Aluminum Forgings Research Articles

Tool Surface Degradation and Adhesion in Aluminium Forging

Tool surface deterioration is a crucial effect limiting the efficiency of forging processes. Prior work on wear is limited to steel forging while investigations on tribology in aluminium forging are limited to an abstract or simplified level. The presented work aims at contributing to filling this gap with a holistic analytic approach including ball-on-disc (BoD) tests, ring compression (RC) tests and serial forging (SF) tests close to industrial applications in order to gain insights on effects and influences of surface deterioration and evaluate the suitability of different tool coatings. The results show that the primary influence on surface adhesion in aluminium forging is the superposition of surface enlargement and contact pressure of the material flow. Duplex-treated tools with the combination of a nitriding in the first step and an additional coating with chromium nitride (CrN) afterwards show a significant reduction of aluminium adhesion in ring compression and serial forging tests, representing a promising approach to tool life enhancement in forging applications.

Microstructure homogeneity regulation of 7050 aluminum forgings by surface cumulative plastic deformation

To regulate the microstructure homogeneity of large aluminum structural forgings for aircraft, the surface cumulative plastic deformation was proposed. The microstructure of 7050 aluminum forgings after the surface cumulative plastic deformation was investigated by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results showed that the microstructure evolution of 7050 aluminum forgings was more sensitive to the deformation temperature than the strain rate. The dislocation density continued to increase with the decrease of the deformation temperature and the increase of the strain rate. Dislocation density and stored energy were accumulated by the surface cumulative plastic deformation. Besides, a static recrystallization (SRX) model of 7050 aluminum forgings was established. The SRX volume fraction calculated by this model was in good agreement with the experimental results, which indicated that the model could accurately describe the SRX behavior of 7050 aluminum forgings during the surface cumulative plastic deformation.

Near Net Forming Research for Fin-Typed LED Radiator.

Pure aluminum radiator is the best choice for heat dissipation of various LED products at present. Its forming methods include common extrusion, die casting, forging, etc. Compared with other forming technologies, the LED radiator formed by cold forging has good heat dissipation performance, but there are some disadvantages in the forming process, such as uneven deformation, large material consumption and low die life. The cold forging process of pure aluminum fin-typed LED radiator is analyzed by the finite element method. The calculation results show that equal fillet structure of concave die is improper, leading to serious uneven flow velocity distribution during aluminum forging, inconsistent fin length, and warpage tendency. The gradient fillet structure of concave die is adopted. Numerical simulation and production test show that the gradient fillet structure design can significantly reduce the uneven metal flow. The extruded fins have a uniform length, which is conducive to reducing subsequent machining and production cost.

Reshaping diagrams for bending straightening of forged aeronautical components

Large and thick-walled aluminium forgings exhibit shape distortions induced by residual stresses. To restore the nominal geometry, a series of highly manual and time-consuming reshaping operations need to be carried out. In this paper, we are concerned with the development of efficient computer simulation tools to assist operators in bending straightening, which is one of the most common reshaping operations. Our approach is based on the computation of reshaping diagrams, a tool that allows selecting a nearly optimal bending load to be applied in order to minimize distortion. Most importantly, we show that the reshaping diagram needs not to account for the residual stress field, as its only effect is to shift of the reshaping diagram by some offset. That is, the overall behaviour including a realistic 3D residual stress field in a forged part can be retrieved by shifting the residual stress free reshaping diagram by the appropriate offset. Finally, we propose a strategy in order to identify the offset on-the-fly during the reshaping operation using simple force-displacement measures.

Accurate Simulation of Complex Temperature Field in Counter-Pressure Casting Process Using A356 Aluminum Alloy

Automobile steering knuckle is an important part of the steering system, which is subjected to significant impacts and loads during its operation. Generally, cast aluminum steering knuckles are usually produced using some type of enhanced low-pressure casting process, like counter-pressure casting. Compared with aluminum forging and sand cast ductile iron, it can improve the production speed and achieve the adequate casting quality. In this study, various methodologies such as dynamic thermomechanical analysis, differential scanning calorimetry, and the laser flash method were employed to study the thermophysical properties of AlSi7Mg0.3. Further, the physical model of a counter-pressure casting system with an aluminum interior was established based on the combination of the tested and the theoretical properties of aluminum; this was achieved with the consideration of the presence of other factors including rapid solidification. The temperature field of the system was computed and verified by thermocouples at six different points during the tooling and the shrinkage simulation. It was observed that the plot shape of the computed temperatures and that of the simulated ones correlated; further, the difference between the peaks and the valleys was controlled to be 3% on an average, with the maximum variation of 7% at only one point. Moreover, all the predicted shrinkages were verified by the casting. This study provides a solid foundation for facilitating the simulation of the morphologies of the microstructure.

