Multiaxial Forging Research Articles

Investigations of microstructure, impact toughness, and fatigue failure behavior of bulk UFG Al–Li 8090 alloy processed by multi-axial forging

Investigations of microstructure, impact toughness, and fatigue failure behavior of bulk UFG Al–Li 8090 alloy processed by multi-axial forging

On the microstructure, texture and electrochemical properties of severely deformed and artificially aged lightweight AA2050 Al–Cu–Li alloy

Lightweight 3rd generation Al–Cu–Li alloy AA2050 was severely deformed via Multi Axial Forging (MAF) at 170 °C followed by artificial aging at 150 °C. Effect of MAF and post MAF aging on microstructure and precipitation was investigated using transmission electron microscopy (TEM). Formation of deformation bands and large dislocation cells were evident on MAF processed samples. Post MAF peak aging resulted in the distribution of fine T1 precipitates in grain interiors with reduction in grain boundary precipitation. Bulk texture studies reveal the formation of strong Goss and S texture components upon MAF processing. Further, low temperature artificial aging doesn’t exhibit significant changes in texture characteristics, either in terms of texture intensities or texture components. Polarization studies showed that peak aged samples exhibited better corrosion resistance compared to un-aged samples. Overall, 12 pass MAF processed and peak aged samples showed higher corrosion resistance. Further, corrosion surface morphologies examination revealed the change in corrosion mechanisms with thermomechanical treatments. Improved corrosion resistance after MAF and peak aging widens the requirements in aerospace and aircraft applications for such engineering alloys.

Optimization of wire electrical discharge machining parameters of AA6063/Al2O3 nanocomposite processed by multi axial forging using Taguchi technique

AbstractThe aluminium based matrix composites have excellent mechanical properties to use in automobile, aerospace, aviation, and military industries. The aluminium based matrix composite possesses desired characteristics like specific strength, excellent rigidity and wear resistance. The stir casting technique was used to fabricate the nanocomposite of AA6063 alloy reinforced with 5 weight % nano aluminium oxide particulate. To improve the microhardness of as cast and aluminium based nanocomposites, multiaxial forging was performed up to three passes for grain refinement. Wire electrical discharge machining was used to machine both as cast and “AA6063/Al2O3” (zero and three multi axial forging pass). The machining characteristics of samples were statistically examined using the Taguchi technique. The material removal rate in three multiaxial forging pass nanocomposite sample increased as peak current increases. However, increasing the pulse off time resulted in the lowest material removal rate. The surface roughness was found to be higher in the nanocomposite sample in comparison to as cast. The machining on nanocomposite multiaxial forged sample has a greater impact as compared to as cast. After machining, scanning electron microscopy was used to examine the surface morphology. The presence of different elements in the castings was validated using energy dispersive X‐ray spectroscopy.

Fabrication of wear resistant nanocomposite and its mechanical properties: A step towards sustainability

AbstractNowadays, particulate reinforced aluminium composites are appealing structural materials for numerous applications, such as automotive and aerospace, due to their low weight and high specific strength. Nanocomposite morphology and interfacial properties may alter when nano sized particles are reinforced with an aluminium matrix. The addition of nano reinforcement of aluminium oxide particle improve the mechanical strength of base alloy and a further improvement in mechanical properties may be enhanced by grain refinement processed under multi axial forging technique. The present study demonstrates the synthesis of wear resistant nanocomposite. It also investigates the effect of multi axial forging on microstructure, mechanical properties and wear behaviour of aluminium based nanocomposite. Optical microscopy and electron backscatter diffraction techniques were used for microstructural characterization. The fractography and worn surface analysis were examined by using scanning electron microscopy. Energy dispersive X‐ray spectroscopy is used to show the presence of nanoparticles in casting. After three multi axial forging passes, the average grain size was reduced up to 4.2 μm as cast and 1.15 μm in nanocomposite. The wear resistance, microhardness and tensile strength of multi axial forging processed nanocomposite were significantly improved. All improved mechanical and wear properties cause the material one step towards sustainability.

