Processing maps for hot-working of powder metallurgy 1100 Al-10 vol % SiC-particulate metal-matrix composite

The hot-working characteristics of the metal-matrix composite (MMC) Al-10 vol % SiC-particulate (SiC_p) powder metallurgy compacts in as-sintered and in hot-extruded conditions were studied using hot compression testing. On the basis of the stress-strain data as a function of temperature and strain rate, processing maps depicting the variation in the efficiency of power dissipation, given by = 2m/(m+1), where m is the strain rate sensitivity of flow stress, have been established and are interpreted on the basis of the dynamic materials model. The as-sintered MMC exhibited a domain of dynamic recrystallization (DRX) with a peak efficiency of about 30% at a temperature of about 500°C and a strain rate of 0.01 s^–1. At temperatures below 350°C and in the strain rate range 0.001–0.01 s^–1 the MMC exhibited dynamic recovery. The as-sintered MMC was extruded at 500°C using a ram speed of 3 mm s^–1 and an extrusion ratio of 101. A processing map was established on the extruded product, and this map showed that the DRX domain had shifted to lower temperature (450°C) and higher strain rate (1 s^–1). The optimum temperature and strain rate combination for powder metallurgy billet conditioning are 500°C and 0.01 s^–1, and the secondary metal-working on the extruded product may be done at a higher strain rate of 1 s^–1 and a lower temperature of 425°C.     

Processing maps for hot working of Cu-Ni-Zn alloys

The constitutive behaviour of — nickel silver in the temperature range 700–950 °C and strain rate range 0.001–100 s^–1 was characterized with the help of a processing map generated on the basis of the principles of the dynamic materials model of Prasadet al Using the flow stress data, processing maps showing the variation of the efficiency of power dissipation (given by 2m/(m+1) wherem is the strain-rate sensitivity) with temperature and strain rate were obtained, -nickel silver exhibits a single domain at temperatures greater than 750 °C and at strain rates lower than 1s^–1, with a maximum efficiency of 38% occurring at about 950 °C and at a strain rate of 0.1 s^–1. In the domain the material undergoes dynamic recrystallization (DRX). On the basis of a model, it is shown that the DRX is controlled by the rate of interface formation (nucleation) which depends on the diffusion-controlled process of thermal recovery by climb. At high strain rates (10 and 100s^–1) the material undergoes microstructural instabilities, the manifestations of which are in the form of adiabatic shear bands and strain markings.     

Hot deformation behavior of an extruded Mg-Li-Zn-RE alloy

A new Mg-7.8%Li-4.6%Zn-0.96%Ce-0.85%Y-0.30%Zr alloy has been developed. α phase, β phase and RE-containing intermetallics formed in the alloy. It is found that the alloy can easily be extruded at 260 °C with σ_0.2 = 256 MPa, σ_b = 260 MPa and δ = 14%. Hot deformation behavior of the extruded alloy was studied using the processing map technique. Compression tests were conducted in the temperature range of 250-450 °C and strain rate range of 0.001-10 s⁻¹ and the flow stress data obtained from the tests were used to develop the processing map. The different efficiency domains and flow instability region corresponding to various microstructural characteristics have been identified as follows: (1) Domain I occurs in the temperature range of 250-275 °C and strain rate range of 1-10 s⁻¹, with a peak efficiency of about 50% at 250 °C/10 s⁻¹. Incomplete DRX process has occurred in β phase and DRX process hardly occurs in α phase; (2) Domain II occurs in the temperature range of 250-275 ?C and strain rate range of 0.001-0.003 s⁻¹, with a peak efficiency of about 42% at 250 °C/0.001 s ⁻¹. Incomplete DRX process has occurred in β phase and α phase; (3) Domain III occurs in the temperature range of 400-450 °C and strain rate range of 1-10 s⁻¹, with a peak efficiency of about 42% at 450 °C/10 s⁻¹. Complete DRX process has occurred in β phase and α phase. No cracking, cavity and band of flow localization are observed in flow instability region. The optimum parameters for hot working of the alloy are 250 °C/10 s⁻¹ and 250 °C/0.001 s⁻¹, at which fine dynamic recrystallization microstructure will be achieved. RE-containing intermetallics and α phase accelerate the DRX process in β phase. The softer β phase reduces the driving force for DRX process in α phase, so DRX process in α phase is retarded.     

