Multiaxial Forging Research Articles

AA2219 Aluminum Alloy Processed via Multi-Axial Forging in Cryogenic and Ambient Environments

This paper presents the microstructure and the mechanical behavior of nanocrystalline AA2219 processed by multi axial forging (MAF) at ambient and cryogenic temperatures. The X-ray diffraction pattern and transmission electron microscopy micrographs in the initial microstructure characterization indicate a more effective severe plastic deformation during the cryogenic MAF than the same process conducted at room temperature. MAF at cryogenic temperature results in crystallite size reduction to nanoscales as well as second phase particles breakage to finer particles which are the crucial factors to increasing the mechanical properties of the material. Fractography analysis and tensile tests results show that cryogenic forging does not only increase the mechanical strength and toughness of the alloys significantly, but also improves the ductility of the material in comparison with the conventional forging. In this comparative regard, cryogenic processing provides 44% increase in the tensile strength of the material only after 2 forging cycles when compared to the room temperature process. In addition, further forging process to the next cycles slightly enhances the tensile strength at the expense of ductility due to less ability of the dislocations to accumulate. However, the ductility of the ambient temperature forged samples decreases at a faster rate than that of cryoforged samples.

Effects of combined multiaxial forging and rolling process on microstructure, mechanical properties and corrosion behavior of a Cu–Ti alloys

Combined multiaxial forging (MAF) and rolling was performed on Cu-3% Ti (wt%) alloy at room temperature with emphasis on microstructural evolution, improvement in mechanical properties, and corrosion resistance. Microstructural changes were confirmed from various characterization techniques, and co-related with mechanical properties. TEM analysis revealed high shear band density in the 3 pass MAF + 90% rolled sample appearing due to high strain. EBSD analysis revealed transformation to low angle grain boundaries from high angle grain boundaries. Maximum microhardness and UTS reached to 340 HV and 960 MPa, respectively in the processed samples. Significant grain refinement was observed in MAF processed Cu-3%Ti alloy, and after combined MAF + rolling, higher dislocation density and refinement of shear bands were observed. In addition, potentio-dynamic polarization test was used to study the corrosion behavior of the alloy. Scanning electron microscope (SEM) was used to analyze the corroded surface morphology.

Pre-heating of multi-axial forging (MAF) on aluminum based composites

Aluminum is one of the materials used for automotive, almost 90% of aluminum scrap from automotive cars can be recycled. The properties of aluminum are light and have a high ductility. The addition of SiC as reinforcement to aluminum based composite materials by multi-axial forging (MAF) is one of the newly developed SPD processes. Addition of SiC is to increase strength greater than the base material. The purpose of this research is to know the micro structure especially spread of distribution of precipitate evenly in matrix and change of mechanical properties after MAF process. Therefore, variation of weight fraction of SiC and pre-heating temperature were conducted. Kind of aluminum type AA1100 shaped plate as matrix added SiC as reinforcement, using variation 0.2%:0.4% and 0.6% wt. As for pre-heating temperature variation of 350°C, 450°C and 550°C then done MAF process with every change of pass rotate 90°. The results obtained from aluminum-based composite study by MAF, that with the addition of SiC on microstructure observation there is a change of grain boundary shape from equaxial to lamellar, there are grains of precipitate on the matrix that spread evenly and tensile test results and microhardness test increased along with the addition SiC fraction at a temperature of 350°C while for temperatures of 450°C and 550°C there is a decrease in hardness value, tensile strength value on Al/SiC.

