Alloy Forgings Research Articles

A New Dynamic Recrystallization Kinetics Model of Cast-Homogenized Magnesium Alloys

Dynamic recrystallization always occurs during hot forming of magnesium alloys and largely controls their microstructure evolution. In this study, we developed a new dynamic recrystallization kinetics model with one undetermined parameter based on isothermal compression tests of a cast-homogenized Mg-8Gd-3Y alloy (GW83) at temperatures ranging from 300 °C to 450 °C and strain rates from 0.001 to 0.1 s−1, and measured its dynamic recrystallization volume fractions. The undetermined parameter could be determined by parameter regression. The adaptability of the new model was further examined by comparison with the published data of isothermal compression experiments of AZ31B and ZK60 alloys. The predicted results were well consistent with the experimental results. By integrating the new model with finite element software, we investigated the dynamic recrystallization kinetics of upsetting and plane strain forging of GW83 alloy. The predicted distributions of the dynamic recrystallization volume fraction agreed very well with the experimental values under four different sets of isothermal deformation conditions. These results indicated that the new dynamic recrystallization kinetics model affords highly accurate predictions of the kinetics of cast-homogenized magnesium alloys.

Measuring internal residual stress in Al-Cu alloy forgings by crack compliance method with optimized parameters

Measuring the internal stress of Al alloy forgings accurately is critical for controlling the deformation during the subsequent machine process. In this work, the crack compliance method was used to calculate the internal residual stress of Al-Cu high strength alloys, and the effect of various model parameters of crack compliance method on the calculated precision was studied by combining the numerical simulation and experimental method. The results show that the precision first increased and then decreased with increasing the crack range. The decreased precision when using a high crack range was due to the strain fluctuation during the machining process, and the optimized crack range was 71% of the thickness of forgings. Low orders of Legendre polynomial can result in residual stress curve more smooth, while high orders led to the occurrence of distortion. The Tikhonov regularization method effectively suppressed the distortion of residual stress caused by the fluctuation of strain data, which significantly improved the precision. In addition, the crack compliance method with optimized parameters was used to measure the residual stress of Al-Cu alloy with different quenching methods. The calculated results demonstrated that the distribution of residual stress was obtained accurately.

Effect of Secondary Aging Process on the Structure and Properties of 7050 Aluminum Alloy Forging

The effect of the second-stage aging process on the tensile properties, fracture toughness and electrical conductivity of 7050 aluminum alloy die forgings was studied, and the mechanism of strengthening and toughening was analyzed by transmission electron microscope and scanning electron microscope. The results show that with the extension of the second-stage aging time, the morphology of the precipitation phase remains unchanged, but the average radius of the precipitation phase and the distance between each other gradually increase. The fracture modes at this aging temperature are mixed fracture mechanisms of dimple fracture and intergranular fracture, and the number of dimple fractures increases with time. With the extension of the second-stage aging time, the strength of the alloy decreases, and the fracture toughness and stress corrosion resistance increase. The alloys heat-treated at 120°C×6 h +177°C×6~8 h two-stage aging process have excellent comprehensive properties.

Typical Microstructural Characteristics of Ti–5Al–5Mo–5V–3Cr–1Fe Metastable β Ti Alloy Forged in α + β Region

In this study, typical microstructural characteristics of a metastable β Ti alloy (Ti–5Al–5Mo–5V–3Cr–1Fe) forged in a dual-phase region (strain of 54% at 820 °C) were investigated in detail by the combined use of X-ray diffraction, energy dispersive spectroscopy, electron channeling contrast imaging and electron backscatter diffraction techniques. Results show that the microstructure of the forged alloy is composed of bulk α grains, α plates and β matrix. The bulk α grains correspond to retained primary α phase (αp, average grain size ~ 2.4 μm), while the α plates are secondary α phase (αs, width ~ 70 nm) precipitated from the β matrix during air cooling. During forging, the β matrix experiences dynamic recovery with many subgrains and significant orientation gradients formed. Analyses of the orientation relationship between the α and β phases show that the Burgers orientation relationship is not maintained between some αp and β phases, which should be related to thermal deformation-induced changes of their orientations. In contrast, all of the αs plates are found to maintain well the Burgers orientation relationship with the β phase.