Understanding the weakening of texture in multiaxial forged ultrafine-grained strong and ductile Mg-2Zn-2Gd alloy

ABSTRACT Texture is an important aspect that impacts the formability of magnesium (Mg) and its alloys. Recently, the unique characteristics of multiaxial forging of Mg-2Zn-2Gd alloy were discussed, where it was demonstrated that multiaxial forged processed alloy is characterized by high strength and high ductility combination and the texture is significantly weakened or almost texture-free. The objective of the study described here is to obtain some fundamental insights that explain the underlying reasons for the weakening of texture in the multiaxial forged Mg-2Zn-2Gd alloy.

Evolution of Microstructure and Mechanical Properties of Ti-6Al-4V Alloy under Heat Treatment and Multi-Axial Forging.

The mechanical properties of various Ti-6Al-4V alloys are influenced by their respective microstructures. This study generated an ultrafine-grain (UFG) Ti-6Al-4V alloy featuring bimodal grain distribution characteristics achieved through initial heat treatment, multi-axial forging (MF), and annealing. The study also extensively examined the evolution process of the alloy's microstructure. By subjecting the materials to heat treatments at 900 °C with air cooling and 950 °C with air cooling, both materials were found to be consisted of primary α (αp) and transformed β (αs+β) regions with different proportions. Following MF, the sample treated at 900 °C displays a microstructure featuring UFGs of α+β surrounding larger micron-sized αp grains. On the other hand, the sample treated at 950 °C displays a microstructure distinguished by twisted αs lamellar and fragmented β grains surrounding larger micron-sized αp grains. Following annealing, no significant grain growth was observed in the sample. The geometrically necessary dislocations (GNDs) within the UFGs were eliminated, though some GNDs persisted within the αp grains. The samples undergoing the 900 °C heat treatment, MF, and subsequent annealing exhibited elevated strength (1280 MPa) and total elongation (10.7%). This investigation introduces a novel method for designing the microstructure of the Ti-6Al-4V alloy to achieve superior performance.

Microstructural Evolution and Mechanical Behavior during Isothermal Multiaxial Forging of Nickel-Based Superalloy SUPERNI 718

Microstructural Evolution and Mechanical Behavior during Isothermal Multiaxial Forging of Nickel-Based Superalloy SUPERNI 718

A modified Johnson-Cook model to determine plastic flow behavior of Fe-30Mn-9Al-0.8 C low-density steel during warm multiaxial forging

The microstructural changes in Fe-30Mn-9Al-0.8 C low-density steel upto equivalent strain 2.3 during multiaxial forging (MAF) and their impact on tensile strengthening have been thoroughly investigated. The processed sample at 0 pass, 1 pass, 3 pass, and 5 pass with 33% normal strain in each pass are characterized by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The analysis of XRD confirms a noticeable increase in dislocation density progressing from 0.79 × 1015 m−2 to 8.98 × 1015 m−2, attributed to a decrease in crystallite size and an increase in microstrain from 3.66 × 10−3 to 6.8 × 10−3. The grain size reduces from 50 μm to 13 μm. The yield strength increases from 380 MPa to 1528 MPa, while the ultimate strength increases from 762 MPa to 1548 MPa after 5 passes. It is observed here that both dislocation density and grain boundaries contribute to strengthening the material. However, up to three passes, dislocation strengthening is significant. Additionally, a numerical framework is developed to model the evolution of dislocation density, grain size and yield strength at each stage of MAF. To emphasize the role of strengthening parameters in predicting the flow stresses in every MAF pass accurately, a material VUMAT subroutine in ABAQUS has been created for a modified Johnson-Cook (J-C) constitutive model that accounts for the role of increased dislocation density and grain size. The developed model demonstrates its capability to accurately capture essential material features, including equivalent strain, dislocation density, and grain size. Furthermore, it exhibits the ability to predict the yield strength approximately following each MAF pass.

