Processing Map For Hot Working Research Articles

Influence of homogenization on the processing map for hot working of as-cast Mg–2Zn–1Mn alloy

Abstract Processing maps have been developed for hot deformation of Mg–2Zn– 1Mn alloy in as-cast condition and after homogenization with a view to evaluate the influence of homogenization. Hot compression data in the temperature range 300 – 500 °C and strain rate range 0.001 – 100 s– 1 were used for generating the processing map. In the map for the as-cast alloy the domain of dynamic recrystallization occurring at 450 °C and 0.1 s–1 has merged with another domain occurring at 500 °C and 0.001 s– 1 representing grain boundary cracking. The latter domain is eliminated by homogenization and the dynamic recrystallization domain expanded with a higher peak efficiency occurring at 500 °C and 0.05 s–1. The flow localization occurring at strain rates higher than 5 s–1 is unaffected by homogenization.

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−1 and 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.

Characterization of hot deformation behavior of as-forged TiAl alloy

The deformation behavior of as-forged Ti–43Al–9V–Y alloy was investigated by hot compression tests in the temperature range of 1100–1225 °C and strain rate range of 0.01–0.5 s−1. The results show that the alloy exhibits negative temperature sensitivity and positive strain rate sensitivity. The stress exponent (n = 3.02) and the apparent activation energy (Q = 342.27 kJ/mol) of the present alloy are lower than that of previous reported TiAl alloys, which suggests that the as-forged Ti–43Al–9V–Y alloy exhibits better deformability at low temperatures and high strain rates. A processing map for hot working was developed on the basis of a dynamic material model. The deformation mechanisms were analyzed by the processing map. The optimum processing condition at the strain of 0.6 is 1180–1210 °C/0.01–0.05 s−1. A crack-free Ti–43Al–9V–Y sheet was prepared by hot rolling at these optimized parameters. EBSD results show that dynamic recrystallization is more likely to occur for γ phase.

Hot deformation mechanisms, microstructure and texture evolution in extruded AZ31–nano-alumina composite

Processing map for hot working of hot extruded AZ31–1.5 vol% nano-alumina magnesium composite (AZ31–NAL) prepared by disintegrated metal deposition (DMD) technique has been developed in the temperature range of 250–500°C and strain rate range of 0.0003–10s−1. The starting composite microstructure is fine grained and is much less textured compared with the base AZ31 material prepared by similar technique (AZ31–DMD). The processing map for the composite exhibits three domains in the temperature and strain rate ranges: (1) 250–350°C/0.0003–0.01s−1; (2) 375–500°C/0.0003–0.01s−1; (3) 300–400°C/1–10s−1, which are all similar to those exhibited by the base alloy. In Domains #1 and #3, dynamic recrystallization occurs and results in fine grained microstructure, while in Domain #2, grain boundary sliding leading to wedge cracking in compression and intercrystalline cracking in tension have been identified. In comparison with the base alloy AZ31–DMD, the efficiency in the first domain has decreased, the third domain moved to lower temperatures and the effect on second domain is marginal. These differences are attributed to the lower intensity of starting texture in the nano-composite compared with the base alloy. A study of texture changes in the deformed specimens revealed that nano-alumina additions are helpful in reducing the preferred orientation in AZ31 alloy.

Constitutive analysis and processing map for hot working of a Ni-Cu alloy

The hot deformation behavior of a Ni-Cu alloy was studied using hot compression testing in the temperature range of 950 °C–1150 °C and at strain rates of 0.001 s−1-1 s−1. Flow curves at low strain rates, up to 0.01 s−1, were typical of DRX characterized by a single peak, while at higher strain rates, the typical form of a DRX flow curve was not observed. The power-law constitutive equation was used to correlate flow stress to strain rate and temperature, and the apparent activation energy of hot deformation was determined to be about 462.4 kJ/mol. The peak strain and stress were related to the Zener-Hollomon parameter and the modeling formula was proposed. The dependence of flow stress to the Z changed at ln Z=38.5, which was considered to be a critical condition for the change in the mechanism of dynamic recrystallization. The efficiency of power dissipation was determined to be between 10–35 percent at different deformation conditions. According to the dynamic material model, stable flow was predicted for the studied temperature and strain rate ranges. Highly serrated grain boundaries at low strain rates were considered to be a reason for the occurrence of continuous dynamic recrystallization. On the contrary, at high strain rates, equiaxed grain structure was attributed to the typical discontinuous dynamic recrystallization.