Strain Behavior of Nickel Alloy 200 during Multiaxial Forging through Finite Element Modeling

Multiaxial forging (MAF) is one of the appealing methods of severe plastic deformation (SPD) techniques to fabricate ultrafine-grained (UFG) materials. In this study; the influence of process parameters such as strain rate; friction; and initial temperature has been assessed through finite element simulation of Nickel 200 alloy. The Johnson–Cook equation was applied in simulating the MAF process. The homogeneous microstructure of a material processed by MAF is an important requirement to obtain uniform mechanical and other properties. The uniformity in properties was evaluated by the investigation of the hardness measurements; effective strain (ES), and inhomogeneous factor (IF) or coefficient of standard deviation. The results showed that the inhomogeneous factor decreases with an increase in strain rate and decrease in temperature. It was found that a more homogeneous structure is observed with an increasing number of MAF cycles and the strain rate strain. Furthermore; the average grain size reduced from 850 nm to 220 nm after three cycles of MAF. Finally; experimental work was performed to validate the results.

Comparison of Microstructure and Hardness of Pure Copper Fabricated by Multi-Axial Forging and Multi-Axial Diagonal Forging

Comparison of Microstructure and Hardness of Pure Copper Fabricated by Multi-Axial Forging and Multi-Axial Diagonal Forging

Microstructure and Quasi-Static Mechanical Behavior of Cryoforged AA2519 Alloy

In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-static loading were investigated to determine the influence of cryogenic forging on alloys’ subgrains dimensions, grain boundaries interactions, strength, ductility and toughness. In addition, the failure mechanisms at the tensile rupture surfaces were characterized using scanning electron micro-scope (SEM). The results show significant improvements in the strength, ductility and toughness of the alloy as a result of the cryogenic MAF process. The formation of nanoscale crystallite microstructure, heavily deformed grains with high density of grain boundaries and second phase breakage to finer particles were characterized as the main reasons for the increase in the mechanical properties of the cryogenic forged samples. The cryogenic processing of the alloy resulted in the formation of an ultrafine grained material with tensile strength and toughness that are ~41% and ~80% higher respectively after 2 cycles MAF when compared with the materials processed at ambient temperature. The fractography analysis on the tested materials shows a substantial ductility improvement in the cryoforged (CF) samples when compared to the room temperature forged (RTF) samples which is in alignment with their stress-strain profiles. However, extended forging at higher cycles than 2 cycles led only to increase in strength at the expense of ductility for both the CF and RTF samples.

Comparison Between Multi-Axial Forging and Multi-Axial Diagonal Forging of AA1100 Using Finite Element Analysis

Comparison Between Multi-Axial Forging and Multi-Axial Diagonal Forging of AA1100 Using Finite Element Analysis

The effect of strain rate under multiple forging on the mechanical and microstructural properties

The flow stress of aluminum alloy 6082M under cyclic, non-monotonic plastic deformation has been determined by multiaxial forging experiments, using the MaxStrain system on a Gleeble 3800 thermo-physical simulator. The simulations were done at ambient temperature with different strain rates of 0.1, 1.0 and 10 1/s. The plastic strain amplitude per forging pass was 0.4. The accumulated equivalent strain was around 4 in each forging simulation.For the mechanical modeling of the cyclic, non-monotonic plastic deformation characteristic of the forming process, a control program and measurement arrangements have been developed. These controlled the equivalent logarithmic strain and the equivalent strain rate implemented in each forming step. It was also suitable for measuring the dimensions of the deformed material volume between the tools. These parameters and the measured force data were applied in the mechanical model, based on the principle of virtual velocities.In parallel with the cyclic experiments, monotonic plane-strain Watts-Ford compression tests were also performed. Strain rate influence for material properties has been investigated. Monotonous and cyclic flow curves were compared, and significant differences were found. Contrary to the monotonous flow curve, the cyclic flow stress showed the Bauschinger effect, occurring when the load direction was changed. Concerning the effect of strain rate it can be concluded that the applied strain rate influences the strain hardening, the resultant hardness and the characteristic properties of the generated ultrafine-grained microstructure.

