Development and validation of a processing map for Aermet100 steel
15 Feb 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 527, Iss: 4, pp 1165-1171
TL;DR: In this article, a processing map of Aermet100 steel was developed based on a simple instability condition applicable to a general flow stress versus strain rate curve at any strain and temperature.
Abstract: Using the flow stress data obtained from the compression tests in the temperature ranges of 800–1200 °C and at strain rate ranges of 0.01–50 s −1 , the processing map of Aermet100 steel was developed based on a simple instability condition applicable to a general flow stress versus strain rate curve at any strain and temperature. Deformation mechanisms in the stable and unstable regimes were verified with the microstructure observations. The optimum hot processing windows of Aermet100 steel are at temperature ranges of 1025–1200 °C and at strain rate ranges of 0.03–15 s −1 , in which dynamic recrystallization occurs with a peak efficiency of power dissipation of 38%. The instability regimes I and II occur at low temperature ranges of 800–975 °C, and at strain rate ranges of 0.1–6 s −1 and 4.5–33 s −1 , respectively. While the instability regime III occurs at high temperature ranges of 950–1200 °C and at high strain rate ranges of 15–50 s −1 . These instability regimes, whose microstructural manifestations such as cracks, shear bands and twin kink bands are detrimental to the mechanical properties of components, need to be avoided during hot processing of Aermet100 steel.
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25 May 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the experimental stress-strain data from isothermal hot compression tests on a Gleeble-3800 thermo-mechanical simulator was employed to develop the Arrhenius-type constitutive model and artificial neural network (ANN) model, and their predictability for high-temperature deformation behavior of Aermet100 steel was further evaluated.
Abstract: For predicting high-temperature deformation behaviour in Aermet100 steel, the experimental stress–strain data from isothermal hot compression tests on a Gleeble-3800 thermo-mechanical simulator, in a wide range of temperatures (1073–1473 K) and strain rates (0.01–50 s−1), were employed to develop the Arrhenius-type constitutive model and artificial neural network (ANN) model, and their predictability for high-temperature deformation behaviour of Aermet100 steel was further evaluated. The predictability of two models was quantified in terms of correlation coefficient (R) and average absolute relative error (AARE). The R and AARE for the Arrhenius-type constitutive model were found to be 0.9861 and 7.62% respectively, while the R and AARE for the feed-forward back-propagation ANN model are 0.9995 and 2.58% respectively. The breakdown of the Arrhenius-type constitutive model at the instability regimes (i.e. at 1073 K and 1173 K in 0.1, 1, 10 and 50 s−1, and at 1373 K in 50 s−1) is possibly due to that physical mechanisms in the instability regimes, where microstructure exhibits cracking, shear bands and twin kink bands, are far different from that of the stability regimes where dynamic recovery and recrystallization occur. But the feed-forward back-propagation ANN model can accurately track the experimental data across the whole hot working domain, which indicates it has good capacity to model the complex high-temperature deformation behaviour of materials associated with various interconnecting metallurgical phenomena like work hardening, dynamic recovery, dynamic recrystallization, flow instability, etc.
160 citations
TL;DR: In this paper, the deformation activation energy of extruded ZK60 magnesium alloy was investigated by compression tests in the temperature range of 250-400°C and strain rate range of 0.001-1−s−1.
87 citations
15 Jun 2011-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the activation energy map has been developed to substantiate the results obtained from the processing map and to finalize the optimum processing parameters for a modified 9Cr-1Mo steel with a wide range of temperatures (1123-1373 K) and strain rates (0.001-10 s −1 ).
Abstract: Intrinsic workability of modified 9Cr–1Mo steel has been studied in a wide range of temperatures (1123–1373 K) and strain rates (0.001–10 s −1 ). Using the experimental data obtained from isothermal hot compression tests, processing map at 0.5 true strain has been developed employing dynamic material model (DMM) approach. The activation energy map has been developed to substantiate the results obtained from processing map and to finalize the optimum processing parameters. Microstructural studies have been carried out to validate the domains of the processing map. The material shows localized deformation bands in the temperature range of 1150–1373 K at strain rates above 1 s −1 and exhibits abnormally elongated martensite laths at higher temperature (1373 K) and lower strain rates (0.001–0.01 s −1 ). The optimum domain for the hot deformation is found to be in the temperature ranges of 1250–1350 K and strain rate ranges 0.015–0.3 s −1 with a peak efficiency of 38%. In this domain, apparent activation energy is found to be 400 kJ/mol. The microstructure of the specimens deformed in this region exhibits defect free equiaxed grains.
80 citations
TL;DR: In this article, the dynamic recrystallization (DRX) behavior and hot workability of AZ41M magnesium alloy via isothermal compression experiments were studied via a Gleeble-1500D thermal-mechanical simulation machine.
74 citations
TL;DR: In this paper, an artificial neural network (ANN) model is developed to predict the hot deformation behavior of the ultra-high strength steel of Aermet100, where the inputs of the neural network are strain, strain rate and temperature, whereas flow stress is the output.
59 citations
References
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TL;DR: In this article, a new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented, which considers the workpiece as a dissipator of power in the total processing system and evaluates the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ).