Hot working mechanisms and texture development in Mg-3Sn-2Ca-0.4Al alloy

Hot deformation mechanisms in Mg-3Sn-2Ca (TX32) alloy containing 0.4% Al are evaluated in the temperature and strain rate ranges of 300–500 °C and 0.0003–10 s−1 using processing map and kinetic analysis. The evolution of microstructure and texture during high temperature compression of the alloy has been studied using an electron back scatter diffraction (EBSD) technique. The processing map for hot working revealed two domains of dynamic recrystallization (DRX) occurring in the temperature and strain rate ranges of: (1) 300–360 °C and 0.0003–0.001 s−1 and (2) 400–500 °C and 0.005–0.7 s−1, which are the two safe hot workability windows for this alloy. A regime of flow instability occurs at higher strain rates and lower temperatures where adiabatic shear banding and flow localization are the microstructural manifestations. The onset of DRX during compression at lower temperatures and strain rates (Domain 1) resulted in a fine, partially recrystallized and necklaced grain microstructure along with a texture where the basal poles are spread along 30° from the compression direction. Specimens deformed at temperatures higher than 450 °C (Domain 2) resulted in a fully recrystallized microstructure and an almost random crystallographic texture, which was attributed to the significant occurrence of pyramidal slip and associated cross-slip.

Hot Deformation Behavior of Nickel-Based Superalloy GH4720Li

The hot deformation characteristics of GH4720Li alloy were studied at the temperature of 1100 – 1170 °C and strain rate of 0. 01–1 s−1 using Gleeble hot compression tests. True stress-true strain curves and deformation microstructures were investigated. Constitutive equation was established using the hyperbolic law. Processing map for hot working was also developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate. The results show that dynamic recrystallization is the dominant softening mechanism during hot deformation. Fully recrystallized grain is obtained at strain of 0. 7 above 1130 °C, and coarsening occurs above 1150 °C. The mean deformation activation energy is determined to be 512 kj/mol. According to the low activation energy value, high dissipation efficiency parameter and fine recrystallized microstructure, 1130 °C is chosen as the hot working temperature for GH4720Li alloy.

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 0.01–10mms−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 0.001–0.01s−1, (2) 650–950°C and 0.3–30s−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.

Processing map for hot working of Inconel 718 alloy

Cylindrical specimens of Inconel 718 alloy with grain size of 90 μm were used in the compression tests and processing maps at the strains of 0.1, 0.3, 0.5 and 0.7 were developed at 950–1150 °C in the strain rate range 0.001–100 s −1. Only one unstable region for adiabatic shear bands and one small dynamic recrystallization zone in the stable region are exhibited in the processing map at 0.1 strain. As the strain is beyond 0.3, there exist three unstable regions in the processing maps where one is for adiabatic shear bands and the other two are for intergranular cracking. At the same time, the zone of dynamic recrystallization with a peak efficiency of 0.39 at about 950 °C and 0.001 s −1 in the stable region is enlarged and the distribution of which is from lower temperature and lower strain rate to higher ones. Optical micrographs of the specimens compressed to 0.7 strain show good agreement with the processing maps and main hot working schedules have been designed. Influence of initial grain size from 10 μm to 90 μm on the occurrence temperature of adiabatic shear bands and intergranular cracking has been analyzed at a strain rate of 100 s −1 and in the temperature range 900–1200 °C.

Processing map for hot working of SiC p/7075 Al composites

Abstract 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 °C 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 −1 and temperature range of 390–440 °C with the efficiency of 30%.

