Search

This paper presents a method for applying forging to high-density wood. A cylindrical container was formed using a closed die, and the appropriate conditions for temperature and punch length were evaluated. Ulin, which is a high-density wood, and Japanese cedar, which is a low-density wood and widely used in Japan, were used as test materials. The pressing directions were longitudinal and radial based on wood fiber orientation, and the shape and density of the resulting containers were evaluated. In the case of ulin, cracks decreased by increasing the temperature, while temperature had little effect on Japanese cedar. Containers without cracks were successfully formed by using a punch of appropriate length. The density of the containers was uniform in the punch length l = 20 and 40 mm in the L-directional pressing and l = 20 mm in the R-directional pressing when using ulin, with an average density of 1.34 g/cm3. This result indicates the forging ability of ulin is high compared to that of commonly used low-density woods. In summary, this paper investigated the appropriate parameters for forging with ulin. As a result, products of more uniform density than products made by cutting were obtained. [ABSTRACT FROM AUTHOR]

The evolution of eutectic Si morphology and microsegregation during homogenization heat treatment at 753K was examined for Al--Si--Cu--Mg--Ni alloy casting billets. Subsequently, casting billets homogenized at 753K for 0 s, 7.2 ks, and 28.8 ks were forged, and microstructures and mechanical properties at 473 and 573K were investigated for the forgings with different sizes of eutectic Si. Spheroidization of eutectic Si and elimination of microsegregation were achieved during the heating process of homogenization heat treatment. The spheroidized eutectic Si then coarsened with the homogenization heat treatment time. The interparticle spacing of the eutectic Si and constituent particles after the forging process increased with the coarsening of Si particles during homogenization heat treatment. In the tensile test at 473 K, the 0.2% proof stress, ultimate tensile strength (UTS), and elongation of the forgings were almost the same regardless of the homogenization heat treatment time, i.e., the size of eutectic Si. On the other hand, forgings made of a billet with a shorter homogenization heat treatment time showed more pronounced work-hardening behavior and higher 0.2% proof stress and UTS at 573 K. The increase in strength was explained by the enhancement of workhardening associated with the decrease in interparticle spacing, which depends on the Si particle size after homogenization heat treatment. [ABSTRACT FROM AUTHOR]

Copyright of Litua: Studies & Research / Litua: Studii și Cercetări is the property of Muzeul Judetean Gorj Alexandru Stefulescu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The evolution of eutectic Si morphology and microsegregation during homogenization heat treatment at 753K was examined for Al-Si-Cu-Mg-Ni alloy casting billets. Subsequently, casting billets homogenized at 753K for 0 s, 7.2 ks, and 28.8 ks were forged, and microstructures and mechanical properties at 473 and 573K were investigated for the forgings with different sizes of eutectic Si. Spheroidization of eutectic Si and elimination of microsegregation were achieved during the heating process of homogenization heat treatment. The spheroidized eutectic Si then coarsened with the homogenization heat treatment time. The interparticle spacing of the eutectic Si and constituent particles after the forging process increased with the coarsening of Si particles during homogenization heat treatment. In the tensile test at 473 K, the 0.2% proof stress, ultimate tensile strength (UTS), and elongation of the forgings were almost the same regardless of the homogenization heat treatment time, i.e., the size of eutectic Si. On the other hand, forgings made of a billet with a shorter homogenization heat treatment time showed more pronounced work-hardening behavior and higher 0.2% proof stress and UTS at 573 K. The increase in strength was explained by the enhancement of workhardening associated with the decrease in interparticle spacing, which depends on the Si particle size after homogenization heat treatment. [ABSTRACT FROM AUTHOR]

The article concerns the use of the results of numerical simulations, primarily for the detection of defects in forged products identified at various stages, along with the analysis of the geometry of forgings and the way in which the material flows in tools. The work presents the results of measurements and analyses using numerical modelling based on computational packages dedicated to forging processes such as: QForm, Forge, etc., which are equipped with special functions that significantly facilitate analyses by both technicians and designers. These functions include: contact of the deformed material with the tool, flow line distribution, "trap" or "fold" functions for detecting forging defects, as well as other technological parameters and physical sizes, which are crucial in the case of a comprehensive analysis of the industrial die forging process. The novelty of the work is the presentation of the possibility of simultaneously combining many different non-destructive techniques and methods, e.g. results of FE simulations with 3D reverse scanning, minimizing interference in the industrial process. The research carried out allows for the thorough and rapid analysis of the correctness of the deformation of the forging material for selected forging processes, along with the presentation of methods for their prevention and solving various technological and engineering problems, which is particularly important in terms of reliability and production efficiency. [ABSTRACT FROM AUTHOR]

