Processing map and dynamic recrystallization behaviours of 316LN-Mn austenitic stainless steel

The hot deformation behaviours of 316LN-Mn austenitic stainless steel were investigated by uniaxial isothermal compression tests at different temperatures and strain rates.The microstructural evolutions were also studied using electron backscatter diffraction.The flow stress decreases with the increasing temperature and decreasing strain rate.A constitutive equation was established to characterize the relationship among the deformation parameters,and the deformation activation energy was calculated to be 497.92 k J/mol.Processing maps were constructed to describe the appropriate processing window,and the optimum processing parameters were determined at a temperature of 1107-1160℃ and a strain rate of 0.005-0.026 s^(-1).Experimental results showed that the main nucleation mechanism is discontinuous dynamic recrystallization(DDRX),followed by continuous dynamic recrystallization(CDRX).In addition,the formation of twin boundaries facilitated the nucleation of dynamic recrystallization.

Processing map for hot working of SiC_p/7075 Al composites

The hot deformation behaviour of 7075 aluminium alloy reinforced with 10%of SiC particles was studied by employing both"processing maps"and microstructural observations.The composite was characterized by employing optical microscope to evaluate the microstructural transformations and instability phenomena.The material investigated was deformed by compression in the temperature and strain rate ranges of 300-500℃and 0.001-1.0 s-1,respectively.The deformation efficiency was calculated by strain rate sensitivity(m)values obtained by hot compression tests.The power dissipation efficiency and instability parameters were evaluated and processing maps were constructed for strain of 0.5.The optimum domains and instability zone were obtained for the composites.The optimum processing conditions are obtained in the strain rate range of 0.1-0.9 s-1and temperature range of 390-440 ℃with the efficiency of 30%.

Constitutive modeling of flow behavior and processing maps of Mg-8.1 Gd-4.5Y-0.3Zr alloy

High temperature deformation behavior and workability of Mg-8.1 Gd-4.5Y-0.3Zr alloy were studied by compression tests.Arrhenius equation with strain compensation and processing maps were established.The results show that the activation energy Q,structure factor a,n and In A varies with the strain,its relationship fit well by fifth order polynomial.The flow stresses predicted by the extracted model are in good agreement with the experimental results.There are five typical domains in the processing map,and the deformation mechanisms in different domains were determined by microstructure analysis.The feasible processing window of the alloy is in the areas of 400-500℃/0.001-0.1 s^(-1).

Constitutive behavior and processing maps of a new wrought magnesium alloy ZE20 (Mg-2Zn-0.2Ce)

ZE20(Mg-2Zn-0.2Ce)^2 is a new wrought magnesium alloy with improved extrudability and mechanical properties[1].To understand the constitutive behavior and workability of this new alloy,Gleeble thermomechanical testing has been carried out in this study.The flow stress behavior of ZE20 was investigated between 250℃–450℃ and 10^–3 s^–1–1.0 s^–1 in isothermal compression.Constitutive descriptions of the flow stress are provided.A new general approach at application of the extended Ludwik equation is demonstrated and was found to be more accurate than the hyperbolic sine Arrhenius model while having a similar number of model constants.Processing maps were developed based on the experimental results and are verified with microstructural investigation.A region of safe processing with non-basal texture and high activity of dynamic recrystallization(DRX)was found between 375℃ and 450℃,from 10^–1 s^–1 to 10^–2.5 s^–1.A region of potentially safe processing with annealing that is associated with shear band nucleation of non-basal grains was identified for temperatures as low as 300℃ and rates as high as 10^–1 s^–1.

Optimization of TC11 alloy forging parameters using processing maps

Isothermal compression of TC11 alloy at the deformation temperatures ranging from 1023 to 1323 K with an interval of 20 K, the strain rates of 0.001, 0.1, 1.0, and 10.0 s-1, and the height reductions of 50% and 70% was conducted on a Gleeble-1500D thermomechanical simulator. According to the experimental results, the isothermal compression and the processing maps of TC11 alloy at different strains were drawn by using the dynamic material model （DMM）. Based on the processing maps, the proper forging parameters, including a combination of defor-mation temperature and strain rate, vary with the strain in different phases of TC11 alloy.