Hot Deformation Characteristics for a Nickel-base Superalloy GH742y

The hot deformation characteristics of as-cast nickel-base superalloy GH742y after hot isostatic pressing (HIP)(hereafter referred to as-cast alloy) have been investigated by hot compression tests in the temperature range of 1050 to 1140℃, strain rate range of 0.01 s-1 to 10 s-1 and strain range of 35% to 50% by means of Gleeble-3500 thermal mechanical simulator.The results show that the as-cast alloy exhibits the poor deformability, and shows wedge-shaped cracking beyond the strain of 35%.At strain rates less than 1.0 s-1,the stress-strain curves exhibit nearly steady-state behavior, while at strain rate of 10 s-1, a yield drop and serrated yielding occur.The activation energy values developed on the basis of the experimental data are divided into three domains.The first domain appears at lower strain rate (≤1.0 s-1) and lower temperature (≤1080℃), with the lowest mean value of activation energy about 261.4 kJ/mol.The second domain appears at the same strain rate as the first domain, but higher temperature (>1080℃), with the intermediate mean value of activation energy about 328.8 kJ/mol.The third domain appears at higher strain rate (10 s-1) and temperature range of 1050 to 1140℃, with the largest mean value of activation energy about 605.05 kJ/mol.Three different constitutive equations are established in corresponding to domains.Microstructural observations in the third domain reveal non-uniform dynamic recrystallization (DRX) of homogeneous γ phase, which leads to the poor deformability and the highest Q value.In contrast, microstructures in the first domain show fully DRX of homogeneous γ phase, leading to the better deformability and the lowest Q value.It is noted that the grain size increases with the increment of strain rate or temperature.These results suggest that bulk metal working of this material may be carried out in the first domain where fully DRX of γ homogeneous occurred.     

Characterization of dynamic recrystallisation in as-homogenized Mg–Zn–Y–Zr alloy using processing map

The hot working behavior of a as-homogenized Mg–Zn–Y–Zr alloy has been investigated in the temperature range 200–400°C and strain rate range 0.0015–7.5 s⁻¹ using processing map. The power dissipation map reveals that a domain of dynamic recrystallisation (DRX) in the temperature range 300–400°C and strain rate range 0.0015–0.15 s⁻¹, with its peak efficiency of 38% at 350°C and 0.0015 s⁻¹, which are the optimum hot working parameters. The apparent activation energy in the hot deformation process is 148 ± 3 KJ/mol that is larger than that of ZK60 alloy because of the obstruction of Y atoms for diffusion. DRX model indicates that DRX of Mg–Zn–Y–Zr alloy is controlled by the rate of nucleation, which is lower one order of magnitude than growth. And the rate of nucleation depends on the process of mechanical recovery by cross-slip of screw dislocations.     

Materials modeling and finite element simulation of isothermal forging of electrolytic copper

Isothermal forging of electrolytic copper is modeled using finite element simulation and materials models involving kinetic analysis and processing maps with a view to validate their predictions. Forging experiments were conducted on a rib–web (cup) shape in the temperature range of 300–800 °C and at speeds of 0.01–10 mm s⁻¹. The processing map for hot working of electrolytic copper revealed two domains in the temperature and strain ranges of (1) 400–600 °C and 0.001–0.01 s⁻¹, (2) 650–950 °C and 0.3–30 s⁻¹, where dislocation core diffusion and lattice self-diffusion are the rate-controlling mechanisms, respectively. Finite element simulation using the relevant experimental constitutive equations, predicted load–stroke curves that correlated well with the experimental data. The simulation has shown that there is a strain variation from about 0.4 to 4 in the web and rib regions of the forged component, although the dynamically recrystallized grain structure is fairly uniform, suggesting that dynamic recrystallization (DRX) is not sensitive to strain once the steady state flow is reached. The DRX grain size in the component is linearly dependent on Z and is similar to that predicted by the materials model after discounting for the longer time taken for the component removal.     

A study on hot deformation behavior of Ni-42.5Ti-7.5Cu alloy

To investigate the hot deformation behavior of the Ni-42.5Ti-7.5Cu (wt%) alloy, hot compression tests were carried out at the temperatures from 800 °C to 1000 °C and at the strain rates of 0.001 s⁻¹ to 1 s⁻¹. The results show that the occurrence of dynamic recrystallization (DRX) is the dominate restoration mechanism during the hot deformation of this alloy. There is an increase in peak and steady state stresses with decreasing the deformation temperature and increasing the strain rate. The experimental results were then used to determine the constants of developed constitutive equations. There is a good agreement between the measured and predicted results indicating a high accuracy of developed model. Zener–Hollomon (Z) parameter, calculated based on the developed model, indicates that DRX was postponed when the logarithm of the Zener–Hollomon parameter fell around 33 at strain rate of 0.001 s⁻¹ and temperature of 900 °C. This phenomenon can be regarded as the interactions between solute atoms and mobile dislocations. The established constitutive equations can be used to predict and analyze the hot deformation behavior of Ni-42.5Ti-7.5Cu alloy.     

