Hot compressive flow stress modeling of homogenized AZ61 Mg alloy using strain-dependent constitutive equations

Wu, Horng-yu; Yang, Jyh Bin; Zhu, Feng-Jun; Wu, Chung Hsien

doi:10.1016/j.msea.2013.03.005

Cited by 42 publications

(17 citation statements)

References 27 publications

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“…With the information obtained from the processing map, the guideline for optimizing hot processing parameters can be determined, and the damage processes and instability processed can be avoided. The processing maps have been widely investigated in the production of titanium alloys [3], magnesium alloys [4,5], aluminium alloys [6], nickel alloys [7] and steels [8,9]. 30Cr2Ni4MoV steel has attracted extensive attention for its good properties in terms of strength, toughness and wear resistance, and has been widely used in the production of an ultra-super-critical power cycle generator.…”

Section: Introductionmentioning

confidence: 99%

Hot Deformation Behavior of As-Cast 30Cr2Ni4MoV Steel Using Processing Maps

Zhou

2017

Metals

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The hot deformation behavior of as-cast 30Cr2Ni4MoV steel was characterized using processing maps in the temperature range 850 to 1200 • C and strain rate range 0.01 to 10 s −1 . Based on the obtained flow curves, the power dissipation maps at different strains were developed and the effect of the strain on the efficiency of power dissipation was discussed in detail. The processing maps at different strains were obtained by superimposing the instability maps on the power dissipation maps. According to the processing map and the metallographic observation, the optimum domain of hot deformation was in the temperature range of 950-1200 • C and strain rate range of 0.03-0.5 s −1 , with a peak efficiency of 0.41 at 1100 • C and 0.25 s −1 which were the optimum hot working parameters.Metals 2017, 7, 50 2 of 12 2. Experimental Procedure Hot Deformation TestsThe composition of the 30Cr2Ni4MoV steel used in this research, which was directly sampled from 600 t ingot, with a composition of 0.28C-0.02Mn-0.01Si-0.003P-0.003S-1.72Cr-0.41Mo-3.63Ni-0.11V-(bal.)Fe, and all values given in wt %. The steel was machined into cylindrical specimens which were 12 mm in height and 8 mm in diameter. One-hit isothermal compression tests were performed on a Gleeble-1500 thermal mechanical simulation tester (Dynamic Systems Inc., Poestenkill, NY, USA) in Tsinghua University. In order to reduce frictional effects during compression and avoid the sticking problem in quenching, the Ta pieces with a thickness of 0.5 mm were positioned between the anvils and the specimens. The specimens were firstly preheated at 1200 • C for 5 min to obtain the same initial grain size and homogeneous microstructure before compression [13]. After the structure uniformity, they were then cooled to the test deformation temperature at 10 • C/s and held for 1 min prior to deformation for the purpose of temperature gradient elimination. Deformation temperature ranging from 850 • C to 1200 • C in increments of 50 • C were chosen for these compression tests. A deformation of strain ε = 0.7 was applied at strain rates ranging from 0.01 s −1 to 10 s −1 , which was followed by water quenching to preserve the deformed austenite microstructure for metallographic observation. The polished surfaces were etched using a saturation picric acid for 7 min water bath heating at 70 • C. All optical micrographs were obtained from the center of the longitudinal sections of the specimens and the original grain size after soaking at 1200 • C for 5 min was 266.1 µm. Processing Map EstablishmentThe processing map is generated using data of flow stress as a function of temperature and strain rate over a wide range obtained from the hot compression test based on the theory of DMM [1,2,14,15]. According to the DMM, the workpiece essentially dissipates power during hot deformation, which may be represented as a sum of two complementary parts: G and J [1,2]. The G represents the power dissipated by plastic deformation, most of which is converted into viscoplastic heat and the rest is stored as ...

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Section: Introductionmentioning

confidence: 99%

Hot Deformation Behavior of As-Cast 30Cr2Ni4MoV Steel Using Processing Maps

Zhou

2017

Metals

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“…where σ m,i is measured stress, σ c,i is calculated stress, n is number of observed points of stress-strain curve and i-specific point on curve. The same measure 3is also used by many other authors [4][5][6][7][21][22][23].…”

Section: Modeling Using Transfer Functions and Model Accuracy Estimatmentioning

confidence: 99%

Description of Hot Compressive Stress-Strain Curves Using Transfer Functions

Vode

Malej

Arh

et al. 2019

Metals

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Mathematical descriptions of true stress/true strain curves, experimentally obtained on cylindrical specimens under hot compressive conditions, are of great importance and are widely investigated. An additional black-box modelling approach using transfer functions (TF) is tested. For tested 51CrV4 steel, a TF of third order is employed for description of true stress (output) depending on the strain rate (input). Sets of TF coefficients are determined using numerical optimization techniques for each testing temperature and strain rate. To avoid scattering of TF parameters, time in Laplacian transformation is replaced with strain, while TF input is the strain rate. Obtained models cover deformations starting practically from zero to 0.7. Average absolute relative error for models based on TF of the third order and of the second order are 0.93% and 3.64%.

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“…To evaluate the accuracy of the constitutive equation, the absolute relative error (E) between the calculated flow stress and the experimental flow stress given by Eq. (9) [18,29,30] was calculated at each strain, and averages over all the strains were calculated, (9) where σ e is the experimental flow stress, σ c is the calculated flow stress, and N is the number of data points at each strain.…”

Section: Constitutive Analysis Following the Standard Proceduresmentioning

confidence: 99%

Constitutive modeling and understanding of the hot compressive deformation of Mg–9.5Zn–2.0Y magnesium alloy with reduced number of strain-dependent constitutive parameters

Kim

Kwak

2017

Met. Mater. Int.

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The hot compressive flow behavior of the cast Mg-9.5Zn-2.0Y alloy as a function of strain was analyzed, and the degree of dependence of the parameters (A: material constant, n2: stress exponent, Qc: activation energy for plastic flow and : stress multiplier) of the constitutive equation ( ) upon the strain was examined in a systematic manner. This is to explore the possibility of representing the hot compressive deformation behavior of metallic alloys in a simple way by using a reduced number of strain-dependent constitutive parameters. The analysis results for several different cases can be interpreted as follows: (1) Qc can be treated as being strain-independent, which is physically sensible; (2) while only the microstructure changes as a function of strain at low flow stresses, as the flow stress increases, the power-law creep deformation and power-law breakdown mechanisms change; (3) the regime where only A is strain dependent expanded to higher strain rates and lower temperatures as the strain increased, suggesting that the number of the straindependent parameters decreases as the initial microstructure is refined by dynamic recrystallization, and the microstructure approaches a steady state.

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Hot compressive flow stress modeling of homogenized AZ61 Mg alloy using strain-dependent constitutive equations

Cited by 42 publications

References 27 publications

Hot Deformation Behavior of As-Cast 30Cr2Ni4MoV Steel Using Processing Maps

Hot Deformation Behavior of As-Cast 30Cr2Ni4MoV Steel Using Processing Maps

Description of Hot Compressive Stress-Strain Curves Using Transfer Functions

Constitutive modeling and understanding of the hot compressive deformation of Mg–9.5Zn–2.0Y magnesium alloy with reduced number of strain-dependent constitutive parameters

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