Peculiarities of Microstructure Evolution and Property Changes of Titanium Alloys In Situ during Electric Forging

Abstract The experimental studies of the parameters of hot electric forging were carried out on industrial heat resistance (α + β), (near-α), and (α″ + β) titanium alloys. It was established that simultaneous fast Joule heating with a high-density electric current and an initial temperature of hot intense plastic deformation are important parameters for the electric forging of heat resistance titanium alloys. The heating rate dependence on electric current density and thermophysical properties of metal, as well as deformation temperature dependence on axial compression stress and mechanical strength of heated metal under compression as the main parameters of electric forging, were chosen. To calculate the processing parameters, we investigated the evolution of the thermophysical properties and mechanical strength of selected titanium alloys at a heating rate of 50°C·s−1 at a temperature up to 1,200°C. Microstructural evolution and the phase transformation temperature were determined using optical and scanning electron microscopes. The results show that the grinding efficiency of the coarse-grained microstructure depends on the increase of the heating rate, and the formation of uniaxial ultrafine alpha-phase grains depends on an increase of the compressive stress or decrease in the deformation temperature. It can be argued that the compressor blades made of titanium alloys for aircraft turbojet engines had increased ductility, stability, and high-cyclic fatigue strength, as well as increased operating life at ambient temperatures. The results can be used to model and calculate the rational parameters of electric forging to improve the operational properties of the final products.

Phased array ultrasonic imaging using angle beam virtual source full matrix capture-total focusing method

Full matrix capture coupled with total focusing method (FMC-TFM) is one of the most advanced and popular phased array ultrasonic techniques used to achieve simultaneous focusing at all depths in a specimen. In case of conventional FMC-TFM technique, a single element is used for transmission that limits the transmitted energy. This leads to reduced sensitivity at larger depths particularly in attenuating materials such as austenitic alloys. An Angle Beam Virtual Source FMC (ABVSFMC) method is proposed in the present paper to enhance the sensitivity by increasing the transmitted energy with specific directivity. The methodology utilizes apertures of a few elements to obtain a diverging beam by focusing very near to the top surface (virtual source). Further, as a group of elements is used in transmission, a divergent beam with specific directivity can be achieved without using a wedge. In reception, all the available channels are used and an algorithm similar to the Total Focusing Method (TFM) is used to reconstruct the image. The methodology is demonstrated by imaging the tip diffracted signals obtained from slot type planar defects at various depths in the range of 25–175 mm in a 200 mm thick nickel base alloy forging.

Failure analysis of inlet guide vane (IGV) actuator and bellcrank assembly used on J85 turbojet engines

This study presents the metallurgical analysis results of fracture failure occurred on the arm of Inlet Guide Vane (IGV) actuator and bellcrank assembly that used on J85-GE-5 turbojet engine. The broken arm material is determined to be AMS4134 Aluminum Alloy Forging. Material composition of Aluminum alloy consists of 93.35%-Al, 4.5%-Cu, 0.85%-Si, 0.8%-Mn and 0.5%-Mg. The average hardness value of the material is measured to be 75 HRB. The metallurgical analysis results indicate that the corrosion assisted fatigue under the influence of repeated loading and corrosion started the micro fractures and cracks on the IGV actuator and bellcrank assembly arm surface, then residual cross-section surface were completely sheared off because the residual cross-section surface did not endure the over load effects overcoming on it. The fatigue area of the arm covers approximately 1/3 of the total cross-sectional area.

Casting of High Aluminum Content AM Series Magnesium Alloys by Using a Horizontal Twin Roll Caster

In this paper, twin roll casting of magnesium alloys with high aluminum content such as, Mg-11 mass%Al-0.2 mass%Mn, Mg-12 mass%Al-0.2 mass%Mn, Mg-13 mass%Al-0.2 mass% have been performed for the purpose of use as an original material for hot forging. Also the mechanical properties of the cast materials were examined. A 10 miri-meters thick strip was cast by the use of a horizontal twin roll caster. The microscopic observation was conducted to investigate into the precipitation of the metal compounds such as Mg17Al12, and the Vickers hardness of the cast strips test were performed. From the result of the roll casting experiments, a 10 mm thick strip was continuously cast at a roll speed of 3.1 m/min. The average grain size of the casting strips was about 46 micron meters. When the aluminum content was 13%, the hardness of the twin roll cast (TRC) strips became 1.7 times higher than that of extruded AZ 31. Also, a uniaxial compression test at elevated temperature was conducted to obtain a true strain-true stress curve for examining possibility of direct hot forging (DHF) of TRC magnesium alloys with high aluminum content.