The main objective of the present work is to produce AlxCoCrFeNiMo0.5 alloy through a wrought process. AlxCoCrFeNiMo0.5 high-entropy alloys with two different Al contents (x = 0.2 and 0.5) were prepared by vacuum arc melting followed by thermo-mechanical processing. Microstructural evolution was investigated after hot forging and subsequent homogenisation using XRD, SEM, and TEM. The final microstructure corresponding to Al0.2 and Al0.5 are BCT (sigma) in the FCC matrix and BCT (sigma) and ordered BCC together in the FCC matrix respectively. Room-temperature mechanical properties were investigated using uniaxial compression and hardness measurements. There is an apparent increase in strength and a decrease in ductility for the Al0.5 alloy. However, a higher ductility was observed in Al0.2 alloy with a compromised reduction in strength. [ABSTRACT FROM AUTHOR]

Work-related illnesses and the resulting employee absences can have a major impact on productivity and competitiveness, especially in small and medium-sized enterprises. Particularly in the forging industry, the manual handling of forged parts leads to high physical stress and thus to frequent illnesses of the musculoskeletal system, especially of the hand-arm system. One possibility to counteract this circumstance is the use of ergonomic forging tongs. In the study presented here, the influence of ergonomic forging tongs on the physical stress of forging employees was investigated by simulation and experiment and compared to conventional forging tongs. Within the simulation and the experimental investigation, forging parts and forging tongs were varied. In the simulation, an ergonomics assessment of the forging situation could be evaluated using the Ergonomic Assessment Worksheet. In the experimental study, gripping force measurements and calorie measurements were used to determine the impact of handling the forging tongs on the forging employees. The results show that the use of the new ergonomically optimized forging tongs can lead to a significant physical relief for the forging employees. The knowledge gained from the ergonomically developed concepts can also be transferred in other industries. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine if forged TiAl alloys are worth using for small parts such as jet engine turbine blades. As part of this goal, this study investigated ways to improve the impact resistance of forged TiAl alloys and compared them to cast TiAl alloys. The effects of additive elements and microstructure on the impact resistance of forged ternary TiAl alloys of 43.5 at. % Al were evaluated using the Charpy impact test on specimens heated to 500 °C prior to testing. The impact resistance of the forged alloys improved with the addition of Cr, V, and Mn and deteriorated with the addition of Nb. The impact resistance of the microstructure containing a β-phase, a common microstructure in forged TiAl alloys, was significantly lower. The fully lamellar structure obtained at the expense of forgeability showed much higher impact resistance than this. However, even the best impact resistance of the forged alloys was significantly inferior to that of cast ternary alloys of 46.5 at. % Al prepared with the same additive content. Combined with the high cost and low high-temperature strength of the forged TiAl alloys, it is concluded that it is pointless to use forged TiAl alloys for small parts that can be made via casting. [ABSTRACT FROM AUTHOR]

The “heat checking” phenomenon, which occurs due to thermal fatigue, is one of the dominant mechanisms in shortening the lifetime of dies which undergo sequential in-service high- and low-temperature operating cycles. This phenomenon results in the formation of a network of microcracks on the surface, which deepens with further repetition of thermal cycles. The service lifetime of dies made of hot work tool steel is characterized by successive changes from high to low temperatures. Hot deformation processes are subjected to working temperatures above 300 °C. In order to increase the die lifetime, many studies have been conducted to understand the mechanism of crack formation and find ways of prevention. However, there is no comprehensive study on the effect of the die production process, e.g., from the steelmaking to the die manufacturing step. In addition, it is important to understand the effect of service conditions on “heat checking” occurrence. In the present research, a short overview of this phenomenon has been provided including the definition, formation mechanisms and characteristics of “heat checking”. In addition, the influence of the steel characteristics such as surface engineering, heat treatment and service conditions on the phenomenon is investigated. As the simulation and theoretical aspects of “heat checking” are extensively investigated and summarized and the lack of knowledge is mostly in experimental parts, in order to fill the existing gap, this overview is preferentially focused on and summarizes experimental literature outputs rather than theoretical ones.