Wear mechanism transforming of ultrafine-grained pure titanium by multi-axial forging and low-temperature annealing

The effect of microstructure and mechanical properties of submicro grained commercial pure titanium (CP–Ti) on the wear mechanism is still unclear. In the present work, CP-Ti samples were subjected to multi-axial forging (MAF) and low-temperature annealing treatment to prepare ultrafine-grained (UFG) material. The mechanical properties, microstructure, and tribological characterization between coarse-grained (CG) sample and UFG samples were comparatively studied. The results showed that the MAF sample could reach a grain size of 165 nm, while its grains coarsened slightly after low-temperature annealing. The MAF sample had the highest strength and hardness and the lowest coefficient of friction, but only a 7.3 % decrease in wear rate compared to the CG sample. The 400 °C annealed MAF sample possessed a good combination of tensile strength (814 MPa) and elongation (18.6 %), resulting in the lowest wear rate of 16.8 × 10−5mm3/(N∙m). The dominated wear mechanisms of the CG sample, MAF sample and 500 °C annealed MAF sample were abrasive wear, adhesive wear and delamination wear, while the primary mechanism of the 400 °C annealed MAF sample was abrasive wear and adhesive wear. It was found that the wear mechanism transforming, higher hardness and sufficient work hardening could be responsible for lower wear rate of the 400 °C annealed MAF sample. The 400 °C annealed MAF sample showed a thinner and more homogeneous deformation layer near the worn surface, and its thickness of deformation layer was about 8 μm.

Investigation of the Effects of Various Severe Plastic Deformation Techniques on the Microstructure of Laser Powder Bed Fusion AlSi10Mg Alloy

In this paper, we present a complete characterization of the microstructural changes that occur in an LPBF AlSi10Mg alloy subjected to various post-processing methods, including equal-channel angular pressing (ECAP), KoBo extrusion, and multi-axial forging. Kikuchi transmission diffraction and transmission electron microscopy were used to examine the microstructures. Our findings revealed that multi-axis forging produced an extremely fine subgrain structure. KoBo extrusion resulted in a practically dislocation-free microstructure. ECAP processing at temperatures between 100 °C and 200 °C generated moderate grain refinement, with subgrain diameters averaging from 300 nm to 700 nm. The obtained data highlighted the potential of severe plastic deformation as a versatile method for tailoring the microstructure of the AlSi10Mg alloy. The ability to precisely control grain size and dislocation density using specific SPD methods allows for the development of novel materials with ultrafine-grained microstructures that offer the potential for enhanced mechanical and functional properties.

Severe Plastic Deformation of Mg–Zn–Zr–Ce Alloys: Advancing Corrosion Resistance and Mechanical Strength for Medical Applications

Magnesium-based alloys hold potential for medical applications, but face challenges like rapid bioresorption and limited mechanical strength during early bone healing. In our study, we present a novel Mg–Zn–Zr–Ce alloy with low cerium content (up to 0.1 wt.% Ce) processed using two severe plastic deformation (SPD) techniques. Through an innovative combination of multiaxial forging and multipass rolling, we have achieved a fine-grained structure with an average grain size of the primary α-Mg phase of 1.0 μm. This refined microstructure exhibits improved mechanical properties, including a substantial increase in yield strength (σYS) from 130 to 240 MPa, while preserving ductility. The alloy’s composition includes α-Mg grains, cerium and zinc hydrides, and intermetallic phases with cerium and zinc elements. Tensile testing of the fine-grained alloy demonstrates an enhancement in yield strength (σYS) to 250 MPa, marking a 2.8-fold improvement over the conventional state (σYS = 90 MPa), with a modest 2-fold reduction in ductility. Crucially, electrochemical tests conducted in physiological solutions highlight substantial advancements in corrosion resistance. The corrosion current was reduced from 14 to 2 μA/cm2, while polarization resistance decreased from 3.1 to 8.1 kΩ∙cm2, underlining the alloy’s enhanced resistance to biodegradation. Our results show that the novel Mg–Zn–Zr–Ce alloy, after combined SPD, demonstrates mitigated bioresorption and enhanced mechanical properties. Our findings highlight the fact that the introduction of this innovative alloy and the application of SPD represent significant steps towards addressing the limitations of magnesium-based alloys for medical implants, offering potential improvements in safety and effectiveness.

