Aluminum Forgings Research Articles

IFHTSE Global 21: heat treatment and surface engineering in the twenty-first century Part 19 – Type I quenchants for quenching of aluminium: a review

Some aluminium forgings and castings are cold water quenched in order to achieve the desired design minimum physical properties. When unacceptable distortion or cracking is encountered, hot water has traditionally been specified as an alternative quenchant. However, hot water quenching typically results in a significant loss of mechanical properties and a significant increase in the potential for intergranular corrosion. Approximately 30 years ago, SAE designated Type I poly(alkyleneglycol) copolymer quenchants were introduced as an alternative to hot water. These quenchants offered significant, often dramatic, advantages in residual stress and distortion reduction while still achieving the Mil-Handbook 5 design minimum properties. However, even though these quenchants have been available for such a long time, there is still wide spread misunderstanding regarding how they work, when they should be used and how they should be monitored. The objective of this paper is to address these issues.

Thermo‐mechanically coupled modeling and simulation of hot metal‐forming processes using adaptive remeshing method

AbstractThe purpose of this work is to model and simulate hot metal forming processes in which material undergoes large deformations with help of the Finite Element (FE) software ABAQUS using Lagrangian formulation. Extrusion of aluminum alloys and forging of steels as two examples are taken into account in this work. To this end, a material model based on thermoelastic viscoplasticity is formulated for each case. The microstructural evolution is modeled effectively with the help of internal state variables. Element distortion and contact during the simulation of large deformation processes is controlled with the help of a custom adaptive remeshing system based on Python scripting and utilizable in commercial programs such as Abaqus. Simulation results for the microstructural development during extrusion as a func‐tion of process conditions demonstrate the sensitivity of microstructure development to these conditions. Comparison of the simulation results for the microstructure evolution with corresponding experimental results show good qualitative agreement (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Performance of Graphite and Boron-Nitride-Silicone Based Lubricants and Associated Lubrication Mechanisms in Warm Forging of Aluminum

Although water/oil-graphite emulsions are widely used in warm forging processes, they carry environmental concerns. In an attempt to replace graphite-based lubricants in warm forging of aluminum alloys, two variants of boron-nitride-silicone lubricants were formulated. The two variants were made by dispersing boron nitride powder in polydimethyl siloxane oil at concentrations of 1% and 8%. The formulated lubricants were initially tested for their thermal degradation characteristics using a thermogravimetric analyzer and compared to the thermal degradation behavior of graphite and silicone oil lubricants. Ring compression tests were then carried out at 260°C and 370°C. Boron-nitride-silicone lubricant variants did not show significant difference in performance as die temperature was increased from 260°Cto370°C. This is in contrast to graphite, which performed much better at 260°C than at 370°C, due to thermal oxidation. On the other hand, silicone oil exhibited the worst performance at 260°C and the best performance at 370°C. In both boron nitride lubricant variants, the polydimethyl siloxane facilitated hydrostatic/hydrodynamic lubrication at 260°C, with boron nitride acting as a barrier film that reduced friction. However, the lubrication mechanisms changed at 370°C, where the depolymerization of polydimethyl siloxane led to formation of silica due to thermal oxidation. Silica, together with boron nitride, acted as a film barrier with low shear strength. The dual lubrication mechanisms make boron-nitride-silicone lubricants suitable for a wide range of aluminum forging temperatures.

Characterisation of different lubricants concerning the friction coefficient in forging of AA2618

In this paper a number of aluminium forging lubricants were tested with respect to their lubricating effect and their applicability in the production of parts with long flow paths. The tests were conducted on a custom built testing machine that simulates the parameters of industrial production. The lubricants were assessed considering the change of the coefficient of friction during the test and the influence on tool and workpiece surface. From the presented analysis, the most appropriate lubricant for the investigated process was found.

Fast ribs [flexible manufacturing system

The Airbus factory in Filton, near Bristol, has invested in three Makino MAG3.H five-axis, horizontal-spindle machining centers (HMC) that form the basis of the plant's flexible manufacturing system (FMS). The HMCs are linked by a rail-guided vehicle and served by a nine-pallet handling and storage system. A twin-pallet Makino MCD2016 five-axis HMC has also been installed. The new systems produce smaller ribs for the single-aisle A320 family, the FMS being employed for machining 10 types of interspar wing rib from solid aluminum billets and extrusions, while the other MCD2016 is devoted to machining the main gear rib from an aluminum forging.