Effect of multiaxial cryoforging on microstructure and mechanical properties of a Cu-Ti Alloy

Cu-Ti alloy, processed by multiaxial forging (MAF) at cryogenic temperature with a cumulative strain up to 1.64, was investigated for microstructure and mechanical properties. The deformed microstructures were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The average grain size of 2 μm was achieved in the deformed sample after 3 cycles of MAF. TEM studies indicated that the shear bands width of the deformed sample after 3 cycles reduced to 1 μm. Tests for mechanical properties indicated an increase in tensile strength and hardness and it was found to be correlated with an increase in dislocation density and grain boundary strengthening mechanism. Ultimate tensile strength (UTS) of 390 MPa, 480 MPa, and 590 MPa was observed in MAF processed samples after 1, 2, and 3 cycles, respectively. Hardness increased from 65 Hv (as-received) to 240 Hv after 3 cycles of MAF. Fractography analysis showed that, with an increase in number of MAF cycles, dimple size reduced up to 1 cycle and percentage elongation increased after 2 cycles of MAF.

The Influence of Warm abc-Pressing on the Structure and Mechanical Properties of Stable Chromium-Nickel-Molybdenum Steel

The structure and properties of the 17Cr13Ni3Mo0.01C stable austenitic steel subjected to high-temperature plastic deformation by the abc-pressing (multiaxial forging) are investigated in the temperature range from 800 to 600°С. The results of investigations demonstrate that after the abc-pressing the steel has a single-phase austenitic ultrafine-grained structure with the size of its elements (grains and subgrains) of (200 ± 140) nm. The formation of the ultrafine-grained state increases the strength properties (0.2 proof stress increases threefold) and decreases the elongation value of the steel at room temperature compared to the coarse-grained specimens. An analysis of the contributions from hardening during abc-pressing evidences in favor of the strength improvement being primarily due to the grain refinement; it is well described by the Hall–Petch relationship. In this case steel with ultrafine-grained austenitic structure exhibits an effect of structural superplasticity at the temperatures T > 750°С: the elongation value at Т = 800°С is found to be 180%.

Ductility enhancement in Mg-0.2%Ce alloys

Ductility of Mg alloys can be enhanced by alloying, controlling the grain size and randomizing the texture. In this study, Mg-0.2%Ce alloys were processed using rolling, multi-axial forging (MAF) and equal channel angular pressing (ECAP) to fabricate three different textured samples from the same alloy. The samples were further annealed to produce similar grain size without altering texture. Rolled sample had a strong basal {0001} texture, the MAF sample developed a weak {011¯2¯} [2¯31¯2] texture component in addition to the basal texture and the ECAP sample exhibited a strong non-basal {1¯21¯3} [2¯111¯] texture component. The tensile properties, texture evolution and relative slip/twin activities in the samples were investigated experimentally and numerically. The tensile yield strength, ultimate strength and uniform elongation of the rolled, MAF and ECAP samples were 110MPa, 250MPa, 17%; 60MPa, 200MPa, 30% and 55MPa, 250MPa and 40%, respectively. The non-basal texture components in ECAP and MAF samples favored the formation of extension twins and pyr. <c+a> slip during tensile loading. Full field crystal plasticity finite element modelling (CPFEM) using the initial texture of the materials as input provided insights into the activation of different deformation modes and observed differences in hardening mechanisms as well as strain localization and premature failure of the rolled samples. CPFEM analysis confirms that Ce addition reduces the relative values of the critical resolved shear stress (CRSS) for the slip and twinning systems which, in turn, allows for texture modification during material fabrication. These, combined with the ability to control grain size in MgCe alloy with excess Ce, provide options for ductility enhancement in Mg alloys.

Elevated corrosion in strain hardened Al[sbnd]Mg alloy

Al-4.17 Mg (Al 5080) alloy was processed by multi axial forging (MAF) at room temperature up to cumulative strain of 4.2 in the present work. Mechanical properties of the alloy were investigated through Vickers hardness test and tensile test. Corrosion studies were carried on standard, forged and forged & annealed samples using 3.5% NaCl solution employing both Potentiodynamic polarization and immersion method. Microstructural evolution was studied on all the three samples using characterization techniques such as optical microscopy, electron backscattered diffraction, scanning electron microscopy and transmission electron microscopy. On a sample subjected to MAF, improvement in the strength and hardness was observed along with the significant drop in the corrosion resistance. However, when the same sample was further annealed, corrosion resistance was not only retained, but improved drastically. This odd behavior of this alloy was never reported earlier. The improved corrosion resistance of this alloy was discussed in light of surface profile along with the microstructural features.