Abstract: A new method of modeling material behavior which accounts for the dynamic metallurgical processes occurring during hot deformation is presented. The approach in this method is to consider the workpiece as a dissipator of power in the total processing system and to evaluate the dissipated power co-contentJ = ∫o σ e ⋅dσ from the constitutive equation relating the strain rate (e) to the flow stress (σ). The optimum processing conditions of temperature and strain rate are those corresponding to the maximum or peak inJ. It is shown thatJ is related to the strain-rate sensitivity (m) of the material and reaches a maximum value(J max) whenm = 1. The efficiency of the power dissipation(J/J max) through metallurgical processes is shown to be an index of the dynamic behavior of the material and is useful in obtaining a unique combination of temperature and strain rate for processing and also in delineating the regions of internal fracture. In this method of modeling, noa priori knowledge or evaluation of the atomistic mechanisms is required, and the method is effective even when more than one dissipation process occurs, which is particularly advantageous in the hot processing of commercial alloys having complex microstructures. This method has been applied to modeling of the behavior of Ti-6242 during hot forging. The behavior of α+ β andβ preform microstructures has been exam-ined, and the results show that the optimum condition for hot forging of these preforms is obtained at 927 °C (1200 K) and a strain rate of 1CT•3 s•1. Variations in the efficiency of dissipation with temperature and strain rate are correlated with the dynamic microstructural changes occurring in the material.
1,121 citations
15 Oct 1998-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a simple instability condition based on the Ziegler's continuum principles is developed for delineating the regions of unstable metal flow during hot deformation, which can be used for any type of the flow stress versus strain rate curve.
Abstract: A simple instability condition based on the Ziegler’s continuum principles as applied to large plastic flow, is developed for delineating the regions of unstable metal flow during hot deformation. It can be used for any type of the flow stress versus strain rate curve. This criterion has been validated using the flow stress data of IN 718 with microstructural observations. The optimum hot working conditions for the superalloy IN 718 are suggested based on the instability map.
200 citations
15 Mar 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the hot deformation behavior of Mg-3Al alloy has been studied using the processing-map technique and various domains in the map corresponding to different dissipative characteristics have been identified as follows: (i) grain boundary sliding (GBS) domain accommodated by slip controlled by grain boundary diffusion at slow strain-rates ( −3 ǫs −1 ) in the temperature range from 350 to 450
Abstract: The hot deformation behaviour of Mg–3Al alloy has been studied using the processing-map technique. Compression tests were conducted in the temperature range 250–550 °C and strain rate range 3 × 10 −4 to 10 2 s −1 and the flow stress data obtained from the tests were used to develop the processing map. The various domains in the map corresponding to different dissipative characteristics have been identified as follows: (i) grain boundary sliding (GBS) domain accommodated by slip controlled by grain boundary diffusion at slow strain-rates ( −3 s −1 ) in the temperature range from 350 to 450 °C, (ii) two different dynamic recrystallization (DRX) domains with a peak efficiency of 42% at 550 °C/10 −1 s −1 and 425 °C/10 2 s −1 governed by stress-assisted cross-slip and thermally activated climb as the respective rate controlling mechanisms and (iii) dynamic recovery (DRV) domain below 300 °C in the intermediate strain rate range from 3 × 10 −2 to 3 × 10 −1 s −1 . The regimes of flow instability have also been delineated in the processing map using an instability criterion. Adiabatic shear banding at higher strain rates (>10 1 s −1 ) and solute drag by substitutional Al atoms at intermediate strain rates (3 × 10 −2 to 3 × 10 −1 s −1 ) in the temperature range (350–450 °C) are responsible for flow instability. The relevance of these mechanisms with reference to hot working practice of the material has been indicated. The processing maps of Mg–3Al alloy and as-cast Mg have been compared qualitatively to elucidate the effect of alloying with aluminum on the deformation behaviour of magnesium.
199 citations
TL;DR: In this paper, the authors have shown that shear deformation twins and microbands are also precursors to deformation deformation faults in alloys and alloys with high stacking-fault free energy.
Abstract: Plane-wave shock deformation has been shown to produce deformation twins or twin-faults in essentially all metal and alloys. In FCC metals and alloys twinning depends upon stacking-fault free energy (SFE) and a critical twinning pressure; which increases with increasing SFE. For impact cratering where the shock wave is spherical and a prominent deviatoric (shear) stress is involved, metals and alloys with high SFE form microbands coincident with {111} plane traces while low SFE metals and alloys either form mixtures of twins and microbands or microtwins. Oblique shock loading of copper also produces mixtures of twins and microbands. Both microtwins and microbands increase in volume fraction with increasing grain size. BCC iron is observed to twin in both shock loading and as a result of impact cratering. Impact craters, shaped charges, and other examples of extreme deformation and flow at high strain rates exhibit various regimes of shear bands and dynamic recrystallization as a mechanism for solid-state flow. Deformation twins and microbands are also often precursors to this process as well. Examples of these phenomena in FCC materials such as Al, Ni, Cu, stainless steel and brass, and BCC materials such as Fe, W, Mo, W-Ta, and Ta are presented; with emphasis on optical metallography and transmission electron microscopy.
123 citations