Aluminium finds wide application in mechanical engineering due to its low density and corrosion resistance. In this research, aluminium was subjected to two different metal forming technologies—cold forging (upsetting) and equal channel angular pressing (ECAP)—to obtain improvement in its exploitation properties. Parallel to changing mechanical properties by using these two processes, there was a change in the microstructure of the material. The resulting microstructures were examined using an optical microscope. A different treated aluminium was subjected to erosion wear in various time intervals. Wear testing was conducted for two different impingement angles causing abrasive wear and impact wear. The erosion mechanisms were examined by scanning electron microscopy. These results showed that there is no statistically significant difference in erosion wear for different states at the same impingement angle. However, the difference is noticeable at different wear angles. The significance of the difference in wear of the samples treated with the forging and ECAP techniques was validated by statistical analysis with tests of different sensitivities. The results of the t-test showed that ECAPed samples present a statistically significant difference in the loss of mass due to variations in erosion angle during the 30, 45, and 60 min wearing. A substantial difference in the change in sample mass is also visible for the forged state worn for 60 min.

The study discusses the issues of low durability of dies used in the first operation of producing a valve type forging from high nickel steel assigned for the application in motor truck engines. The analyzed process of manufacturing the exhaust valve forgings is realized in the coextrusion technology, followed by forging in closed dies. This process is difficult to master, mainly due to elevated adhesion of the charge material (high nickel steel – NCF3015) to the tool substrate as well as very high abrasive wear of the tool, most probably caused by the dissolution of hard carbide precipitates during the charge heating. A big temperature scatter of the charge during the heating and its short presence in the inductor prevents microstructure homogenization of the bearing roller and dissolution of hard precipitates. In effect, this causes an increase of the forging force and the pressures in the contact, which, in extreme cases, is the cause of the blocking of the forging already at the beginning of the process. In order to analyze this issue, complex investigations were conducted, which included: numerical modelling, dilatometric tests and hardness measurements. The microstructure examinations after the heating process pointed to lack of structure repeatability; the dilatometric tests determined the phase transformations, and the FEM results enabled an analysis of the process for different charge hardness values. On the basis of the conducted analyzes, it was found that the batch material heating process was not repeatable, because the collected samples showed a different amount of dissolved carbides in the microstructure, which translated into different hardnesses (from over 300 HV to 192 HV). Also, the results of numerical modeling showed that lower charge temperature translates into greater forces (by about 100 kN) and normal stresses (1000 MPa for the nominal process and 1500 MPa for a harder charge) and equivalent stresses in the tools (respectively: 1300 MPa and over 1800 MPa), as well as abrasive wear (3000 MPa mm; 4500 MPa mm). The obtained results determined the directions of further studies aiming at improvement of the production process and thus increase of tool durability.

Precise metal parts are manufactured using cold forged screw forming, but this method has drawbacks such as material damage and the possibility of imprecise parts. To ensure the accuracy and quality of parts, it is crucial to analyze and predict the forging force in this process. There are various methods to predict the forging force including laboratory testing, numerical simulation techniques, and simulation techniques. To provide forging information that cannot be measured by forging-forming machines, we simulated the nut-forming process based on actual manufacturing conditions using SolidWorks (v2020) with DEFORM-3D (v6.1). The results showed that the performance of the prediction of forging force specifications by the currently available nut-forming machines was improved by 8−20%. As the product becomes larger, the difference in forging force also increases proportionally. This research result, combined with appropriate experimental analysis, can be used as parameter controls for manufacturers in the future implementation of smart manufacturing. [ABSTRACT FROM AUTHOR]

The results of the study of the influence of multi-axial isothermal forging on the microstructure and martensitic transformation in a Ni58Mn18Ga24 alloy have been presented. Forging is performed in two stages: the first stage is forging at 700°C by four passes with true strain e ≈ 1.64; the second stage is forging at 500°C by one pass with e ≈ 0.24. The forging deformation results in the transformation of the original equiaxed-grain structure. No new grains are formed after the first stage of treatment. New recrystallized grains in a very negligible extent begin to be observed only after the second stage of deformation. Probably, at the first stage, the mechanism of fragmentation of the grain structure is not started due to an insufficient density of defects upon the deformation at 700°C. The characteristic temperatures of martensitic transformation are shifted after forging to the low temperature region. The anharmonic change in the sample length is observed in the region of martensitic transformation for the both treated states. In general, this indicates a low level of defect density and internal stresses in the sample. [ABSTRACT FROM AUTHOR]