Processing Map of C71500 Copper-nickel Alloy and Application in Production Practice

The isothermal compression tests of C71500 copper-nickel alloy at different temperatures (1 073-1 273 K) and strain rates (0.01-10 s^-1) were carried out on Gleeble-3500 thermo-mechanical simulator.The real stress-strain data were obtained.On the basis of dynamic material model,the power dissipation was established.The peak efficiency of the power dissipation is 57%.At the same time,Prasad’s,Murty’s and Babu’s instability criteria based on Ziegler’s expectant rheology theory,and Gegel’s and Malas’s instability criteria based on Lyaponov’s function theory,were used to predict the unstable regions in the processing map.The maximum entropy generation rate and large plastic deformation principle are more in line with the hot deformation process of C71500 alloy,so the accuracy of Prasad’s instability criterion is much better.According to the obtained macro-crack and micro-metallographic structure morphologies,the temperature range of 1 098-1 156 K and the strain rate range of 2.91-10 s^-1,and the temperature range of 1 171-1 273 K and the strain rate range of 0.01-0.33 s^-1 are more suitable for the processing area of C71500 alloy.The accuracy of the above conclusions were verified by the forging of materials and the analysis of hot piercing tubes.The significance of this paper is to provide theoretical basis and technological conditions for hot-press processing of C71500 alloy.

Hot deformation behavior of uniform fine-grained GH4720Li alloy based on its processing map

The hot deformation behavior of uniform fine-grained GH4720Li alloy was studied in the temperature range from 1040 to 1130℃ and the strain-rate range from 0.005 to 0.5 s-1 using hot compression testing. Processing maps were constructed on the basis of compression data and a dynamic materials model. Considerable flow softening associated with superplasticity was observed at strain rates of 0.01 s 1 or lower. According to the processing map and observations of the microstructure, the uniform fine-grained microstructure remains intact at 1100℃ or lower because of easily activated dynamic recrystallization （DRX）, whereas obvious grain growth is observed at 1130℃. Metal- lurgical instabilities in the form of non-uniform microstrucmres under higher and lower Zener-Hollomon parameters are induced by local plastic flow and primary γ＇ local faster dissolution, respectively. The optimum processing conditions at all of the investigated strains are pro- posed as 1090-1130℃ with 0.084）.5 s-1 and 0.0054）.008 s-1 and 1040-1085℃ with 0.0054）.06 s-1.

Comparative study on high temperature deformation behavior and processing maps of Mg-4Zn-1RE-0.5Zr alloy with and without in-situ sub-micron sized TiB2 reinforcement

Mg-4Zn-1RE-0.5Zr (ZE41) Mg alloy is extensively used in the aerospace and automobile industries.In order to improve the applicability and performance,this alloy was engineered with in-situ Ti B2reinforcement to form Ti B2/ZE41 composite.The high temperature deformation behavior and manufacturability of the newly developed Ti B2/ZE41 composite and the parent ZE41 Mg alloy were studied via establishing constitutive modeling of flow stress,deformation activation energy and processing map over a temperature range of 250℃-450℃ and strain rate range of 0.001 s-1-10 s-1.The predicted flow stress behavior of both materials were found to be well consistent with the experimental values.A significant improvement in activation energy was found in Ti B2/ZE41 composite (171.54 k J/mol) as compared to the ZE41 alloy (148.15 k J/mol) due to the dispersed strengthening of in-situ Ti B2particles.The processing maps were developed via dynamic material modeling.A wider workability domain and higher peak efficiency (45%) were observed in Ti B2/ZE41 composite as compared to ZE41 alloy (41%).The Dynamic recrystallization is found to be the dominating deformation mechanism for both materials;however,particle stimulated nucleation was found to be an additional mode of deformation in Ti B2/ZE41 composite.The twinning and stress induced cracks were observed in both the materials at low temperature and high strain rate.A narrow range of instability zone is found in the present Ti B2/ZE41 composite among the existing published literature on Mg based composites.The detailed microstructural characterization was carried out in both workability and instability domains to establish the governing deformation mechanisms.

Flow Stress Behavior and Processing Map of Al-Cu-Mg-Ag Alloy during Hot Compression

The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s^-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.