Use of Multi-Modal Synchrotron Analytical Techniques to Understand Anomalous Localized and General Corrosion Behavior of Additively Manufactured 316L Stainless Steel

Additive manufacturing (AM) of alloys such as stainless steels has the potential to be a disruptive technology for design of complex structures which eliminates the potentially damaging effects of mechanical failure and localized corrosion associated with interfaces between separate parts (which can now be printed as part of a single assembly). In addition, increasingly complex geometries can be manufactured with nearly as much ease as simple ones, and new mechanisms for optimization and generative design can allow manufacturers to achieve significant material and weight savings. However, challenges remain, in particular due to the potential for material variabilities both between parts made with the same nominal build parameters and even within a single build, as the consistency in properties inherent in the commercial-scale forging of alloys to be machined into components is exchanged for the considerable advantages of on-site, distributed custom parts production. Our studies and related work by other groups indicates that this is clearly true in the case of corrosion susceptibility in AM alloys. By studying the relationship between build parameters and electrochemical properties, we propose that it will be possible to tailor alloys for enhanced corrosion properties.AM processes produce materials with hierarchical microstructures containing fusion boundaries at the macroscale, irregular grains and grain boundaries at the microscale, and subgrain dislocation structures at the nanoscale. In laser powder bed fusion (LPBF) formed 316L stainless steel structures, corrosion performance has been discussed in the context of chemical heterogeneities formed in the presence of these hierarchical microstructures. However, the large variability in reported measurements underscores the need for statistically significant microstructural data, which is often difficult to access via electron microscopy alone. In this presentation, we explore multi-modal synchrotron X-ray techniques for quantifying hierarchical microstructures and their connection to the underlying chemical distribution in 316L stainless steel. Our results show that the dislocation density depends on the printing conditions with implications for the chemical distribution at the nanoscale, which in turn may play a key role in inconsistent corrosion behavior.LPDF 316L samples formed at varying speeds using pulsed and continuous laser deposition are compared via cyclic polarization in 3.5% NaCl and 0.1M HCl solutions, as well as using standard methods for characterizing sensitization. Surface corrosion layers are characterized using laboratory-based X-ray photoelectron spectroscopy to determine the impact on passivity of the aforementioned microsegregation associated with process-induced microstructures. Corrosion rates and pit densities are then discussed to build a connection between printing conditions and corrosion performance vis-à-vis microstructural and chemical information from synchrotron measurements performed at Brookhaven National Laboratory (BNL), including high energy X-ray diffraction using the X-ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source-II (NSLS-II) which provided data on minor precipitate population(s), atomic structure and dislocation microstructures critical to corrosion behavior. In addition, heterogeneities in elemental composition data is provided by 2D X-ray fluorescence (XRF) and 2D X-ray Absorption Spectroscopy (XAS) nanometer resolution-mapping obtained at the Hard X-ray Nanoprobe (HXN) beamline at the NSLS-II and correlated with process-induced hierarchal structures via use of the microscopy facilities at the Center for Functional Nanomaterials (CFN).By employing a combination of multi-modal synchrotron characterization techniques, electron microscopy, and baseline testing protocol combined with electrochemical polarization experiments, we are able to study the the role of microstructure across multiple length scales on electrochemical properties and corrosion performance. Understanding the impact of microstructure and chemical heterogeneities on the susceptibility to pitting and intergranular attack will enable microstructurally-informed process optimization and materials design for enhancing the corrosion resistance of LPBF 316L stainless steel, with implications for AM and subsequent durability of alloys in general.

