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In this work, effect of multi-axial room temperature forging process on scratch and wear characteristics of Al-7.3 and Al-12.1Si alloys with varying cumulative strains was investigated. Al-7.3 and Al-12.1Si alloy ingots were remelted in a furnace and then poured into a preheated die to produce a cast sample of the desired shape and dimension for the MAF process. These samples were subjected to solution heat treatment before forging Scratch test was conducted to measure the scratch resistance of unprocessed and MAF-processed samples. Dry sliding wear tests were performed on a tribometer (pin-on-disk) at ambient temperatures. MAF-processed materials exhibited better scratch and wear resistance compared to as-cast materials. After MAF, wear mechanisms in both alloys shifted from adhesive and delamination wear to a combination of abrasive and a lesser amount of adhesive wear. Moreover, the degree of delamination significantly decreased after MAF-process. Improved scratch and wear resistance is mainly due to increased microhardness via refinement and improved uniformity in the redistribution of eutectic silicon as well as the strain hardening of the aluminum phase. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

In this study, the deformation bands (DBs) in AA1100 after plane forging (PF) and return-plane forging (R-PF) during multi-axis diagonal forging (MADF) were observed using microtexture analysis. Typical texture components (plane-strain texture components) observed in face-centered cubic (FCC) materials deformed by plane-strain compression were developed in the PF specimen. Blurry bands with an orientation relationship of mainly LAGBs were developed in the deformed grains in the PF specimen. Slip trace analysis and Schmid factor (SF) calculations revealed the correlation between the blurry bands and the slip behavior. Regions of matrix and DBs inside the deformed grains of the R-PF specimen were distinguished mostly by their HAGBs. The heterogeneity of the Taylor factor (M) values that occurred within the blurry bands and their surrounding regions induced the development of the DBs in the R-PF specimen. The heterogeneities of the deformation behavior between the inside and the outside of the blurry bands that developed in the grains of the PF specimen during the R-PF were a direct reason for the generation of DBs in the deformed grains of the R-PF specimen. The transmission-EBSD (t-EBSD) technique revealed that the average misorientation angle inside the DBs was higher than that inside the matrix.

The effect of blocky to lamellar phase transformation on the microstructure and micro-texture of a Magnesium-Rare earth alloy containing long-period stacking order (LPSO) phases were examined comprehensively at the isothermal temperature of 400 °C via multiaxial forging. A very fine-grained microstructure with an average grain size of 1 μm was achieved after applying three multi-axial forging (MAF) passes. Particle stimulated nucleation (PSN) along with continuous dynamic recrystallizations (CDRX) due to the blocky LPSO phases were realized to be the main reasons for the achievement of such fine microstructure. The deformation-induced blocky to lamellar phase transformation began at 1/3 pass and expanded through the whole microstructure after the third pass. Such phase transformation was found to be initiated by the fragmentation of blocky phases. As a result of PSN and CDRX mechanisms, two new rare earth (RE) texture components of and || Transverse Direction (TD) were formed at the second MAF pass that led to a highly randomized deformation texture. Nevertheless, the continuous breakdown of blocky phases and their subsequent phase transformation to lamellar LPSO suppressed PSN at the third deformation pass. Hence, the formed RE texture components were disappeared which in turn increased the texture intensity at this deformation pass.

Two-way multi-axial forging was performed on a newly designed closed-die forging tool. The tool was operated on an MTS 810 material testing system. The connected computer recorded force and crosshead displacement as a function of time during operation. The sample material of the four-step forging experiment was CuE copper alloy. The plastic deformation was 0.8 per step, thus the rate of cumulative equivalent plastic strain was 3.2 by the end of the process. The speed of movement of the active tools during the whole test was 2 mm/min. Finite element simulation was performed with QForm3D software to investigate the force conditions of the process. The necessary flow curve was determined by Watts-Ford test. The force-displacement curves of the physical simulation were compared with the results of the finite element modeling. [ABSTRACT FROM AUTHOR]

The capability of multi-axial forging (MAF) as an efficient severe plastic deformation (SPD) method to improve the shape memory responses of a semi equiatomic NiTi alloy was investigated. The MAF cycles were performed at temperatures in two different ranges, where the governing deformation mechanisms were thought to be different. This was confirmed through the material corresponding true stress-true strain flow behaviors. The presence of different phases was traced by means of X-ray analysis. The martensitic transformation was hindered in the specimens deformed at 150 °C due to the presence of high dislocation density and in consequence the nano-crystalline austenite phase was the main phase after deformation. The specimens deformed at 400 °C however, experienced restoration phenomena thereby brought the martensite beside the austenite phase in the microstructure. The latter was related to shifting the transformation point to lower temperatures. The processed material at 400 °C exhibited both shape memory effect and super-elasticity due to the coexistence of restored and processed martensite and austenite phases. However the related recovery strain was reached to 3.2 pct. due to the corresponding shape memory effect. In addition, the results indicated that the multi-axial forging should be considered as a method to produce homogenous bulk NiTi alloy possessing an improved mechanical properties. To this end the microhardness, ultimate strength and elongation were improved from 220Hv, 920 MPa and 18.5% in as-hot rolled condition to ~590Hv, ~1700 MPa and 23% in optimum MAF condition scheme, respectively. [ABSTRACT FROM AUTHOR]