This article discusses the results of our research into the effect of elongation on the welding of internal metallurgical discontinuities for two different geometrical shapes of a model feedstock of a selected magnesium alloy. Model discontinuities, specifically those of the metallurgical void type, were placed in various local zones of the modelled feedstock to check the influence of their location on their welding. The numerical modelling was carried out using the Forge®NxT2.1 application based on the finite element method. The results of the numerical tests were verified in laboratory conditions using the Gleeble simulator of metallurgical processes. Based on this research, it was found that the geometric shape of the feedstock material and the location of internal metallurgical discontinuities have a significant impact on the welding of discontinuities. The optimal values of the main process parameters of the elongation operation in flat dies were also determined for use in individual forging stages in order to eliminate internal metallurgical discontinuities. On the basis of the numerical studies carried out and their verification under laboratory conditions, it was concluded that a relative draft equal to 35% should be applied to weld the metallurgical discontinuities, which would result in a favorable hydrostatic pressure distribution within the discontinuities. [ABSTRACT FROM AUTHOR]

This paper focused on determining the increased tendency of cracking after the die forging process of high nickel and chromium steel. The increase in carbon content in austenitic nickel–chromium steel promoted the tendency of valve forgings to forging intergranular crack on the valve head. Attention was paid to issues related to the chemical composition of the material to be considered when hot forming nickel–chromium steel components. Optical and scanning electron microscopies were used to examine the microstructure and fracture features of the samples removed from a fractured valve head. The embrittlement was due to microcavity formation at grain boundaries. Creep theory at grain boundaries was used to explain crack formation. The tensile behavior was interpreted from the evolution of the microstructure during deformation and referred to intermediate brittleness to explain the effect of carbon. It was found that the increased carbon content of the nickel–chromium steel and the strong undercooling observed at the edges of the valve head are factors that promote a reduction in grain boundary cohesion and enhance intermediate temperature embrittlement. Finally, it was found that the formation of a heterogeneous structure manifested by the presence of grain boundary M23C6-type carbides in the austenitic matrix was most likely related to the occurring brittleness. [ABSTRACT FROM AUTHOR]

Background: Metal screws are commonly used for fracture fixations. However, the high modulus of elasticity relative to bones and releasing metallic ions by the metal screw needed a second surgery to remove the implant after the healing period. Furthermore, the removal of metal screws following the healing of the bone is a serious problem that can lead to refracture due to the presence of holes in the screw. Bioresorbable screws can overcome most of the problems associated with metallic screws which motivated research on manufacturing nonmetallic screws. Methods: In this study, three-layer poly L-lactic acid/bioactive glass composite screws were manufactured according to functionally graded material theory, by the forging process. All of the physical and chemical parameters in the manufacturing stages from making composite layers to the forging process were optimized to obtain suitable mechanical properties and durability off the screw in load-bearing positions. Results: The tri-layer composite screw with unidirectional, ±20° angled, and random fibers orientation from core to shell shows a flexural load of 661.5 ± 20.3 (N) with a decrease about 31% after 4-week degradation. Furthermore, its pull-out force was 1.8 ± 0.1 (N) which is considerably more than the degradable polymeric screws. Moreover, the integrity of the composite screws was maintained during the degradation process. Conclusions: By optimizing the manufacturing process and composition of the composite and crystallinity, mechanical properties (flexural, torsion, and pull-out) were improved and making it a perfect candidate for load-bearing applications in orthopedic implants. Improving the fiber/matrix interface through the use of a coupling agent was also considered to preserve the initial mechanical properties. The manufactured screw is sufficiently robust enough to replace metals for orthopedic load-bearing applications. [ABSTRACT FROM AUTHOR]