Fatigue Crack Growth Behavior of TA29 Titanium Alloy at Different Temperatures

TA29 titanium alloy forging was heated by duplex annealing. The fatigue crack growth behaviour of the alloy at room temperature, 400 °C, 500 °C and 600 °C was studied. The relationship between the fatigue crack growth rate (Da/dN) and the stress intensity factor amplitude (△K) of TA29 alloy at different temperatures was revealed by Paris formula. The fatigue fracture morphology of fatigue crack growth specimens was analysed by scanning electron microscopy (SEM). The results showed that the TA29 titanium exhibited good crack growth resistance at room temperature. With the increase of test temperature, the C value of the Paris formula increased, the m value decreased, and the fatigue crack growth rate increased. From the fatigue fracture morphology of the specimens, it was found that the fractures of fatigue crack growth specimens at different temperatures exhibited typical pre-splitting zone, steady-state expansion zone and rapid expansion zone. As the temperature increased, the range of the pre-cracking zone was larger, the range of the steady-state extension zone and the rapid expansion zone were smaller. At room temperature, there was no obvious fatigue strips in the steady-state expansion zone, and the transient fracture zone exhibited the characteristics of cleavage fracture, while the steady-state expansion zone at high temperature showed obvious fatigue strips and secondary cracks, and the transient fracture zone was a typical ductile fracture mechanism.

Investigation on Compressive Formability and Microstructure Evolution of 6082-T6 Aluminum Alloy

The 6xxx aluminum alloy is the first choice for automotive lightweight forgings due to its excellent performance, high strength and low weight. The production time of current aluminum alloy forging generally exceeds 10 h. To reduce the production time of traditional aluminum alloy forgings, 6082-T6 aluminum alloy is used in the forming process. The effects of different heating temperatures (200 °C, 300 °C, and 400 °C) and deformation degrees (30%, 50%, and 70%) on the deformability and properties of 6082-T6 billets have been investigated. The results show that when the heating temperature is higher than 300 °C, the compressive deformation resistance obviously decreases with increasing strength. With compression at 200 °C and 70% deformation with short heating time, the strength of the sample is close to the T6 (solution treatment and artificial aging) state. A large number of dislocations and subgrains were introduced due to the compression deformation, and their amounts decreased as the heating temperature increased. The size of the precipitated phase β′′ slightly grows under a heating temperature of 200 °C. However, when the heating temperature is higher than 300 °C, the precipitated phase gradually changes from β′′, which is optimal for the strengthening effect, to β′ and β, which offer weaker strengthening. Therefore, under a lower heating temperature of 200 °C for 5 min, a large number of dislocations are introduced with the β′′ precipitated phase, leading to higher strength with less heat treatment time.

Dynamic mechanical response and weldability of high strength 7A62 aluminum alloy

The 7A62 as one kind of Al-Zn-Mg alloys is the highest strength weldable aluminum alloy currently. Plates and forgings of 7A62 alloy have been widely used in the defense system and main bearing parts of special vehicles. The microstructure, dynamic mechanical response and weldability of 7A62 aluminum alloy were investigated by OM, TEM, SHTB, DSC, microhardness and other tests. The morphology and mechanical test results showed that the 7A62 aluminum alloy strengthened by trans-scale precipitates had high strength, high hardness and good plastic toughness. The mechanical responses of the 7A62 aluminum alloy were found to be strain-rate sensitive and the dynamic response behavior was significantly higher than that of the 7A52 aluminum alloy through the SHTB test. In addition, for the as-welded 7A62 the tensile strength reached a scope of 260 MPa-305 MPa, which is considerably higher than the tensile properties reported when using ER5356. Because the weld of 7A62 alloy was free of macroscopic imperfections. The grains were highly equiaxed and homogeneous throughout the melting zone, showing smooth grain boundaries. Compared with 7A52, the lower melting point, low thermal enthalpy and low specific heat capacity of 7A62 alloy are more conducive to weld performed.