A magnesium alloy containing rare earth elements (Y and mish metals) was severely deformed through multi-axial forging (MAF) at 400 °C and the obtained microstructure, texture, and mechanical properties were characterized after applying successive MAF passes. The results showed that the volume fraction of the recrystallized grains was noticeably increased by increasing the MAF passes, where a homogeneous microstructure with a mean grain size of 4.8 μm was obtained after five MAF passes. A strengthened basal texture was developed after the first MAF pass. Further deformation to three and five MAF passes resulted in a texture weakening, where pyramidal planes tend to rotate parallel to the forging direction. The contribution of particle stimulated nucleation (PSN) was suggested to play an effective role in the texture weakening. The basal texture and grain refinement, which were achieved after applying one pass MAF, led to a combined improvement in strength and ductility, including 460 MPa ultimate strength and 12.4% ductility. As the number of deformation passes increased to three and five, the flow stress of the material was reduced, while the ductility considerably enhanced. The latter findings were discussed relying on the fact that the texture weakening after multi-pass MAF could make the deformation easier through activating more slip systems. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Multiaxial forging of tantalum increased the strength from 178 to 653 MPa. • Grain boundary (GB) spacing was reduced from 64 μm to 760 nm after 9 passes. • GBs contribute to yield strength than that of dislocations. • Mobility of low angle GBs are higher than that of high angle GBs. [ABSTRACT FROM AUTHOR]

In current investigation, effect of Multi-axial forging (MAF) processing temperature on microstructural evolution and mechanical properties of Al–Mg–Si alloy was investigated by performing MAF at (i) −147 °C (CT-MAF) and (ii) room temperature (RT-MAF). The electron Back scattered diffraction (EBSD) and transmission electron microscopy (TEM) were used for exploring the microstructural evolved. It was observed that MAF at −147 °C helped in accumulation of large amount of dislocations as confirmed from the TEM. The recovered, recrystallized, sub-grain and deformed grains were separated with the help of EBSD, using criteria based on grains orientation spread (GOS) and grain tolerance angle, and further correlated with the mechanical properties. The strong recrystallization texture (Goss texture ({110} <001>), and rotated Goss texture ({110} <110>)) were observed in CT-MAF sample as compared to RT-MAF sample. The average ultimate tensile strength and average hardness increased after the CT-MAF to 370 MPa and 124 VHN, respectively, almost average ultimate tensile strength (UTS) increased by 23% and average hardness increased by 33% as compared to RT-MAF sample. It was observed that at −147 °C processing temperature strain hardening mechanism was dominated in CT-MAF sample, whereas due to the room temperature processing temperature softening mechanism was dominated in RT-MAF sample. • Multiaxial forging (MAF) was performed on Al–Mg–Si alloy at (i) Room temperature (RT), (ii) −147 °C. • The recovered, recrystallized, sub-grain and deformed grains were separated through EBSD. • MAF at −147 °C and at (RT), strain hardening and softening mechanism were dominated, respectively. [ABSTRACT FROM AUTHOR]

• The formation mechanism of DBs observed in AA1100 after PF and R-PF during MADF was unraveled by microtexture analysis. • Calculation of the lattice rotation rate and the d i v g ˙ was used to evaluate the kinematic stability of deformed grains under the R-PF. • The heterogeneity of the orientation stability was used to explain the development of the DBs in the R-PF specimen. • CPFEM successfully simulated the development of DBs within deformed grains during the R-PF. • The heterogeneity of orientation stability occurring within the blurry bands enhanced the formation of DBs in the deformed grains during the R-PF. In this study, the formation mechanism of deformation bands (DBs) observed in AA1100 after plane forging (PF) and return-plane forging (R-PF) during multi-axis diagonal forging (MADF) was unraveled via microtexture analysis using a rate-sensitive model and crystal plasticity finite element method (CPFEM). Blurry bands with an orientation relationship of mainly LAGBs were developed in the deformed grains in the PF specimen. The heterogeneity of the orientation stability (Q) that occurred within the blurry bands and their surrounding regions contributed to the development of the DBs in the deformed grains in the R-PF specimen. Microstructure-based CPFEM successfully simulated the development of DBs within deformed grains during R-PF. CPFEM revealed that heterogeneity of the crystallographic orientation that occurred within the blurry bands and their surrounding regions inside the PF specimen was the main cause of the formation of DBs in the deformed grains during R-PF. Graphical Abstract [Display omitted]. [ABSTRACT FROM AUTHOR]