Processing map for hot working of spray formed and hot isostatically pressed Al–Li alloy (UL40)

The hot deformation behavior of spray formed + HIPed Al–Li (UL40) alloy was studied using processing map technique. The map has been interpreted in terms of the microstructural processes occurring in situ with deformation, based on the values of a dimensionless parameter η which is an efficiency index of energy dissipation through microstructural processes. An instability criterion has also been applied to demarcate the flow instability regions in the processing map using another parameter ( ξ). Both the parameters ( η and ξ) were computed from the experimental data generated by compression tests conducted at various temperature and strain rate combinations over the hot working range (375–575 °C and 3 × 10 −4 to 1 s −1) of the present material. The processing map exhibits three distinct η domains without any unstable flow conditions under the investigated temperature and strain rate conditions. The dominant microstructural mechanisms corresponding to these domains were identified to be extended dynamic recovery, grain boundary cavitation and flow localization. The stress–strain, microstructure and hot ductility recorded under the deformation conditions of these domains were correlated to the microstructural processes. The ‘safe window’ for hot working of HIPed UL40 material has been identified based on these results. Further, the significance of HIPing on the hot workability has been enunciated by comparing the results of the present material with the as-spray formed material.

Spray Casting of Al-25Si Alloy and Hot Deformation Behavior

The spray forming process was used to produce Al-25Si alloy in this study. The microstructure of the hypereutectic Al-25Si alloy appeared to consist of Al matrix and equiaxed Si particles with average diameter of 5~7 µm. To deduce the extrusion condition, a series of compression tests has been conducted at temperatures ranging from RT to 500oC. The strain rate sensitivity parameter (m) of this alloy has been found to be very low ( ≤0.1) below 300oC and reached maximum value of about 0.13 at 500°C. The extrusion has been successfully conducted at the temperatures of 300°C and above with the ratio of area reduction of 28 and 40. The processing map for hot working has also been constructed.

Influence of homogenization on the processing map for hot working of as-cast Mg–2Zn–1Mn alloy

Processing maps have been developed for hot deformation of Mg-2Zn-1Mn alloy in as-cast condition and after homogenization with a view to evaluate the influence of homogenization. Hot compression data in the temperature range 300-500degreesC and strain rate range 0.001-100 s(-1) were used for generating the processing map. In the map for the as-cast alloy the domain of dynamic recrystallization occurring, at 450degreesC and 0.1 s(-1) has merged with another domain occurring at 500degreesC and 0.001 s(-1) representing grain boundary cracking. The latter domain is eliminated by homogenization and the dynamic recrystallization domain expanded with a higher peak efficiency occurring at 500 degreesC and 0.05 s(-1). The flow localization occurring at strain rates higher than 5 s(-1) is unaffected by homogenization.

Application of neural networks in generating processing map for hot working

An important parameter in the mechanical working of materials is called workability, which is the relative ease with which a metal can be shaped through plastic deformation without the formation of any defect. Workability can be evaluated by means of processing maps, constructed from experimentally generated flow stress variation with respect to strain, strain rate and temperature. The present work demonstrates the use of neural network in generating processing maps for hot working processes. A neural network model was trained and tested for predicting the flow stress by taking data available in the literature for 99.99% pure aluminum. It was found that the trained neural network could predict the flow stress for unseen data quite reliably. At strain of 0.4, power dissipation and instability maps were constructed, utilizing the flow stress prediction by neural network. Superimposition of these maps provided processing maps at 0.4 strain, which was similar to that available in the literature. This established the potential of applying neural network, which is more robust technique than conventional method, for generating the processing map.

Processing map for hot working of hot-rolled Mg-11.5Li-1.5Al-0.15Zr alloy

Processing map for hot working of hot-rolled Mg-11.5Li-1.5Al-0.15Zr alloy

Microstructural mechanisms during hot working of commercial grade Ti–6Al–4V with lamellar starting structure