Effects of strain on the workability of a high strength low alloy steel in hot compression

Based on the experimental results from the hot compression tests of 42CrMo steel, the efficiencies of power dissipation and instability parameter were evaluated. The effects of strain on the efficiency of power dissipation and instability parameter of 42CrMo steel have been discussed in detail. Processing maps were constructed by superimposition of the instability map over the power dissipation map. The dynamic recrystallization domains and instable zones were identified in the processing map. The effects of strain on microstructural evolutions were correlated with the processing maps. According to the 3D processing maps, the optimum domain of hot deformation is in the temperature range of 1050–1150 °C and strain rate range of 0.01–3 s⁻¹, with its peak efficiency of 32% at about 1140 °C and 0.23 s⁻¹, which are the optimum hot working parameters.     

Research on the hot deformation behavior of Ti40 alloy using processing map

The deformation behavior of a Ti40 titanium alloy was investigated with compression tests at different temperatures and strain rates to evaluate the activation energy and to establish the constitutive equation, which reveals the dependence of the flow stress on strain, strain rate and deformation temperature. The tests were carried out in the temperature range between 900 and 1100 °C and at strain rates between 0.01 and 10 s⁻¹. Hot deformation activation energy of the Ti40 alloy was calculated to be about 372.96 kJ/mol. In order to demonstrate the workability of Ti40 alloy further, the processing maps at strain of 0.5 and 0.6 were generated respectively based on the dynamic materials model. It is found that the dynamic recrystallization of Ti40 alloy occurs at the temperatures of 1050-1100 °C and strain rates of 0.01-0.1 s⁻¹, with peak efficiency of power dissipation of 64% occurring at about 1050 °C and 0.01 s⁻¹, indicating that this domain is optimum processing window for hot working. Flow instability domains were noticed at higher stain rate (≥1 s⁻¹) and stain (≥0.6), which located at the upper part of the processing maps. The evidence of deformation in these domains has been identified by the microstructure observations of Ti40 titanium alloy.     

Evaluation of hot workability of particle reinforced aluminum matrix composites by using deformation efficiency

The high temperature deformation behavior of Al 6061 composites reinforced with SiC and Al₂O₃ particles has been studied in the temperature range of 300–550°C and the strain rate range of 0.1–3.0/sec by hot torsion test. The deformation efficiency , given by (2m/m + 1), where m is the strain rate sensitivity, is calculated as a function of temperature and strain rate to obtain iso-efficiency contour map. The composite reinforced with SiC particle exhibited a domain of dynamic recrystallization (DRX) with a peak efficiency of 40% at the temperature range of 450–500°C and strain rate range of 0.2–0.5/sec. On the other hand, the composite reinforced with Al₂O₃ particle showed the DRX domain at the temperature range of 450–480°C and strain rate range of 0.1–0.2/sec. The characteristics of these domain have been investigated with the help of microstructural observation and hot ductility measurements.     

The Hot Workability of SiCp/2024 Al Composite by Stir Casting

The hot workability of SiC_p/2024 Al composite was explored by conducting hot compression simulation experiments on Gleeble-3500 under temperatures of 300–500 °C and strain rates of 10^?3–1 s^?1. Constitutive equation was developed through hyperbolic sine function, and the activation energy was calculated to be 151 kJ mol^?1. The hot processing maps referring to dynamic material model were drawn in a true strain range from ?0.2 to ?0.8. At the strain of ?0.8, the recommended regions in processing map contained two domains: superplastic domain (500 °C, 10^?3 s^?1) with an efficiency of about 0.72 and DRX domain (500°C, 1 s^?1) with an efficiency of about 0.45. Together with macrostructure and microstructure observations, it was suggested to remove the DRX region.     