Use of computer simulation for modernization technology of aluminum alloys hot die forging

A methodology for the modernization of technological processes for the hot forging of aluminum alloy forgings based on computer simulation has been developed. The modernization procedure is outlined, including the analysis of an analogous technological process, the development of a virtual technological process structure, the creation of forging and die models in the SolidWorks program, the formulation of a computer simulation problem, the input of simulation parameters, the launch and analysis of a computer technology model, and the development of recommendations for modernizing an existing process with subsequent pilot testing of technology. An example of the methodology was the die forging technology “Rack” made of 5083 alloy, which is a single-plane complex-shaped panel with stiffeners. The analysis of the technology-analogue made it possible to formulate the problem of finding the possibility of reducing operations. Temperature, speed, and power deformation modes were introduced, which were a deformation rate of 0.3 mm/s, billet-heating temperature 450 °C, and the temperature of a die 400 °C. The output was a database of the process. At the end of the virtual experiment, the technology was tested on laboratory equipment, and a comparative analysis of the two technologies was carried out, which presented the advantages of the proposed isothermal die forging technology and developed recommendations for updating the existing technology. The transition to isothermal die forging will reduce the number of passes from three to one. All this will lead to an increase in metal utilization rate from 0.44 to 0.77.

Mg-Alloys for Forging Applications-A Review.

Interest in magnesium alloys and their applications has risen in recent years. This trend is mainly evident in casting applications, but wrought alloys are also increasingly coming into focus. Among the most common forming processes, forging is a promising candidate for the industrial production of magnesium wrought products. This review is intended to give a general introduction into the forging of magnesium alloys and to help in the practical realization of forged products. The basics of magnesium forging practice are described and possible problems as well as material properties are discussed. Several alloy systems containing aluminum, zinc or rare earth elements as well as biodegradable alloys are evaluated. Overall, the focus of the review is on the process control and processing parameters, from stock material to finished parts. A discussion of the mechanical properties is included. These data have been comprehensively reviewed and are listed for a variety of magnesium forging alloys.

The analysis of flow behavior of Ti-6Al-2Sn-4Zr-6Mo alloy based on the processing maps

The paper presents the analysis of hot deformation behavior of Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) alloy using the theory of dynamic material modeling (DMM) based on hot compression tests performed to a total true strain of 1 at the strain rates from 0.01 to 100 s−1 and at the temperatures within the range between 800 and 1100 °C. The processing maps according to the Prasad’s criterion were developed. The analysis of the processing maps allowed for the placement of domains describing the areas of potentially favorable combinations of hot deformation parameters. The microstructure observations of the investigated alloy specimens after hot deformation in stability and instability areas were conducted. The optimal processing parameters for numerical modeling of Ti-6246 alloy forging were selected based on processing maps. After complex analysis of the obtained results, microstructural observations and numerical modeling of forging of selected part, the forging tests of Ti-6246 alloy were realized. The obtained product quality assessment was carried out by computed tomography non-destructive testing.

Prediction of Mechanical Properties of Ti-6Al-4V Forgings Based on Simulation of Microstructure Evolution

Titanium alloys are widely used in the aerospace industry as a structural material. Since this application is critical, the titanium alloys must have high mechanical properties both at room and at elevated temperatures. The thermomechanical processing of titanium alloys during forging determines the microstructure of the manufactured parts to a large extend. The final mechanical properties are attained by the subsequent heat treatment. Hardening heat treatment, such as solid solution treatment and aging, improves both the strength and ductility of the material. Simulation of metal forming processes with the evolution of the microstructure and prediction of the final mechanical properties are extremely important and allow to effectively develop a technological process for the production of high-quality parts. The most widely used titanium alloy is Ti-6Al-4V, which combines high mechanical properties and satisfactory processability and can be used at temperatures up to 350 °C. In this work samples of Ti-6Al-4V alloy having a lamellar structure with different morphology and a duplex structure with different globular alpha-phase fractions and average grain sizes have been studied. The mechanical properties at the room temperature were determined using compression tests. These experimental data were used to develop a model that allows for predicting the mechanical properties of Ti-6Al-4V alloy forgings after the final heat treatment. The model has been tested by forging a turbine blade using the QForm software.