Finite Element Prediction of Temperature Variation of Material and Dies in Aluminum Forging

Investigation into behaviors of aluminum alloy to be metal formed at the room temperature is conducted in this study. An index is used to evaluate the sensitivity of temperature, that is, index of relative normalized temperature rise to steel called normalized temperature rise index per steel which helps researchers to obtain some insight on new materials based on experiences of steel forging. An investigation to an aluminum alloy shows that the index is quite high, implying that temperature effect as well as rate-dependence effect on the forming processes of aluminum alloy at the room temperature cannot be neglected. Some details of thermomechanical predictions of a relatively high-speed automatic multi-stage forging process of a yoke with highly deformed region are given to reveal the importance of temperature and/or strain rate even in cold forging of aluminum alloy parts with high speed and high strain. All manuscripts must be in English, also the table and figure texts, otherwise we cannot publish your paper. Please keep a second copy of your manuscript in your office. When receiving the paper, we assume that the corresponding authors grant us the copyright to use the paper for the book or journal in question. Should authors use tables or figures from other Publications, they must ask the corresponding publishers to grant them the right to publish this material in their paper. Use italic for emphasizing a word or phrase. Do not use boldface typing or capital letters except for section headings (cf. remarks on section headings, below).

Модернизация установки литья и деформации металла: формирование бездефектной протяженной алюминиевой поковки

Модернизация установки литья и деформации металла: формирование бездефектной протяженной алюминиевой поковки

High Temperature Friction and Wear Testing for Closed-Die Steel and Aluminium Forgings

There are several testing methodologies to characterize the friction and wear behavior of coated or special heat treated dies and forging materials for closed-die forgings. In order to measure the friction coefficient, the wear rate, galling or fretting behavior or the effect of lubricants, three different testing types (ring compression testing, a self-made high temperature rotation tribometer and hot torsion friction) are described in detail. To meet the practical requirements, the influencing factors like temperature level, sliding speed, contact pressure and specific surface treatments or coatings have to be varied in proper ranges. The results may contribute to find better friction models for finite element analysis, and consequently to a better prediction of the material flow and other related parameters. By confocal microscopy and a full metallographic investigation, the microstructural changes near the interface are studied, which lead to a better understanding of the wear and degradation mechanisms involved. These findings may help to find out countermeasures for life time improvements of the forging dies.

Enhancement of the Young’s Modulus through Infrared Heat Treatment: A Study of the Microstructure and the Mass Effect of Real Body 6082 Aluminum Forgings

To avoid the phenomenon of abnormal grain coarsening, and increase the Young’s modulus of forgings, an infrared heat treatment was used on different mass forgings and compared with the results of an air furnace heat treatment. This work focused on the effects of microstructural evolution and the mechanical properties of two different mass 6082 real forgings. The experimental results show that infrared heat treatment can effectively reduce the mass effect after heat treatment, inhibit the coarse grains formed, and keep the non-equiaxed grains along the metal flows, thus significantly improving the ductility of the material. In addition, the rapid heating characteristic of infrared can effectively shorten the duration of heat treatment and greatly enhance the Young’s modulus and the vibration resistance of 6082 entity forgings.

Cavitation erosion behaviour of an innovative aluminium alloy for Hybrid Aluminium Forging

Aluminium alloys are commonly used for the production of components, such as cylinders, pistons, pumps, valves and combustion chambers, which in service may incur in cavitation phenomenon.In the present paper, the cavitation erosion resistance of an innovative light-alloy used for Hybrid Aluminium Forging was investigated. The material was tested by means of an ultrasonic vibratory device in compliance with ASTM G32. In order to better estimate the material behaviour, the same investigation was performed on two commercial alloys, 6061 wrought alloy and A356 casting alloy. The cavitation resistance of these materials was evaluated by determining the erosion rate from the progressive measurements of the samples mass loss during the test. The erosion mechanism was studied by means of optical and scanning electron microscope, and its correlation with the alloy hardness and microstructure was evaluated. The innovative alloy shows remarkable cavitation erosion resistance, particularly in heat-treated conditions.