Structure and Properties of Ti/TiB Metal-Matrix Composite after Isothermal Multiaxial Forging

Structure and Properties of Ti/TiB Metal-Matrix Composite after Isothermal Multiaxial Forging

Evolution of microstructure and mechanical properties of Ti/TiB metal-matrix composite during isothermal multiaxial forging

Mechanical behavior and microstructure evolution of a Ti/TiB metal-matrix composite during multiaxial forging (MAF) at 700 and 850 °C and a strain rate 10−3 s−1 were studied. The composite was produced via in-situ 3Ti + TiB2→2Ti+2TiB reaction during spark plasma sintering at 1000 °C. Mechanical behavior in terms of aggregated σ-Σε curves during MAF at both temperatures demonstrated a pronounced softening following by a steady-like flow stage. Microstructure evolution during MAF at both temperatures was associated with (i) dynamic recrystallization of the titanium matrix and the formation of dislocation-free areas of ∼1 μm in diameter and (ii) shortening of TiB whiskers by a factor of ∼3. MAF at 700 and 850 °C to cumulative strain ∼5.2 resulted in a considerable increase in the low-temperature ductility without substantial loss in strength. Contributions of different strengthening mechanisms into the overall strength of the Ti/TiB metal–matrix composite were discussed.

Substructure Development and Deformation Twinning Stimulation through Regulating the Processing Path during Multi‐Axial Forging of Twinning Induced Plasticity Steel

Multi‐axial forging (MAF) at room temperature is employed to investigate the effects of deformation processing path and the amount of imposed strain on the deformation mechanisms of a twinning‐induced plasticity (TWIP) steel. The results indicate that the twin frequency is decreased by applying the 2nd compression (∑ɛ = 0.8), however, an unexpected increase is realized at the end of first MAF pass (∑ɛ = 1.2). This is attributed to the change in strain path and orientation dependence of deformation twinning. The latter is phenomenal considering the previous researches reporting the suppression of twinning at the early stage of deformation (ɛ &lt; 0.4). The same sequence is followed during the second pass of MAF process. Interestingly, the progressive and continues substructure development along with dynamic Hall–Petch effect results from deformation twinning leads to an appreciable grain refinement. The latter is accompanied by the sharp drop of hardening rate in corresponding flow curves. The microtexture analysis indicates the strengthened texture of the 1 pass‐processed specimens which is weaken at the end of 2 pass due to the recrystallization and increasing the number of texture component. The current work also explores the room temperature mechanical properties of the multi axial forged workpiece through elaborating the miniaturized tensile testing method.

Investigation of microstructure and mechanical properties of the Cu–3% Ti alloy processed by multiaxial cryo-forging

Abstract

Influence of Multi Axial Forging (MAF) on Microstructure and Mechanical Properties of Cu-Ti Alloy

Multi axial forging (MAF) is one among the severe plastic deformation (SPD) processes, where large strains are imposed into the component. In the present work, as-received Cu-1.5%Ti alloy was subjected to MAF for 2 and 4 cycles at room temperature. Microstructure showed grain refinement after 2 and 4 cycles. Average grain size obtained for MAF processed samples after 2 and 4 cycles are 120 µm and 40 µm, respectively compared to initial grain size of 800 µm. The Mechanical properties were analyzed for as-received and MAF processed samples. Tensile test showed increased ultimate tensile strength (493 MPa) for MAF 4-cycle sample compared to as-received (191 MPa) condition with accumulated strain of 2.18 for 4 cycles. Increase in hardness was observed for MAF processed sample of 143 Hv for 4-cycle compared to as-received sample of 67 Hv