Hot Deformation Behavior and Processing Maps of As-cast Mn18Cr18N Steel

Hot deformation behavior of as-cast Mn18Cr18 N austenitic stainless steel was studied in the temperature range of 950-1200 ℃ and strain rate range of 0.001-1 s^（-1） using isothermal hot compression tests. The true stress-strain curves of the steel were characterized by hardening and subsequent softening and varied with temperatures and strain rates. The hot deformation activation energy of the steel was calculated to be 657.4 k J/mol, which was higher than that of the corresponding wrought steel due to its as-cast coarse columnar grains and heterogeneous structure. Hot processing maps were developed at different plastic strains, which exhibited two domains with peak power dissipation efficiencies at 1150 ℃/0.001 s^（-1） and 1200 ℃/1 s^（-1）, respectively. The corresponding microstructures were analyzed by optical microscopy（OM）, scanning electron microscopy（SEM）, and electron backscatter diffraction（EBSD）. It has been confirmed that dynamic recrystallization（DRX） controlled by dislocation slipping and climbing mechanism occurs in the temperature and strain rate range of 1050-1200 ℃ and 0.001-0.01 s^（-1）; And DRX controlled by twinning mechanism occurs in the temperature and strain rate range of 1100-1200 ℃, 0.1-1 s^（-1）. These two DRX domains can serve as the hot working windows of the as-cast steel at lower strain rates and at higher strain rates, respectively. The processing maps at different strains also exhibit that the instability region decreases with increasing strain. The corresponding microstructures and the less tensile ductility in the instability region imply that the flow instability is attributed to flow localization accelerated by a few layers of very fine recrystallized grains along the original grain boundaries.

Study on Hot Deformation Cracks of Steel D2 Using Processing Map

The hot deformation behaviors of steel D2 in the range of 900 ℃ to 1 160 ℃ and strain rate range of 0.01 s -1 to 10 s -1 have been studied by using Processing Map developed on the basis of dynamic materials model. The efficiency of energy dissipation η is taken as a function of temperature and strain rate to obtain a Processing Map. In the Processing Map of steel D2, there are two zones of cracking susceptivity with high dissipation efficiency η of 46 % and 63 % respectively. One zone is in the range of 900 ℃ to 980 ℃ and the strain rate range of 0.01 s -1 to 0.06 s -1 , and the other from 1 140 ℃ to 1 160 ℃ and 8 s -1 to 10 s -1 . The experiment proves that there are microstructural brittle transgranular fractures and macroscopic thermal cracks in the two zones respectively. The map also revealed that deformation in these two zones is of instable flowing , so these two zones should be avoided when choosing hot deformation conditions.

On hot deformation behavior and workability characteristic of 42CrMo4 steel based on microstructure and processing map

In order to determine the safe region of 42CrMo4 steel during hot working and obtain excellent workability,the hot deformation behavior at the temperatures of 850-1150℃and the strain rates of 0.01-10 s^(-1)was investigated through single-pass compression test of thermo-simulation.Through observing and analyzing the true stress-strain curves,the conclusion may be drawn that the flow stress value increases with the decrease in deformation temperature and the increase in strain rate.Raising temperature and reducing strain rate are conductive to dynamic recrystallization(DRX)nucleating and growing,but adiabatic heating caused by higher strain rate can also promote it.Since the Zener-Hollomon(Z)value and dynamic recrystallized grain size(D_(DRX))have completely opposite trends with deformation condition parameters,the expression of Z value and DDRX can be determined as:D_(DRx)=15,567.645Z^(-02174).The processing map and instability map constructed at a strain of 0.9 show that the suitable window for hot working with a true strain of 0.9 is in the temperature range of 970-1150℃and strain rate range of 0.01-0.25 s^(-1),as well as at the temperature of 1150℃ and strain rate range of 0.25-10 s^(-1).The instability phenomenon appears in the process interval of 850-1096℃ and 0.22-10 s^(-1).