Effect of Strain Per Pass on Microstructure and Mechanical Properties of Multi-Axially Forged Cast AA5083 Alloy at Room Temperature

This paper investigates the effect of strain per pass over a cycle on, multi-axially forged cast AA5083 alloy at room temperature. To begin with, Multi-Axial Forging (MAF) with two different strains per pass was imposed on the alloy without changing the die geometry. Samples were deformed to cumulative strains of Σɛ = 2.46 (2 Cycles) and Σɛ = 2.79 (3 Cycles), with two different strains per pass ε = 0.41 and ε = 0.31 respectively. Microstructural analysis was carried out by using OM, XRD, and SEM with EDS. Structural changes were characterized, and it was revealed that grain fragmentation was caused by the frequent development of deformation and micro shear bands, which was followed by the evolution of new fine grains in the original grain structure. Mechanical properties were evaluated by tensile, and hardness tests. MAF of ɛ = 0.41 per pass results in high tensile strength and hardness, 428 MPa and 147 Hv; respectively at a cumulative strain of Σɛ =2.46. Processing with strain ɛ = 0.31 per pass produced strength of 380 MPa and hardness of 131 HV after cycle III with a cumulative strain of 2.79. MAF of strain ɛ = 0.41 per pass with cumulative strain of 2.46 resulted in a higher grain refinement structure with increased strength compared to a strain of 0.31 per pass with a cumulative strain of 2.79. Therefore, with the imposition of the high strain per pass produced more grain refinement and consequently higher strength.

Microstructures and Mechanical Properties of Al-Zn-Mg-Cu Alloys under Multi-Directional Severe Strain and Aging.

Microstructure is a significant factor that influences the mechanical properties of alloys. The effect of multiaxial forging (MAF) and subsequent aging treatment on the precipitated phases of Al-Zn-Mg-Cu alloy remains unclear. Therefore, an Al-Zn-Mg-Cu alloy was processed by means of solid solution and aging treatment, and MAF and aging treatment in this work, and the composition and distribution of precipitated phases were characterized in detail. The MAF results for dislocation multiplication and grain refinement were found. The high density of dislocation greatly accelerates the nucleation and growth of precipitated phases. Thus, the GP-zones almost transform into precipitated phases during subsequent aging. The MAF and aging alloy has more precipitated phases than the solid solution and aging treated alloy. The precipitates on the grain boundary are coarse and discontinuously distributed due to dislocation and grain boundary promoting the nucleation, growth and coarsening of the precipitates. The hardness, strength, ductility and microstructures of the alloy have been studied. Without compromising the ductility much, the MAF and aging alloy has higher hardness and strength, with values of 202 HV and 606 MPa, respectively, and an appreciable ductility of 16.2%.

Tribological studies on aluminum beryl composites subjected to ECAP process

The strengthening processes of aluminum alloys and their composites are generally assessed after precipitation hardening or following different laid down strain hardening procedures such as Equal Channel Angular Pressing (ECAP), Multi-Axial Forging (MAF), High-Pressure Torsion (HPT), Accumulative Roll Bonding (ARB), etc. Among them, ECAP is considered to be a novel method of producing fine-grained structure with different properties. On-going through the available literature, it is noted that the adoption of ECAP in Aluminum metal matrix composites, especially the Aluminum Beryl composites and then assessing their tribological responses, are scarce to come across. Hence, this particular aspect is addressed in this work.In the present investigation, Al 2024 alloys containing 6% Beryl particles, produced by stir cast route and subjected to ECAP operation up to two passes, have been assessed for slide wear and coefficient of friction (CoF) properties for comparison with un-reinforced Al 2024 alloy for qualitative and quantitative evaluation purposes. The wear and friction evaluation are carried out using the well-known Pin-On-Disc (POD) apparatus for three different loads (49 N, 91 N, and 136 N) and sliding distances (2000, 4000 and 6000 m) at a constant sliding speed of 1.67 m/s.The data reveals that the wear loss decreases with increase in the number of passes due to increase in hardness & decrease in grain size for all the three loads and sliding distances employed. Further, the wear losses show an increasing trend with an increase in the applied load. Also, it is observed that the CoF decreases with increase in number of passes at all loads. It is high in the as cast state and it increases with increase in load. It is inferred from the present findings that the ECAP has made a significant impact on the wear behaviour of Al-Beryl composites, thus emphasizing the fact that the composites are suited for wear resistance applications such as in production engineering sectors.