Analysis of an aluminum forging process in completely enclosed dies considering the numerical prediction of thin flash generation in small gaps

In the automotive industry, aluminum forged parts must fulfill lightweight and heavy duty performance requirements. The generation of thin flash between die halves and in the small gaps between the die and punch must be prevented during the flashless forging process in completely enclosed dies. However, thin flash formation is neither predictable nor preventable. A numerical model is developed based on finite element analysis to investigate and predict the generation of thin flash in aluminum flashless precision forging processes. The significance and effects of the main influencing input parameters, including billet temperature, forming velocity, and width of gap, on different resulting parameters are evaluated. Among all resulting parameters in the established numerical model, hydrostatic pressure and the forming force in the main forming direction have been identified as the most suitable for predicting thin flash generation.

The Relationship between Occupational Noise Exposure and Noise Induced Hearing Loss (NIHL) in Small-Scale Industries: A Case Study in the City of Damavand, Iran

Background: Exposure to the excessive levels of occupational noise is one of the principal harmful agents affecting the workers’ health. This study aimed to investigate the relationship between the occupational noise exposure and the hearing loss caused by working in small-scale service industries in the city of Damavand, close to the metropolitan capital city of Tehran, Iran. Methods: This descriptive cross-sectional study investigated the occupational noise levels within the 90 small-scale industries (mainly service industries and workshops) working under the supervision of Damavand healthcare network governed by the Iranian ministry of health and medical education. A sound level meter (Bruel and Kjaer 2250) was employed to determine the noise exposure levels based on the dB A, and according to the standard ISO 9612: 2009. The audiometric exam tests were performed by an audiometer (model MEVOX SA-900). The obtained data were then analysed by SPSS 16, using linear regression and t-test. Results: The highest measured 8-hour equivalent continuous sound pressure levels (Leqs) were associated with auto body mechanics (89.2 dB A), foundry and casting workers (88.8 dB A), aluminium products fabrication workers (86.32 dB A), blacksmiths and forging (85.8 dB A) carpenters (84.93 dB A), and cabinet manufacturers, respectively (84 dB A). Results from the hearing threshold shifts of the workers from the studied occupational groups revealed that the highest work related hearing loss associated with the right ear occurred among the auto body mechanics, aluminium products fabrication workers and carpenters. However, the most significant work-related hearing loss associated with the left ear was noticed among carpenters, aluminium products fabrication workers, and auto body mechanics, respectively. Pearson correlation coefficient was tested between Leqs, work experience and hearing loss, and the results implied that the progress of workers’ hearing loss was correlated with the increase in work history and experience. Conclusions: The 8-hour Leqs and work experience were, respectively, the most important factors affecting the rate of hearing loss among the participants of this study. Keywords: Noise-Induced Hearing Loss, Sound Pressure Level, Small-Scale Industries

Investigation of tribological condition in cold forging using an optimized design of spike forging test

The spike forging test is still commonly used although there are some new tribology test methods, but each designer would like to give their own parameters. Considering the spike height difference between low friction and high friction as the evaluation index, an optimal spike forging test developed using finite element simulations based on orthogonal optimization method and sensitivity analysis of tribological conditions of selected key design parameters was carried out. The spike height does not always monotonically decrease with the increase in friction factor in the scheme with improper parameters; therefore, the design of spike forging test should be critically evaluated before assessing tribological conditions. According to the optimized parameters, a simplified set-up of spike forging test was designed, and two retainers with a clearance fit and the billet with a chamfer were prepared to position the test billet. Finally, four different tribological conditions, including dry polytetrafluoroethylene lubricant, multipurpose grease, VG32 oil, and dry condition, in aluminum forging were chosen as a case study for the optimized design of spike forging test, and correspondingly, the lubricating effect was distinguished.

Characterization of a New Aluminium Alloy for the Production of Wheels by Hybrid Aluminium Forging

Recently, an innovative technique called Hybrid Aluminium Forging (HAF) has been developed as a combination of casting and forging processes. In the present paper the characterization of a new Al-Si-Mg alloy with Cr addition is reported; it was used in a preliminary study to evaluate its suitability for the production of wheels by HAF process. At first, calorimetric analysis was performed to identify solid fraction change with temperature for process optimization. The alloy after heat treatment shows good strength and hardness, but poor ductility, while Cr modifies the morphology of Fe-containing intermetallics. Finally, rheological measurements show a shear thinning behaviour of metal in semi-solid condition.