Abstract: The dynamic precipitation behavior during multi-axial forging in an Mg–7Gd–5Y–1Nd–0.5Zr alloy has been investigated and compared with that in static precipitation treatment. The results indicated that dynamic precipitation does occur during multi-axial forging. The dynamic precipitate can be deduced as β phase with face-centered cubic crystal structure (a = 2.22 nm). Most of the β precipitates locate at the dynamic recrystallization grain boundaries. The morphology and orientation relationship is different from that of the β phase formed in the static precipitation treated alloys, although the crystal structure is the same. The precipitation temperature of β phase during MAF is higher than that in the static precipitation treatment. [Copyright &y& Elsevier]

Abstract: Multi-axial forging of Al was carried out at room temperature in a confined channel die as a means of achieving severe plastic deformation (SPD). The microstructures of the 3, 6 and 9 pass samples were quantified using electron back scattered diffraction to obtain the distribution of boundary spacing and fraction of high angle boundaries. Subsequent compression tests at room temperature were carried out to determine their strength and strain rate sensitivity. Softening was observed beyond 6 passes both in terms of the pressing stress as well as the subsequent compression tests. Beyond 6 passes the fraction of high angle boundaries increased and the geometrically necessary dislocations (GND) density decreased. It was estimated that during SPD, Al had a higher hardening contribution due to GND and subgrain walls than that due to Hall–Petch type grain boundary strengthening. It was shown that as the fraction of high angle boundaries increased with increasing deformation, the dislocation strengthening term decreased and the Hall–Petch term increased, resulting in a net softening effect. [Copyright &y& Elsevier]

In the current work, open die multi-axial forging (MAF) of 6082 Al alloy was performed at room temperature. The resulting microstructure and mechanical properties were found to have a gradient from the periphery towards the center. The resulting inhomogeneity was quantified with the help of electron backscattered diffraction, X-ray diffraction analysis, hardness and tensile strength measurement. The recrystallized grains were found after the partition of inverse pole figure (IPF) maps by using the criteria (Grain orientation spread<1°& boundary misorientation angle>15°). The sub-grains were found by partition of the IPF-maps by using the criteria (Grain orientation spread>2° & 2° < Grain rotation angle<15°). The high driving force (dislocation density) available at center of the MAF sample was responsible for the increase in sub-grains size up-to micrometer regime as well as increase in the volume fraction of recrystallized grains. The presence of a strong deformation texture (Goss ({110} 〈001〉)) and the recrystallized texture (Rotated Cube texture ({001} 〈110〉)) were observed, as we proceed towards the center of the MAF sample. • Deformation gradient (surface to center) exits in the Multi-axial forged (MAF)-6082 Al alloy. • Recovery and recrystallization processes were more prone to center of the MAF-6082 Al alloy. • High dislocation density accumulated at the center of the MAF-6082 Al alloy. [ABSTRACT FROM AUTHOR]

The as-homogenized Al-5.5 Mg-0.3Mn-0.2Sc-0.1Zr alloy with average grain size of 60 μm and coherent Al 3 (Sc,Zr) precipitates of 5 nm in diameter was deformed to an accumulative equivalent strain (∑ε) of 7.02 by multi-axial forging (MAF) in channel die at room temperature. The mechanical property and microstructure of the as-homogenized (∑ε = 0), 3rd (∑ε = 2.34), 6th (∑ε = 4.68) and 9th pass (∑ε = 7.02) samples were investigated. Results show that dynamic recrystallization was inhibited due to the pinning effect of Al x Mn and Al 3 (Sc,Zr) precipitates. High density dislocation structure produced a remarkable strain hardening resulting a significant improvement of mechanical property at low equivalent strain (∑ε ≤ 2.34), while, the grain size changed little and the fine-grain strengthening effect was not obvious. Low-angle grain boundaries (LAGBs) formed gradually with increasing of equivalent strain as dislocation recombining, and developed into high-angle grain boundaries (HAGBs), resulting an obvious structure refinement at high equivalent strain. As a combined strengthening effect of strain hardening and grain boundary strengthening, the yield strength (YS) and ultimate tensile strength (UTS) increased to as high as 509 MPa and 597 MPa respectively when equivalent strain reached to 7.02. • High strength Al-Mg-Mn-Sc-Zr alloy was successfully produced by room temperature MAF process. • Recrystallization was inhibited by AlxMn and Al3(Sc,Zr) precipitates during MAF. • HAGBs increased with number of MAF passes and induced formation of fined-grain structures. • Mechanical property improvement is attributed to the combined effect of strain hardening and grain boundary strengthening. [ABSTRACT FROM AUTHOR]