Aluminum based Composites by Severe Plastic Deformation Process as New Methods of Manufacturing Technology

Composites a material was developed to replace metal and alloys, because of the properties such as light weight and unique mechanical properties. Processing of aluminum-based composites has been developing by new manufacturing technology, namely severe plastic deformation (SPD), to produce unique of mechanical properties. Some of the methods used are; equal channel angular pressing (ECAP), accumulative roll bonding (ARB) and multi-axial forging (MAF). The results of some of these methods were compared with the latest method of new SPD, namely: repetitive press roll forming (RPRF). Based on grain morphology and mechanical properties, the result of RPRF has superior to another method. The properties produced by SPD technology was varies, the highest of hardness produced by RPRF process was 88 HV10, ECAP produced 65 HV10, MAF was 46 HV10 and ARB reached 50 HV10. While the highest of tensile strength produced by MAF was 237 MPa while the RPRF process just only around 147 MPa, but the ultrafine grains just only produced by RPRF method which is 0.9 μm, compared to other methods: MAF 1.2 μm, ECAP 5.7 μm and ARB is not so far with MAF that is equal to 1.4 μm. The RPRF process can be recommended for the interest of the aluminum-based composite materials processing industry. Because currently some component product by industries have been substituted from metal alloy materials to metal-based composites.

Effect of High Strain Rolling and Multiaxial Forging on Tensile and Fracture Behaviour of ZE41 Magnesium alloy

The present work is focused to study tensile and fracture strength of severely plastically deformed ZE41 Mg alloy and correlate it with the microstructural characteristics of deformed samples. Two types of severe plastic deformation (SPD) were performed such as high strain rolling (75% HSR) and multiaxial forging (6 Pass Forged) followed by high strain rolling (75%HSR). The tensile and fracture properties of deformed samples were compared with as received (AR) and solution treated (ST) samples. The 6 pass forged followed by 75% HSR (6PF75HSR) sample has shown maximum yield strength (YS) and ductility (%E), 250 MPa and 17%, respectively. However, ultimate tensile strength (UTS) of both the SPDed samples was found to be 315 MPa. The fracture toughness (J1C) and hardness of 75%HSR were slightly superior to 6PF75HSR i.e. 11.4 kJ/m2 and 76 HV, respectively. The high tensile and fracture strength of the processed Mg alloy are due to its fine grain size and high dislocation density. The microstructural features characterized by optical (OM) and scanning electron microscopy (SEM) are used to elucidate the improved strength of the processed alloy. The grain refinement was evident from the transmission electron microscopy (TEM) results.

Misorientation distribution of high angle boundaries formed by grain fragmentation: EBSD-based characterization and analysis performed on heavily deformed iron

When studying crystal lattice fragmentation during plastic deformation of metals, it is of great importance to characterize high angle deformation-induced boundaries as long as their creation and evolution controls grain refinement. A problem exists however to separate a contribution of DIBs to overall misorientation distribution from a contribution of original grain boundaries, particularly when total lengths of high-angle deformation-induced and original grain boundaries are comparable. In the present study, a method making possible this separation based on electron backscattering diffraction is suggested and used to characterize evolution of deformation-induced boundary misorientations in polycrystalline iron deformed under various conditions. The method is shown to provide reasonable accuracy up to a strain of ~ 2 in the case of uniaxial compression and up to a strain of 5 in the case of multi-axial forging. It has been shown that character of the deformation-induced boundaries evolution in iron changes weakly when increasing deformation temperature from room temperature to 400C. At the same time, this evolution differs significantly in iron deformed by uniaxial compression and multi-axial forging. In all cases considered in the present study a deformation-induced boundary misorientation distribution can be represented as a superposition of three partial distributions. The first two partial distributions correlate with those obtained earlier in transmission electron microscopy studies. The third partial distribution suggested in the present study describes the highest-angle part of deformation-induced boundary misorientation distribution. Each partial distribution evolves according to its own law with proceeding deformation.