Cold bulging process for aluminium alloy ring with irregular section

Large size aluminium alloy seamless ring with irregular section is usually obtained by hot ring rolling process. Because of residual stress, the ring generally experiences much deflection during subsequent aging and machining. To control this deflection and strengthen the aluminium alloy ring, cold bulging process has to be applied to the ring to homogenize residual stress before aging and machining, and the uniformity of cold deformation is the key problem. The cold bulging process was designed for the forging of the casing ring of aluminium alloy with 5-meter special-shaped section. On this basis, the stress analysis of the cold bulging process was made and the process was engineered. By using Deform-3D to conduct finite element analysis on the ring cold bulging process and stress analysis on different positions of the ring, the deformation characteristics of the ring under the cold bulging process were obtained. The uniformity of the deformation of the ring was achieved by means of the rotation of the disc die when the ring was bulging. The bulging process in the engineering scheme greatly improved the uniformity of the strain in each region of the ring, which provided a reliable theoretical analysis and engineering scheme for the cold bulging process of the ring forgings of aluminium alloy casing with irregular section.

Effects of thermomechanical treatment on grain refinement, second-phase particle dissolution, and mechanical properties of 2219 Al alloy

Abstract An improved thermomechanical treatment, which included 50% hot deformation at 440°C, 10% cold predeformation at 25°C, and a subsequent heat treatment (solution, 2.5% cold deformation and aging treatment), was performed on 2219 Al alloy forgings. For comparison, a 2219 Al alloy forging was also manufactured using the conventional process, which involved 50% hot deformation at 440°C and a subsequent heat treatment. The evolution of the microstructures of the forgings during the treatments and their final mechanical properties were evaluated. A large number of Al2Cu particles were formed during the hot-deformation process. Further, tangled dislocation structures were formed around these particles after 10% cold deformation in the forging manufactured by the improved process, resulting in a significant grain refinement during the solution treatment because of particle stimulated nucleation as well as a weakened texture. In addition, more coarse Al2Cu particles dissolved into the Al matrix during the solution treatment in the case of the forging subjected to the improved treatment, because the tangled dislocation structures promoted the dissolution of these particles, thus increasing the density of the precipitates after T8-aging. The forging manufactured by the improved treatment exhibited a higher ultimate tensile strength (by 34.3 MPa), higher yield strength (by 43.2 MPa), and significantly lower anisotropy, as well as improved elongations in the axial and radial directions (lower-performance directions).

Solidification microstructure of Cr4Mo4V steel forged in the semi-solid state

Semi-solid forging of iron-based alloys during solidification has unique characteristics distinct from those of the classical hot forging. With the aim of acquiring precise knowledge concerning the microstructural evolution of bearing steel Cr4Mo4V in this process, a series of semi-solid forging experiments were carried out in which samples were wrapped in a designed pure iron sheath. The effects of forging temperature and forging reduction on the grain morphology and liquid flow behavior were investigated, respectively. By forging solidifying metal (FSM), bulky primary dendrites were broken and spheroidal grains with an average shape factor of 0.87 were obtained at 1360 °C. With the decreasing forging temperature to 1340 °C, the microstructural homogeneity can be improved. On the other hand, it shows that a higher forging reduction (50%) is essential for the spheroidization of grains and elimination of liquid segregation. Those microstructural characteristics are related to different motion mechanisms of solid and liquid phases at different forging temperatures. Additionally, the effect of semi-solid forging on the eutectic carbides was also investigated, and the results demonstrate that the higher diffusion capacity and less liquid segregation jointly lower the large eutectic carbides and consequently cause its uniform distribution during FSM.

Study on Cylindrical Heatsink Forging Process Considering Friction Condition

The feasibility of forging of AL-1050 alloy of cylindrical heatsink under warm conditions is demonstrated in the present work. The stress-strain curves and friction factor play an important role in the cylindrical heatsink forging. The purpose of forging lubrication is to reduce friction between blank and die, and to decrease resistance of metal flow to die. The stress-strain curves at different temperatures are obtained by compressing tests. The friction factor between 1050 aluminum alloy and die material are determined at different temperatures by ring compression tests with graphite lubricants. The compressing and ring compressing tests are carried out by using the computerized screw universal testing machine. The finite element method is used to investigate the forming characters of the forging process. To verify the prediction of FEM simulation in the cylindrical heatsink forging process, the experimental parameters such as stress-strain curves and fiction factor, are as the input data during analysis. Maximum forging load and effective stress distribution are determined of the heatsink forging, using the finite element analysis. Finally, the cylindrical heatsink parts are formed by the forging machine under the conditions using finite element analysis.