Enabling manufacturing of multi-axial forging-induced ultrafine-grained strong and ductile magnesium alloys: a perspective of process-structure-property paradigm

ABSTRACT Magnesium (Mg) alloys are difficult to cold/warm-process due to their hexagonal close-packed (HCP) lattice, which has restricted slip systems and makes plastic deformation at low temperatures a challenging task. Multi-axial forging (MAF) and annealing of as-cast alloys were combined to create a texture-free ultrafine-grained (UFG) structure with a high strength-high ductility combination to address this challenge. The study showed a clear and fundamental change from basal and pyramidal dislocation slip to twinning in the strong and ductile UFG Mg alloy compared to the low strength coarse-grained (CG) Mg alloy counterpart. This implied that the dislocation activity, grain orientation, and particular grain boundary states played an important role in controlling the deformation mechanisms. The potential impact of processing Mg alloys by MAF opens-up a new frontier of strong and ductile low-density materials for light and efficient solutions including energy absorption and formability and provides a perspective in terms of process-structure-property relationship.

Improved structural uniformity and specific strength of commercially pure aluminum through variable temperature multi axial forging: Finite element analysis and experimental study

Multi axial forging (MAF) is a forging-based severe plastic deformation (SPD) technique which is prominently used to refine grain structure and improve the strength of the material. While the advantages of MAF lie in its simple tool design and ability to process bulk materials, the main limitation is the inhomogeneity in the generated microstructure across the cross-section at initial passes. Increasing the number of MAF passes may partially help to solve the problem, but arbitrary increase in the number of passes may lead to redundant increase in manufacturing cost and time. The current work proposes a manufacturing strategy for MAF to achieve homogeneous microstructure with uniform grain refinement by using reduced number of MAF passes. To achieve structural uniformity within fewer MAF passes, a controlled thermo-mechanical based optimum MAF process strategy is developed on a commercial pure Al through the finite element analysis (FEA) simulation and the same is validated experimentally. The manufacturing strategy resulted significant grain refinement via simultaneous action of continuous dynamic recrystallization and geometric dynamic recrystallization with microstructural homogeneity which caused a significant improvement in tensile properties (more than two times than the base) with considerable ductility (more than 25%) and isotropy property across the thickness. The scientific knowhow has been established via processing–structure–property correlation-ship.

β Grain Size Inhomogeneity of Large Scale Ti-5Al-5V-5Mo-3Cr Alloy Bulk after Multi-Cycle and Multi-Axial Forging in α + β Field