The casting of metal alloys followed by hot forging is a widely used manufacturing technology to produce a homogeneous microstructure. The combination of mechanical and thermal energy envisages the microstructural properties of metal alloys. In the present investigation, a metal alloy of composition 0.05C-1.52Cu-1.51Mn (in weight %) was cast in an induction furnace using a zirconia crucible. The melt pool was monitored using optical emission spectroscopy (OES) to maintain the desired composition. The as-cast block was then subjected to forging under a pneumatic hammer of 0.5 t capacity so that any casting defects were eliminated. The as-cast block was reheated to a temperature of 1050 °C and held at that temperature for 6 h to homogenize, followed by hammering with a 50% strain using a pneumatic hammer. The microhardness was calculated using a Vickers microhardness testing apparatus. The microstructure characterization of the processed alloy was carried out using an optical microscope, electron backscattered diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDXA), and a transmission electron microscope (TEM). The sample for optical microscopy was cut using a diamond cutter grinding machine and surface polishing was carried out using emery paper. Further, mechanical polishing was performed to prepare the samples for EBSD using a TEGRAPOL polishing machine. The EBSD apparatus was operated at a 20 kV accelerating voltage, 25 mm from the gun, and with a 60 µ aperture size. HKL Technology Channel 5 Software was used for the post-processing of EBSD maps. The procedure of standard polishing for OES and TEM sample preparation was followed. Recrystallization envisages equiaxed grain formation in hot forging; hence, the strain-free grains were observed in the strained matrix. The lower distribution of recrystallized grains indicated that the driving force for recrystallization was not abundant enough to generate a fully recrystallized microstructure. The fractional distribution of the misorientation angle between 15 and 60° confirms the formation of grain boundaries (having a misorientation angle greater than 15°) and dislocations/subgrain/substructures (having a misorientation angle less than 15°). The fraction of misorientation angle distribution was higher between the angles 0.5 and 6.5°; afterwards, it decreased for higher angles. The substructure was observed in the vicinity of grain boundaries. The softening process released certain strains, but still, the dislocation was observed to be deposited mostly in the vicinity of grain boundaries and at the grain interior. The fine precipitates of the microalloying element copper were observed in the range of size in nanometers. However, the densities of these precipitates were limited and most of these precipitates were deposited at the grain interior. The microhardness of 210.8 Hv and mean subgrain size of 1.61 µ were observed the enhanced microhardness was due to the limited recrystallized grains and accumulation of dislocations/subgrain/substructures. [ABSTRACT FROM AUTHOR]

Forgings are produced in several process steps, the so-called forging sequence. The design of efficient forging sequences is a very complex and iterative development process. In order to automate this process and to reduce the development time, a method is presented here, which automatically generates multi-stage forging sequences for different forging geometries on the basis of the component geometry (STL file). The method was developed for closed die forging. The individual modules of this forging sequence design method (FSD method) as well as the functioning of the algorithm for the generation of the intermediate forms are presented. The method is applied to different forgings with different geometrical characteristics. The generated forging sequences are checked with FE simulations for the quality criteria form filling and freedom from folds. The simulation results show that the developed FSD method provides good approximate solutions for an initial design of forging sequences for closed die forging in a short time. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study employs a high-fidelity numerical framework to determine the plastic material flow patterns and temperature distributions that lead to void formation during friction stir welding (FSW), and to relate the void morphologies to the underlying alloy material properties and process conditions. Three aluminum alloys, viz., 6061-T6, 7075-T6, and 5053-H18, were investigated under varying traverse speeds. The choice of aluminum alloys enables the investigation of a wide range of thermal and mechanical properties. The numerical simulations were validated using experimental observations of void morphologies in these three alloys. Temperatures, plastic strain rates, and material flow patterns are considered. The key results from this study are as follows: (1) the predicted stir zone and void morphology are in good agreement with the experimental observations, (2) the temperature and plastic strain rate maps in the steady-state process conditions show a strong dependency on the alloy type and traverse speeds, (3) the material velocity contours provide a good insight into the material flow in the stir zone for the FSW process conditions that result in voids as well as those that do not result in voids. The numerical model and the ensuing parametric studies presented in this study provide a framework for understanding material flow under different process conditions in aluminum alloys and potentially in other alloys. Furthermore, the utility of the numerical model for making quantitative predictions and investigating different process parameters to reduce void formation is demonstrated. [ABSTRACT FROM AUTHOR]

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 processingestructureeproperty correlation-ship. [ABSTRACT FROM AUTHOR]