A novel texture analysis approach is aimed to elucidate the role of strain path change in extending the superior strain hardening capacity of a twinning-induced-plasticity steel up to the large compressive imposed strains at room temperature, in lights of step-by-step texture modification. In this context, activation of different deformation mechanisms during multi-axial forging (MAF) process is fully studied using macrotexture and microtexture analyses by means of calculating Schmid factors of slip and twinning. Synergetic development of deformation twin and dislocation substructure throughout the 1st MAF pass leads to exponential strain hardening rate. This is correlated with the formation of texture components with twin-favoring (near to <001>) and slip-favoring (near to <111> and <110>) orientations in each compression of one MAF pass. Such cooperation can also be reached for larger imposed strains during the 2nd MAF pass at ∑Ԑ = 2.4. However, it results in a steady-state flow behavior through continuous dynamic recrystallization stemming from turning dislocation cells of slip-favoring grains into the new ultrafine grains. This is phenomenal as can be understandable by recognizing the orientation dependency of dislocation substructures including Taylor lattice and dislocation cells as representatives for deformation twins and cross-slip, respectively. Having grains with dislocation cell and Taylor lattice respectively is the origin of facilitating restoration-based process and twinning activation, which modifies the texture by developing a twofold configuration in the course of imposing strain path change. As the second phase of this study, a detailed analyzation of subsequent mechanical responses of MAFed materials is focused through the room-temperature tensile and compression testing methods with the emphasis on the effect of pre-test microtexture on asymmetrical behavior. The shear-punch test is also used to prove the positive effect of recrystallized grains to enhance the mechanical properties. Image 1 • Strain path change effect on texture evolutions during severe plastic deformation. • Texture tuning via twofold texture development favoring for slip and twinning. • Orientation dependent Taylor lattice and dislocation cell under large compressions. • Strain path change-driven room temperature continuous dynamic recrystallization. • Contribution of recrystallized grains in enhancing the mechanical properties. [ABSTRACT FROM AUTHOR]

In the present work, attempts have been made to control the yield strength anisotropy in an Al–Cu-Li alloy by implementing a novel processing route combining multi-axial forging (MAF) and rolling with an aim to weaken the texture. It has been observed that continuous destabilization of deformation texture during MAF results in weakening of texture. Further weakening of texture could be achieved upon post MAF cold cross rolling, which has been attributed to (i) the geometry induced shear in the roll gap, and (ii) the change in strain path during rolling. Such a weak texture is in contrast to strong Brass-type texture, generally observed in these alloys. Further annealing in the solution treatment regime led to even more weakening of texture. Uniaxial tensile tests along different directions of the as-processed sheets confirmed the weak dependency of yield strength on orientation of tensile axis. • Novel processing route of multiaxial forging and rolling is proposed for texture weakening of Al-Cu-Li alloys. • Texture weakening is due to continuous change in reference frame during multiaxial forging. • Further weakening of texture occurs due to geometric induced shear and change in strain path imposed during rolling. • Highly isotropic mechanical properties are obtained via the proposed processing method. [ABSTRACT FROM AUTHOR]

Nb-1wt.%Zr was subjected to severe plastic deformation at room temperature using multi-axial forging (MAF) in a closed channel die to an effective strain of 4.6. Separate such MAF samples of Nb–1Zr were subsequently annealed for 1 h at 450, 550, 600 and 700 °C to study the thermal stability of the microstructure after severe deformation. Electron backscatter diffraction measurements were used to characterize the microstructure in terms of grain size, local misorientations within grains and the fraction of recrystallization after annealing using the criteria of grain orientation spread. MAF increased the strength of Nb–1Zr to 540 MPa as compared to 120 MPa in the initial coarse grained condition. Subsequent annealing resulted in regions of recrystallized grains and an overall reduction in local misorientations. Annealing at 700 °C showed a bimodal grain size distribution with large recrystallized grains surrounded by deformed regions. The tensile strength reduced with increasing annealing temperature. The as-MAF and the 450, 550 and 600 °C annealed conditions showed low ductility (16%), whereas the 700 °C annealing condition showed a moderate ductility of 28% as compared to the coarse grained condition which showed a 44% ductility. It was estimated that the contribution of strength increase after MAF was more due to increase in dislocation density as compared to the reduction in grain size. [ABSTRACT FROM AUTHOR]

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 < 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. The effects of deformation processing path on the deformation mechanisms of a twinning‐induced plasticity (TWIP) steel at room temperature is investigate by Multi‐axial forging (MAF). The activation of deformation twinning along with substructure development even after 2 MAF passes leading to possessing continuous dynamic recrystallization beside twin fragmentation. The micro‐texture analysis is explored regarding deformation and grain refinement mechanisms. [ABSTRACT FROM AUTHOR]