Hot deformation and processing maps of extruded ZE41A magnesium alloy

The hot deformation behavior and microstructure evolution of extruded ZE41A magnesium alloy has been studied using the processing map. The compression tests were conducted in the temperature range of 250–450 °C and the strain rate range of 0.001–1.0 s⁻¹ to establish the processing map. The dynamic recrystallization (DRX) and instability zones were identified and validated through micrographs. The observations were performed in order to describe the behavior of the material under hot forming operation in terms of material damage and micro-structural modification.     

Prediction of dynamic recrystallization condition by deformation efficiency for Al 2024 composite reinforced with SiC particle

Hot torsion test has been carried out for Al 2024 composite reinforced with 8 m SiCp (15 vol.%) to suggest optimum hot working condition for dynamic recrystallization (DRX) at the temperature range of 320 to 520 °C and strain rate range of 0.1 to 3.0/sec. Flow curve and deformed microstructure have been analyzed to identify the hot restoration mechanism of DRX. Processing map showing the variation of the deformation efficiency expressed by [2m/(m + 1)], where m is the strain rate sensitivity, with temperature and strain rate has been described for the composite. The characteristics of domain of DRX and peak efficiency of the composite have been analyzed by observing deformed microstructure. The composite showed 40–50% efficiency at the DRX domain (370–460 °C, 0.1–0.5/sec). Also, the variation of deformation efficiency with Zener-Hollomon parameter (Z = exp(Q/RT)) were discussed to find out optimum hot working condition for DRX of the composite. It is found that the optimum temperature and strain rate condition for DRX of the composite is 430–450 °C and 0.5/sec.     

Effect of aluminum on microstructural evolution during hot deformation of TX32 magnesium alloy

The effect of Al (0.4 and 1 wt%) addition on the hot deformation behavior of the Mg–3Sn–2Ca (TX32) alloy has been studied with the help of processing maps generated in the temperature and strain rate ranges of 300–500 °C and 0.0003–10 s^?1. The deformed specimens have been examined as regards changes in texture and microstructure using electron back scatter diffraction and transmission electron microscopy, respectively. The map for the TX32 base alloy exhibited two dynamic recrystallization (DRX) domains in the temperature and strain rate ranges: (1) 300–350 °C and 0.0003–0.001 s^?1, and (2) 390–500 °C and 0.005–0.6 s^?1. While 0.4 wt% Al addition to TX32 did not result in any significant change in the processing map, the map for the alloy with 1 wt% Al (TX32-1Al) exhibited four domains in the ranges: (1) 300–325 °C and 0.0003–0.001 s^?1, (2) 325–430 °C and 0.001–0.04 s^?1, (3) 430–500 °C and 0.01–0.5 s^?1, and (4) 430–500 °C and 0.0003–0.002 s^?1. In the first three domains, DRX has occurred, whereas in the fourth domain, grain boundary sliding takes place causing intercrystalline cracking in tension. In Domain 1 for all the alloys, DRX has occurred predominantly by basal slip and recovery by climb as confirmed by the resulting basal texture and tilt type sub-boundary structure. In Domain 2 of the base alloy and Domain 3 of the alloy with 1 wt% Al, second-order pyramidal slip dominates associated with cross-slip which randomizes the texture, and forms tangled dislocations and twist type sub-boundaries in the microstructure. The addition of 1 wt% Al causes solid solution strengthening and results in Domain 2 of the map of TX32-1Al alloy and in this domain basal+prismatic slip dominate.     

Processing map for hot working of Ni–16Cr–8Fe alloy (IN 600)

Abstract

The hot deformation characteristics of IN 600 nickel alloy are studied using hot compression testing in the temperature range 850–1200°C and strain rate range 0·001–100 s^?l. A processing map for hot working is developed on the basis of the data obtained, using the principles of dynamic materials modelling. The map exhibits a single domain with a peak efficiency of power dissipation of 48% occurring at 1200°C and 0·2 s^?1, at which the material undergoes dynamic recrystallisation (DRX). These are the optimum conditions for hot working of IN 600. At strain rates higher than 1 s^?1, the material exhibits flow localisation and its microstructure consists of localised bands of fine recrystallised grains. The presence of iron in the Ni–Cr alloy narrows the DRX domain owing to a higher temperature required for carbide dissolution, which is essential for the occurrence of DRX. The efficiency of DRX in Ni–Cr is, however, enhanced by iron addition.