The article presents the results of the study of the evolution of the deformed state of the workpieces, the energetic parameters of the process and the distribution of porosity over the volume of the forging at all stages of hot forging of porous powder forgings in an open die. Modeling of the process was carried out using the finite element method using the DEFORM 2D/3D software complex. As a result of the simulation, it was found that at the initial stage of the process, the blank is mainly compacted with minimal radial flow of the material. Noticeable flow of metal into the groove groove area begins only when the forging material reaches an average relative density exceeding 90%. A significantly different nature of the distribution of axial er and radial ez deformations over the volume of the forging was noted. A zone with increased levels of values of axial deformations is formed in the central layer of the forging, equidistant from the upper and lower surfaces of the die cavity, and the values of radial deformations decrease with distance from the zone bordering the free side surface of the workpiece in the radial (to-center) direction. The minimum values of ez and er appear in the upper and lower angular stagnant zones of the forging. It is shown that the graph of the dependence of the deformation force on the displacement of the punch is marked by the presence of at least three characteristic sections due to the relationship between the processes of compaction and forging shape change at each stage of the process. [ABSTRACT FROM AUTHOR]

In the present work, the relationship between deformation, microstructure and mechanical properties of the Sr-modified 4032-type eutectic aluminum alloy was studied. The alloy was prepared from recycled materials, mainly from maritime and automotive 356 alloy scrap samples. Solubilizing heat treatment was carried out at a temperature of 450 °C with a holding time of 8 h. Finally, different samples were subjected to rolling and forging processes at a temperature of 450 °C, thus achieving a reduction of 25% of the original thickness. As expected, the microstructure and properties changed significantly due to the deformation processes, where an important factor was the change in the morphology of eutectic silicon, not only produced by the application of deformation, but also on the effect of adding strontium as a modifying agent. The samples were characterized by optical microscopy and scanning electron microscopy, where it was possible to observe not only the effect of strontium on the morphology of eutectic silicon but also the effect of the heat treatment performed. The tensile tests showed that there was indeed a notable increase in the ultimate tensile stress, yield strength, and resistance to fracture, while initial hardness also considerably increased. Finally, the fracture analysis showed that, after thermal treatment and deformation, all the samples analyzed presented a fracture within the ductile regime. It was shown that the combination of deformation and the addition of strontium led to improved globulization of the eutectic silicon. [ABSTRACT FROM AUTHOR]

The specific features of a copper–nickel MN45-VP constantan alloy of vacuum melting are taken into account to reveal the possible causes of the appearance of characteristic hillocks on metallographic sections of its rods as a kind of surface whisker effect. The formation of hillocks is shown to be a consequence of diffusion processes induced by a high chemical heterogeneity of the material. This heterogeneity is found to be related to the absence of special electromagnetic devices in an induction melting furnace for mixing the melt, the components of which are separated in magnetic susceptibility. In other words, the time of holding the melt during cooling-down in the course of degassing is too short. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metal forming uses plastic deformation to change the shape of the workpiece. Deformation or change in shape results from the use of a tool which is usually called a die. The die provides stresses that exceed the yield strength of the material (plastic). The forging process is one of several types of metal forming. A power hammer machine is a machine used for the formation of a product in the manufacturing process, namely with a system of continuous forging/pressure on the specimen so that the deformed specimen becomes denser and stronger according to the desired shape. The forging process is superior to other processes such as casting and machining. The effectiveness of the forging process is characterized by low costs, high productivity, and high product quality. The cold forging process needs to be improved to reduce the occurrence of fine cracks and defects. The main factor is the quality of forging results by planning the design and production of the right die, improving product quality, and reducing the number of defective products to encourage industrial competitiveness. The method in this research is the process of making the design and calculation of the main components and making the power hammer machine. The results of the design and manufacture of the power hammer machine obtained that the impact force from the design was 58.3 Kg, the rotation of the drive shaft to drive the hammer was 206.5 Rpm, the diameter of the driving shaft was 12.36 mm with the one made of 16 mm, the torque on the driving motor was 77.9 Nm, the minimum power designed is 2.2 hp with a rotation of 2800 Rpm, and is selected for the manufacture of 3 Hp, the electrical system is on / off using a throttle stomp.