The hot deformation behavior of commercial grade Ti–6Al–4V with a lamellar starting microstructure is studied in the temperature range 750–1100°C and strain rate range 3×10−4–10 s−1 with a view to model the microstructural evolution. On the basis of flow stress data obtained as a function of temperature and strain rate in compression, a processing map for hot working has been developed. In the ranges 800–975°C and 3×10−4–10−2 s−1, globularization of lamellae occurs for which an apparent activation energy of 455 kJ mol−1 has been estimated using the kinetic rate equation. Stress-dependent thermal activation analyses proposed by Schöck and Cocks et al. have shown that the apparent activation energies are in the range 160–245 kJ mol−1 and the normalized activation volumes are in the range 20–80, which suggest that cross-slip is the rate controlling process during globularization. The variation of primary α grain size with Zener–Hollomon parameter (Z) in the globularization region exhibited a linear relationship on a log–log scale. At strain rates slower than 10−1 s−1 and temperatures below 900°C, cracking at the prior β grain boundaries/triple junctions occurs, which sets the lower limits for globularization. At strain rates higher than 10−1 s−1 in the α+β range, the material exhibited flow instabilities manifested as adiabatic shear bands. These bands are intense below 800°C and above 1 s−1 and caused cracking along the bands. In the β phase field, dynamic recrystallization (DRX) occurs at about 1100°C and in the strain rate range 10−3–10−1 s−1. The apparent activation energy for DRX of β is about 172 kJ mol−1 which is close to that for self-diffusion in β phase (153 kJ mol−1). The application of these results in the design of bulk metalworking processes for achieving microstructural control is discussed.

Characteristics of superplasticity domain in the processing map for hot working of as-cast Mg–11.5Li–1.5Al alloy

Processing map for hot working of as-cast Mg–11.5Li–1.5Al alloy has been developed in the temperature range 200–450°C and strain rate range 0.001–100 s −1. The map exhibited a single domain with a peak efficiency of 65% occurring at 400°C and 0.001 s −1. Under these conditions, the material exhibited abnormal elongation. On the basis of the elongation, the grain structure, the apparent activation energy for hot deformation (95 kJ mole −1) and the peak efficiency of power dissipation (65% corresponding to a strain rate sensitivity of about 0.5), the domain is interpreted to represent superplasticity. At strain rates higher than about 10 s −1, the material exhibits microstructural instability, while at temperatures of 450°C and a strain rate of 0.001 s −1, grain boundary cracking is observed.

Comment on “Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 2014-20vol.% Al 2O 3 metal matrix composite”

New processing maps for hot working of an aluminium alloy were constructed. The apparent activation energy, Q, and the temperature sensitivity parameter, s, were computed, mapped over a given range of processing conditions and used to select the optimum processing conditions. An alternative interpretation of the data was suggested.

Processing map for hot working of 6061 Al–10 vol.-%Al2O3metal matrix composite

The processing map for hot working of 6061 Al–10 vol.-%Al2 O3(p) particulate reinforced cast and extruded composite material has been generated covering the temperature range 350–550°C and the strain rate range 0·001–100 s−l, based on the dynamic materials model. The efficiency of power dissipation η, given by (2m/m + 1), where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of dynamic recrystallisation has been identified, with a peak efficiency of 32% occurring at 550°C and 0·1 s−l. Another domain occurs at 350°C and 0·001 s−l, having a similar efficiency level, which is identified with interface cracking. The characteristics of these domains have been established with the help of microstructural evaluation and hot ductility measurements. Optimum hot working parameters are 550°C and 0·1 s−l, whereas microstructural instability occurs at strain rates higher than 10 s−l at all temperatures.MST/2033

Characteristics of superplasticity domain in the processing map for hot working of an Al alloy 201420vol.%Al 2O 3 metal matrix composite

The processing map for hot working of Al alloy 201420vol.%Al 2O 3 particulate-reinforced cast-plus-extruded composite material has been generated covering the temperature range 300–500 °C and the strain rate range 0.001–10 s −1 based on the dynamic materials model. The efficiency η of power dissipation given by 2m (m + 1) , where m is the strain rate sensitivity, is plotted as a function of temperature and strain rate to obtain a processing map. A domain of superplasticity has been identified, with a peak efficiency of 62% occurring at 500 °C and 0.001 s −1. The characteristics of this domain have been studied with the help of microstructural evaluation and hot-ductility measurements. Microstructural instability is predicted at higher strain rates above (1s −1) and lower temperatures (less than 350 °C).