Thermal Deformation Behavior and Processing Map of a Novel CrFeNiSi_(0.15)Medium Entropy Alloy

The thermal deformation behavior of a novel CrFeNiSi_(0.15)medium entropy alloy(MEA)was studied via isothermal compression experiments,with the processing parameter range of 900–1200℃and 0.001–1 s^(−1).According to experimental data,the modified constitutive equation had been obtained,which precisely predicted the flow behavior of CrFeNiSi_(0.15)MEA during thermal deformation.At the same time,the processing map was established on the basis of the dynamic material model(DMM)theory.According to the map,the optimal processing parameters were determined at 1130–1200℃/0.06–1 s−1,under which the power dissipation efficiency could reach above 34%.The peak efficiency was above 38%,which occurred at 1200℃/1 s^(−1).In such parameter,complete dynamic recrystallization(DRX)also occurred.The flow instability of CrFeNiSi_(0.15)MEA was estimated to occur at 900–985℃/0.12–1 s^(−1),which was shown as grain boundaries cracking.Furthermore,both the continuous DRX(CDRX)and discontinuous DRX(DDRX)occurred simultaneously during thermal deformation.Meanwhile,some twins were also newly formed during DRX process,most of which were primary twins.The occurrence of twinning was beneficial to promote the development of DRX behavior.

Processing map of as-cast 7075 aluminum alloy for hot working

The true stress-strain curves of as-cast 7075 aluminum alloy have been obtained by isothermal compression tests at temperatures of 300 500 ~C and strain rates of 0.01 10 s i. The plastic flow instability map is established based on Gegel B and Murthy instability criteria because the deformed compression samples suggest that the combination of the above two instability criteria has more comprehensive crack prediction ability. And the processing map based on Dynamic Mate- rial Model （DMM） of as-cast 7075 aluminum alloy has been developed through a superposition of the established instability map and power dissipation map. In terms of microstructure of the deformed samples and whether plastic flow is stable or not, the processing map can be divided into five areas： stable area with as-cast grain, stable area with homogeneous grain resulting from dynamic recovery, instability area with as-cast grain, instability area with the second phase and instability area with mixed grains. In consideration of microstructure characteristics in the above five areas of the processing map, the stable area with homogeneous grain resulting from dynamic recovery, namely the temperatures at 425465 ℃ and the strain rates at 0.01^-1 s^-1, is suggested to be suitable processing window for the as-cast 7075 aluminum alloy.

Flow behavior and processing map for hot deformation of ATI425 titanium alloy

Flow behavior and processing map play important roles in the hot deformation process of titanium alloys. In this research, compression Gleeble tests have been carried out to investigate the stress-strain relationship at temperatures ranging from 700 to 1000 ℃ and strain rates ranging from 0.001 to 1 s-1 for ATI 425 titanium alloy. Arrhenius type constitutive equation was obtained to describe the compressive flow behavior with modification of additional deformation dead zone, friction model, temperature model and strain rate. The introduction of novel calculation method for α value in Arrhenius equation gives more accurate fitting than traditional one. Processing maps were drawn based on the distribution of dissipator co-content, and optimized deformation temperature and strain rate range obtained. It is proven to be accurate and effective through the experimental results. The microstructure analysis shows that more dynamic recrystallization can be achieved in the area with larger ηvalue on the processing map.

3D processing map for hot working of extruded AZ80 magnesium alloy

The hot deformation behavior of extruded AZ80 magnesium alloy was investigated using compression tests in the temperature range of 250–400 °C and strain rate range of 0.001–1.000 s–1. The 3D power dissipation map was developed to evaluate the hot deformation mechanisms and determine the optimal processing parameters. Two domains of dynamic recrystallization were identified from the 3D power dissipation map, with one occurring in the temperature and strain rate range of 250–320 °C and 0.001–0.010 s–1and the other one occurring in the temperature and strain rate range of 380–400 °C and 0.001–0.003 s–1. In order to delineate the regions of flow instability, Prasad’s instability criterion, Murty’s instability criterion and Gegel’s stability criteria were employed to develop the 3D instability maps. Through microstructural examination, it is found that Prasad’s and Murty’s instability criteria are more effective than Gegel’s stability criteria in predicting the flow instability regions for extruded AZ80 alloy. Further, the 3D processing maps were integrated into finite element simulation and the predictions of the simulation are in good agreement with the experimental results.