Effects of Die Temperature on Microstructure Evolution of 7A85 Aluminum Forging

The free forging process of medium scale specimen was carried out to study the effects of the die temperature on the microstructure evolution of 7A85 aluminum forging. The results show that with the increase of die temperature, the size of the grains and the distribution of dislocations and precipitates of free forging tend to have a high degree of uniformity. Considering the effects of die temperature, the isothermal forging process was applied for the deformation of complex aviation forging. The metal flows smoothly during the isothermal forging process and thus there is little possibility of forming unfill, crack and other defects. The dislocations are evenly distributed during the isothermal forging process. Consequently, there is a relatively uniform distribution of precipitated phases of the aviation forging.

Effect of cast and extruded stock on grain structure of EN AW 6082 alloy forgings

There has been a rapid increase in the use of aluminium forgings in the automotive industry, where weight savings is a critical requirement for reduced fuel consumption and exhaust emissions. Extruded bar is the typical forging stock particularly in the manufacture of suspension components. There has been a great interest to replace the extruded forging stock with cast billets of the same diameter. The casting and extrusion routes for the manufacture of EN AW 6082 alloy forging stock were compared in the present work. The control arm produced via forging of the cast stock offers a very uniform grain structure and much superior surface quality with respect to its counterpart produced by the forging of the extruded stock owing to a much smaller grain structure at the surface of the forged component after the T6 heat treatment.

Comparison of Cast and Extruded Stock for the Forging of AA6082 Alloy Suspension Parts

High-precision near-net shape parts with excellent surface qualities can be produced with the forging process with a minimum of finishing operations thanks to the good formability of aluminium alloys. There has been a rapid increase in the use of aluminium forgings predominantly in the automotive industry, where weight savings for reduced fuel consumption and exhaust emissions is mandated by legislation. Aluminium forgings provide, in addition to low weight, high strength, good corrosion resistance and a fibrous grain structure to improve fatigue resistance. Typical commercial forging stock is the round bars produced by the extrusion of cast billets. An alternative process route that has received increasing attention in recent years is the casting of forging stock by a horizontal direct chill casting technique to make smaller billets without the need for extrusion to reduce their diameter. The anisotropy imparted to the forging stock via extrusion, often regarded as useful for the forging, is certainly missing in the former. However, cast stock has been reported to be more resistant to the formation of coarse surface grains than the extruded counterpart. The present work was undertaken to compare the casting and extrusion routes for the manufacture of 6082 alloy forging stock.

A Detailed Evaluation of the Effects of Bulk Residual Stress on Fatigue in Aluminum

The fully effective utilization of large aluminum forgings in aerospace structures has been hampered in the past by inadequate understanding of, and sometimes inaccurate representation of, bulk residual stresses and their impact on both design mechanical properties and structural performance. In recent years, significant advances in both computational and experimental methods have led to vastly improved characterization of residual stresses. As a result, new design approaches which require the extraction of residual stress effects from material property data and the formal inclusion of residual stresses in the design analysis, have been enabled. In particular, the impact of residual stresses on durability and damage tolerance can now be assessed, and more importantly, accounted for at the beginning of the design cycle.

Investigations on Residual Stress Distribution for 2A02 Aluminum Forgings

High strength aluminum alloys have been widely used in aviation manufacturing due to their favorable combination of intensity, stress corrosion resistance and toughness. However, the research and control of residual stress distribution in aluminum components have become a key issue to be solved during the heat treatment and subsequent processes. By means of the analysis of micro-indentation method and ANSYS finite element method, the residual stress distribution in 2A02 aluminum components after water quenching were systematically investigated, mainly considering two factors of the symmetry of structure and the variation of surface constraint. This study may give great help to the technology of relieving forgings residual stress of two alloys.The results of micro-indentation method show that the absolute value of the residual stress within the sample tends to decrease as the condition of constraint increase at the location of the same thickness; the absolute value of the surface residual stress also tends to decrease as the thickness of the sample increase with the same constraint conditions. The tested results by micro-indentation method are in consistent with the results of finite element simulation to a great extent.The results of finite element simulation are as follows: for these two aluminum alloy, the stress field distribution during the process of quenching is mainly influenced by the thickness of the samples. In general, at the initial stage of the quenching process, the stress state at the components surface are controlled by tensile stress in the direction of both thickness and width, while the residual stress within the samples is dominated by compressive stress; at the end of the quenching process, the stress field distribution just turn to the opposite. These results are in great agreement with the corresponding results of the indentation method.

中国のアルミニウムの鍛造技術の展望

中国のアルミニウムの鍛造技術の展望