The forming limit of AZ31 alloy, a representative Mg-Al-Zn-based wrought alloy, and the effect of severe plastic deformation (SPD) by examining the microstructure change caused by dynamic recrystallization led by high temperature and high dislocation density at 300℃ using a biaxial alternate forging (BAF) were investigated in this study. As a result of BAF test for AZ31 Mg alloy, significant cracks on the ends of workpieces occurred after 7 passes. The microstructure of as-extruded specimen showed the non-uniform distribution of the relatively coarse grains and the fine grains considered to be sub-grains. However, as the number of passes increases, the area of coarse grains gradually disappeared and the fine grains became more dominant in the microstructures. The result of tensile test for workpieces with each forging pass showed an increase in strength depending on pass number was shown with a slight increase of elongation. The Electron Backscatter Diffraction (EBSD) results exhibited that, the microstructure showed the presence of coarse grains and twins after only 1 pass, while the grains appeared to be significantly refined and uniformly distributed after 3 pass, at which the strength and elongation began to increase, simultaneously.

This paper presents the environmental impacts of reciprocating engine component (REC) made of cast iron and low-alloy steel in Finland using life cycle assessment (LCA). The study uses primary data provided by a machining shop in Finland covering cradle-to-gate with a functional unit of 1 tonne of REC. The assessment was carried out using CML-baseline, resulting in eleven impact categories emphasising global warming potential (GWP). The results show that the upstream process, including forging and foundry, to manufacture the material inputs contributes the highest among all impact categories, making up about 52–97% of the total impacts. For GWP, the total emission to manufacture 1 tonne REC is about 2926 kg CO2 eq. Sensitivity analysis indicates that material inputs of cast iron and low-alloy steel are the most critical parameters making process efficiency and technological advance prominent. This study highlights the importance of selecting suppliers, energy sources, and transportation modes. [ABSTRACT FROM AUTHOR]

This paper presents results on the microstructure and mechanical properties of a new low-cost titanium alloy Ti-5Al-1.5Mo-1.8Fe after different forging processes. The β phase transformation temperature of this alloy was 950 °C. In this study, the forging temperatures were designed at 920 °C and 980 °C, and the deformation degree ranged from 20% to 60%, with an interval of 20%. This study investigated the impact of the equiaxed α phase and shape of the lamellar microstructure on the tensile characteristics and fracture toughness of an alloy. The research employed a microstructure analysis and static tensile testing to evaluate the effect of forging temperatures and degree of deformation on the microstructure features. The findings revealed that forging temperatures could modify the microstructure characteristics, and the degree of deformation also affected this microstructure. This study demonstrates that a bimodal structure with an equiaxed α phase can be utilized to balance high strength and high ductility, resulting in better overall mechanical properties. [ABSTRACT FROM AUTHOR]

This investigation reports the influence of vol.% and size (micrometric/nanometric) of the reinforcement particles on machinability of near-full-density (> 99% relative density) powder-forged Al-7075/Y2O3 composites. The composites were processed with 0.1-3. vol% nanometric and 1-10 vol.% micrometric reinforcement and studied in artificially aged (T6) and solutionized conditions. Drilling was performed without applying cutting fluid at 140 rpm rotational speed and 0.12 mm/rev feed rate to produce through holes. Cutting force components (Ft and Fc) and machined surface roughness (Ra) were considered as machinability criteria. The results showed that the reinforcements influence Ft and Fc in both conditions correspondingly as they cause structural alterations and affect composites' hardness. Nevertheless, the reinforcements' effects in T6 were not as prominent as in solutionized condition. In the former condition, the hardness of the alloy matrix due to the formation of precipitates overrides the hardness due to structural alterations caused by reinforcements. Pull-out of secondary reinforcement particles was observed while machining. Besides the composites' hardness, abrasion of the pulled-out reinforcement particles and stuck-up debris of the broken chips on the freshly machined surface governs its roughness. Only a few earlier studies have opted for Y2O3 reinforcement and processed Al-7075/Y2O3 composites by powder forging. Further, machining of Al-7075/Y2O3 composites in solutionized and T6 conditions has been scarcely investigated, and their machinability has been hardly ever analyzed with respect to reinforcement parameters, size, and vol.%. [ABSTRACT FROM AUTHOR]