Hot deformation behavior and process parameter optimization of Ti22Al25Nb using processing map

The hot deformation behavior of Ti22A125 Nb was investigated by hot compression test.The flow stressstrain curves can be divided into two types：conventional dynamic recrystallization（DRX） and discontinuous DRX.The different softening mechanism and micro structure observation of conventional DRX and discontinuous DRX were analyzed.The processing map（PM） of Ti22A125 Nb was built to predict the safe deformation region.The optimal low strain rate domain（DOM I） with high power dissipation efficiency indicates the complete DRX.Additionally,in the high strain rate and low-temperature domain（DOM Ⅲ）,the power dissipation efficiency is low and some adiabatic shear bands and glide bands are observed,which are unsafe and should be avoided.Finally,the DRX map was established.In DOM I,it reveals low dislocation density and high DRX content,which is in agreement with PM.

Hot deformation behavior and processing map of low-alloy offshore steel

The hot deformation behavior of a low-alloy offshore steel was systematically investigated within the temperature range of 850-1150℃ and strain rate range of 0.01-10 s^(-1),via hot compression testing.The hot working equation,grain size model and recrystallization kinetic models of the steel were developed by fitting the experimental data.The results show that the decrease in Zener-Hollomon Z-parameter value(the increase in deformation temperature and the decrease in strain rate)is beneficial for the occurrence of dynamic recrystallization,and the grain size can be refined by increasing the Z-parameter value within the deformation range of dynamic recrystallization.However,when the Z-parameter value is higher than 3.43×10^(16),dynamic recrystallization will be difficult to occur within the range of experimental deformation conditions.Additionally,processing maps at different strains were constructed.According to the processing map and microstructural analysis,the optimal hot working conditions of the studied steel are within the temperature range of 1000-1100℃ and strain rate range of 0.1-1 s^(−1),and a complete recrystallization microstructure with fine homogeneous grains could be obtained.

Effect of Precipitation on Hot Deformation Behavior and Processing Maps of Nickel-Base UNS N10276 Alloy

The hot deformation characteristics and processing maps of aged nickel-base UNS N10276 alloy were inves- tigated and compared with those of solution-treated UNS N10276 alloy at temperatures of 950-1250 ℃ and strain rates between 0.01 and 10 s-1. The dominant precipitated phase in the aged alloy was identified as topologically close-packed （TCP） # phase enriched in Mo and Ni. The precipitates present in the UNS N10276 alloy could significantly facilitate flow softening after peak stress at temperatures lower than 1150 ℃ and strain rates higher than 0.01 s-1. Processing maps at true strains of 0.1-0.9 were developed using the dynamic materials model and experimental flow stress data. Although aging treatment slightly shrank the suitable hot working window of this alloy, the aged alloy showed higher peak efficiencies of power dissipation and smaller unstable regions in comparison with solution-treated alloy. Furthermore, aging treatment eliminated the instability region of processing maps at true strains of 0.2-0.5. The precipitated phase promoted dynamic recrystallization （DRX） by the particle-stimulated nucleation （PSN） mechanism, which resulted in the larger fraction of DRX as well as finer and more uniform grain structure in the aged alloy specimens compared to the solution-treated alloy.

Characterization of hot deformation behavior of 30Si2MnCrMoVE low-alloying ultra-high-strength steel by constitutive equations and processing maps

Isothermal compression tests of as-forged 30Si2MnCrMoVE low-alloying ultra-high-strength steel were carried out on a Gleeble 3500 thermal simulator at the deformation temperatures of 950-1150℃and strain rates of 0.01-10 s^−1.Based on the classical stress-dislocation density relationship and the kinematics of the dynamic recrystallization,the constitutive equations of the work hardening dynamical recovery period and dynamical recrystallization period were developed by using the work hardening curve and Avrami equation,which shows good agreement with the experimental value.Processing maps at the strain of 0.90 were constructed based on dynamic material model and were analyzed combined with microstructure observation under different conditions.The optimum parameter based on the processing maps was obtained and verified by a supplementary experiment.The power dissipation maps and instability maps at strains of 0.05-0.90 were also constructed,and the evolution law was analyzed in detail.The established constitutive equation and hot processing maps can provide some guidance for hot working process.