto- ferrite transformation were found.
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