In order to fabricate homogeneous large-scale Ti-5Al-5V-5Mo-3Cr (Ti-5553) alloy bulk with fine and equiaxial β grain, we performed a series of multi-axial α + β field forging with 62 forging cycles on the large-scale Ti-5553 billet by using 12.5 MN high-speed hydraulic press. The β-annealed microstructure was the starting microstructure of the billet. After the 6th forging cycle, β grain deformed dramatically, and the grain-boundary network developed within the irregular β grain. As the forging cycle increased to 44, the volume fraction of the fine and equiaxial β grain that is less than 20 μm, which is caused by dynamic recrystallization, increased gradually. However, the incomplete dynamic recrystallization region within the original β grain could not be eliminated. As the forging cycle further increased, the volume fraction of the fine and equiaxial β grain did not increase. In contrast, the abnormal grain growth of the β phase occurred during 50th~62nd forging cycle. Here, we attribute the formation of the incomplete dynamic recrystallization region and the abnormal grain growth of the β phase to the high deformation rate of the α + β forging. The refining behavior of β grain and the abnormal coursing β grain, which is found during the multi-cycle multi-axial forging of large-scale Ti-5553 alloy billet, are seldom reported in the isothermal compression of small-scale Ti-5553 alloy specimen. The findings of the paper are instructive for improving the sub-transus forging strategy that is used to fabricate the large-scale homogeneity Ti-5553 alloy billet with fine and equiaxial β grain.

Evolution of dislocations and grain boundaries during multi-axial forging of tantalum

Presented here is the evolution of microstructure of Ta during multi-axial forging, with a specific understanding of how grain boundary movement and their interaction occurs during deformation. Coarse grained (CG) tantalum was multi-axially forged till 3, 6, and 9 passes in a closed channel die to refine grain size and increase its strength. The grain size was refined from 64 μm to 760 nm, the dislocation density increased by an order of magnitude, the Vickers hardness increased from 92 to 223 HV, and the yield strength at room temperature increased from 178 to 653 MPa. It was found that the contribution of GBs to strengthening was higher than that of dislocations. Mechanisms for GB structure evolution during deformation were studied using molecular dynamics (MD) simulations. GB mobility was high for low angle GBs (LAGBs) and reduced with increasing tilt angle, after which it took on low values for high angle GBs (HAGBs). The mobility of specific HAGBs were due to the formation of ledges/disconnections and dissociation into other GB types. MD results showed that the decrease in fraction of HAGBs during initial deformation can be attributed to the dissociation of HAGBs with low mobility into GBs with higher mobility.

Effect of interlamellar spacing on strength-ductility combination of β-solidified γ-TiAl based alloy with fully lamellar structure

The paper reveals the possibility for obtaining excellent strength-ductility combination under both tension and compression in a fully lamellar β-solidified γ-TiAl based alloy by controlling the interlamellar spacing. Ingots of the alloy were subjected to multi-axial forging, quenching and further aging at 800–1050 °C to produce microstructures with the colony size of 25 μm and interlamellar spacing (λ) in the range from 10 to 1500 nm. A good balance between ductility and strength was found at λ ∼100 nm under both tension (elongation to fracture of 2.9%; ultimate strength - 875 MPa) and compression (peak strain and stress of 39% and 2700 MPa, respectively) due to a strain transfer by transverse twin/slip bands that improved strain hardening capacity. Both coarser and thinner lamellae caused pronounced strain localization and early crack nucleation resulting in failure. Meanwhile, the Hall-Petch relationship was observed between the yield strength and interlamellar spacing above λ ∼20–50 nm. At a lower interlamellar spacing the yield strength stabilized at the values of 820 and 1150 MPa upon tensile and compression loading, respectively. The dependences of deformation and fracture mechanisms on the interlamellar spacing and loading scheme are discussed.

Strong and ductile texture-free ultrafine-grained magnesium alloy via three-axial forging

We describe here the ingenious concept of combining annealing of as-cast alloy with multi-axial forging (MAF) (forging along x, y, and z-directions) that was applied to thermo-mechanically process a lean magnesium-rare earth alloy and obtain high strength and high ductility combination. This approach interestingly led to texture-free ultrafine-grained (UFG) structure with high yield strength of ∼227 MPa and elongation of ∼30 %. The objective of the study is to describe the preliminary findings and elucidate the evolution of texture in the MAF alloy in conjunction with the microstructure and mechanical properties. The discovery of the contribution of MAF in influencing texture, microstructure and mechanical properties is important from the perspective of current challenge in the processing of Mg alloys that has a hexagonal close-packed (HCP) lattice with limited slip systems, which makes it difficult to thermo-mechanically process at low temperatures.