The article presents the results of numerical analysis of the new forging process of the connector forging from cast preform on hydraulic press. The high strength ZK60 alloy (belonging to the Mg-Zn-Zr group of Mg alloys) was selected to numerical tests. Currently, this part in the industry is produced by multi-stage forging consisting of operations: bending, preforming, and finishing. The use of the cast preform would enable forging this component in one operation. However, obtaining specific mechanical properties requires inducing a certain level of strain within the forged part. Therefore, the design of the preform, its shape and volume, is of paramount importance. In the work presented in this article, preforms of different shapes were designed and assessed using Finite Element Method (FEM) analysis. [ABSTRACT FROM AUTHOR]

As a field of forensic science, graphoscopy studies the legalities of writing and develops methods for examining and identifying the person who forged a document or signature. The identification is made on the basis of an expertise carried out by an expert in the field, ordered by the competent bodies. [ABSTRACT FROM AUTHOR]

The objective of this study was to enhance the properties of the inner surface of a rifle barrel. The substrate utilized in this investigation was produced through the cold forging technique using 42CrMo4 material, measuring 260 mm in length and 5.56 mm in diameter. Electrolytic hard chromium plating was employed to create a durable metal layer on the inner surface of the substrate. A peristaltic pump was utilized to eliminate gases, such as hydrogen and oxygen, which evolved at the cathode and anode during the process. An anode material comprising a steel rod coated with a 93% Pb-7% Sn alloy, possessing a diameter of 2.35 mm, was employed in the coating experiments. Vickers hardness testing was performed to measure the hardness of both the substrate and the coating layer. The coating thickness ranged approximately between 23 µm to 30 µm. Hardness analysis conducted at various points indicated a proportional decline in coating microhardness with increasing coating thickness. Following the electrolytic hard chrome plating process, the inner surface hardness of the barrel reached approximately 1143 HV0.025. [ABSTRACT FROM AUTHOR]

Wear and fracture of steel dies employed in hot forging were evaluated through metallographic study with the aim of qualifying a Finite Element Simulation of the productive process. Apart from providing useful insights into the causes of die damaging, the simulation was exploited in a Design of Experiments to prevent fracture and to counter different mechanisms of wear. The objective is the optimization of die life acting only on process parameters that are directly adjustable in the actual industrial process. In the examination of stress distribution on the dies and the estimation of die wear, the complete forging cycle has been taken into consideration. Despite the considerable variability of the process, the study demonstrates that it is possible to prevent fracture insurgence and to increase the life expectancy of the die by a careful tuning of standard process parameters. Possible stakeholders of the study are not only process designers but also production managers, as most process parameters are modifiable during production. [ABSTRACT FROM AUTHOR]

Brass materials are categorized in the copper alloys sub-groups with prevailing Zinc element. These materials are utilized from drinking water systems to automotive in a wide range of industrial applications due to superior properties such as strength, formability and corrosion resistance. This study aims to characterize and analyze smart and popular conducted manufacturing processes influences on the mechanical and microstructural properties of eco-friendly brass alloy. In this regard, microstructural, hardness, tensile and impact charpy tests have been carried out on extruded, extruded+annealing, forged and forged+annealing eco-brass CuZn40Pb2, CuZn38AS, CuZn21Si3P specimens. The experimental results have demonstrated that the manufacturing process type extremely influences the materials mechanical and microstructural properties. [ABSTRACT FROM AUTHOR]

In our previous works, the effects of forging and heat treatment variables on microstructure evolution and mechanical properties have been studied for an ingot-metallurgy Re-bearing nickel base superalloy. To overcome the issues associated with the production of large-scale ingots and fine-grained workpieces, in the present work, the effect of hot forging and heat treatment variables was studied in a Re-bearing nickel base superalloy prepared via powder metallurgy. The purpose of the study was to reach the properly balanced mechanical properties for the potential use of the superalloy as a disc material. The initial as-HIPed workpieces were subjected to different hot forging and post-forging heat treatment or only to heat treatment (no forging). For the processed workpieces, the recrystallization behavior, size, morphology and volume fraction of γ′ precipitates were evaluated by scanning electron microscopy followed by a study of mechanical properties. The most properly balanced mechanical properties (strength, ductility, creep resistance and creep rupture lifetime) were reached for the γ grain size of dγ ≈ 13.6 µm. A finer and coarser γ grain size (down to dγ ≈ 2.6 and up to dγ ≈ 37.5 µm) even when superimposed with a higher volume fraction of dispersed secondary γ′ precipitates (in the case of dγ = 27–37.5 µm) was associated with worse mechanical properties. [ABSTRACT FROM AUTHOR]