MST/1856     

Superplastic properties of a TiAl based alloy with a duplex microstructure

The superplastic properties of a engineering TiAl based alloy with a duplex microstructure were investigated with respect to the effect of testing temperatures ranging from 950°C to 1075°C and strain rates ranging from 8 × 10^–5 s^–1 to 2 × 10^–3 s^–1. A maximum elongation of 467% was achieved at 1050°C and at a strain rate of 8 × 10^–5 s^–1. The apparent activation energy was calculated to be 345 kJ/mol. Also, the dependence of the strain rate sensitivity values on strain during superplastic deformation was examined through the jump strain rate tests, and microstructural analysis was performed after superplastic deformation. It is concluded that superplasticity of the alloy at relatively low temperature and relatively high strain rate results from dynamic recrystallization, and grain boundary sliding and associated accommodation mechanism is related to superplasticity at higher temperature and lower strain rate.     

Processing map for hot working characteristics of a wrought 2205 duplex stainless steel

Processing map on a wrought 2205 duplex stainless steel under hot compression conditions has been developed based on the dynamic material model theories in the range 1223–1473 K and 0.01–10 s⁻¹. The various domains in the map corresponding to different deformation characteristics have been discussed in combination of microstructural observations. The results show that the power dissipation efficiency (η) depends strongly on the dynamic recrystallization (DRX) of austenite which plays a dominant role in microstructural evolution, while the ferrite phase mainly continues to exhibit relatively well-developed dynamic recovery (DRV) at large strain. The optimum hot working domain of wrought 2205 duplex stainless steel is obtained to be in the temperature range 1373–1473 K and at strain rate of 0.01 s⁻¹, with peak efficiency 50% occurring at about 1423 K, in which more uniform microstructure is developed due to the occurrence of complete DRX of austenite. The unstable hot working regimes are predicted by Prasad instability criterion, in good agreement with the macro-and microstructural observations. As predicted, flow instability, which are manifested as twinning, bands of flow localization and the absence of DRX in austenite are observed at lower temperatures and higher strain rates (1223–1273 K and 1–10 s⁻¹); in other cases, wedge cracking is responsible for instability phenomena observed at the temperature range 1373–1423 K and strain rate of 10 s⁻¹.     

Hot deformation behavior and microstructural evolution of Ag-containing 2519 aluminum alloy

The hot deformation behaviors of Ag-containing 2519 aluminum alloy were studied by isothermal compression at 300–500 °C with strain rates from 0.01 s⁻¹ to 10 s⁻¹. The microstructural evolution of the alloy was investigated using Polyvar-MET optical microscope and Tecnai G² 20 transmission electron microscope (TEM). It has been shown that the flow stress of the alloy increases with increasing the strain rate and decreasing the deformation temperature. When the strain rate is lower than 10 s⁻¹, the flow stress increases with increasing strain until the stress reached the peak value, after which the flow stress remains almost constant. This result indicates that dynamic recovery happens during deformation. When the strain rate is 10 s⁻¹ and the temperature is higher than 300 °C, serrated flow behavior is generally observed with the stress decreasing with increasing strain, a typical phenomenon of dynamic recrystallization.     

The rate dependent response of a titanium alloy subjected to quasi-static loading in ambient environment

A dual phase Ti-6A1-4V alloy was tested in uniaxial tension over a large quasi-static loading range (10^–5–10^–1 s^–1) in ambient environment. As strain rate increases, strength of the alloy was found to increase at the expense of ductility. In the low strain-rate region, strain rate sensitivity of the material experienced a gradual decrease during plastic deformation. In the high strain-rate region, strain-rate sensitivity of the material was largely constant for most part of the plastic deformation. The different rate dependent behaviours are believed to be caused by a change of governing plastic deformation mechanism from dislocation slip at low strain rates to twinning at the highest strain rate. Strong fractographic and metallographic evidence was obtained to understand the micromechanisms of plastic deformation.     

Experimental analysis and constitutive modeling for the newly developed 2139-T8 alloy

Mechanical behavior of recently emerged 2139-T8 aluminum alloy, which is based on an Al–Cu–Mg–Ag system, has been characterized by uniaxial compression and tension experiments over a wide range of strain rates from 10⁻⁴ to 10⁴ s⁻¹ and for temperatures from −60 to 300 °C. Driven by experimental results, modifications to widely used Johnson–Cook constitutive model has been proposed, and model parameters have been determined. It has been shown that modified Johnson–Cook (MJC) model satisfactorily captures rate- and temperature-dependent variations in flow stress through enhanced coupling between temperature and strain hardening as well as temperature and strain-rate sensitivity. The modified model also provides flow stress prediction over the entire range of quasi-static and dynamic regimes by a single continuous function.