High-performance parts from steel and aluminum forgings

Classic teaching in manufacturing technology differentiates between six main groups: generating, forming, cutting, joining, coating and changing material properties [1]. Every metallic part in a car has undergone at least two, and generally several, of these main process groups. Nowadays, casting and joining are competing with bulk forming (forging) as the main contour-shaping processes. It is sometimes claimed of the processes competing with forging that they can achieve comparable material properties [2]. This information is presumably based on outdated standards for forged materials. The aim of this article by Hirschvogel is, therefore, to present the state-of-the-art when it comes to forged materials and parts.

Effect of Workpiece Anisotropy on Metal Flow and Forging Conditions in Hot Aluminium Forging

Effect of Workpiece Anisotropy on Metal Flow and Forging Conditions in Hot Aluminium Forging

The Effect of Die Geometry on Forging Conditions in Axisymmetric Hot Aluminium Forging. An Example

The Effect of Die Geometry on Forging Conditions in Axisymmetric Hot Aluminium Forging. An Example

Thermal Stress Relief in 7050 Aluminum Forgings by Uphill Quenching

A novel deep cryogenic treatment is presented to relieve residual stresses in 7050 aluminum alloy parts, in which the parts are submerged in liquid nitrogen and uphill quenched in proprietary QCW-01 quenchant. The optimum parameters of uphill quenching process were concluded in an attempt to combine maximum stress relief with the required levels of mechanical properties. The experimental results show that this novel deep cryogenic treatment can relieve as much as roughly 71% of residual stresses, higher than the traditional treatment uphill quenched in boiling water. An application example is highlighted, in which this uphill quench treatment has resulted in lower levels of residual stresses and machining distortions for an aircraft bulkhead forging.

Dry and Clean Age Hardening of Aluminum Alloys by High-Pressure Gas Quenching

When precipitation-hardenable aluminum parts are water quenched, distortion occurs due to thermal stresses. Thereby, a costly reworking is necessary, and for this reason polymer quenchants are often used to reduce distortion, with the disadvantage that the quenched parts have to be cleaned after quenching. In opposition to liquid quenchants, gas quenching may decrease distortion due to the better temperature uniformity during quenching. Furthermore, cleaning of the quenched parts can be avoided because it is a dry process. For this purpose, a heat-treating process was evaluated that included a high-pressure gasquenching step. Gas quenching was applied to different aluminum alloys (i.e., 2024, 6013, 7075, and A357.0), and tensile tests have been carried out to determine the mechanical properties after solution annealing, gas quenching, and aging. Besides high-pressure gas quenching, alloy 2024 was quenched at ambient pressure in a gas nozzle field. The high velocity at the gas outlet leads to an accelerated cooling of the aluminum alloy in this case. Aluminum castings and forgings can be classified as an interesting field of application of these quenching methods due to their near-net shape before the heat treatment. Cost savings would be possible due to the reduced distortion, and therefore, less reworking after the precipitation hardening.

Experimental and computational investigation of three‐dimensional mixed‐mode fatigue

Experimental and computational methods were developed to model three‐dimensional (3‐D) mixed‐mode crack growth under fatigue loading with the objective of evaluating proposed 3‐D fracture criteria. The experiments utilized 7075‐T73 aluminium forgings cut into modified ASTM E740 surface crack specimens with pre‐cracks orientated at angles of 30, 45 and 60° in separate tests. The progress of the evolving fatigue crack was monitored in real time using an automated visualization system. In addition, the amplitude of the loading was increased at prescribed intervals to mark the location of the 3‐D crack front for post‐test inspection. In order to evaluate proposed crack growth equations, computer simulations of the experiments were conducted using a 3‐D fracture model based on the surface integral method. An automatic mesher advanced the crack front by adding a ring of elements consistent with local application of fracture criteria governing rate and direction of growth. Comparisons of the computational and experimental results showed that the best correlation was obtained when KII and KIII were incorporated in the growth rate equations.

Powder forging of a sintered Al–3.8Cu–1Mg–0.8Si–0.1Sn alloy

The forging characteristics of an Al–Cu–Mg–Si–Sn alloy are examined using a new testing strategy which incorporates a double truncated cone specimen and finite element modelling. This sample geometry produces controlled strain distributions within a single specimen and can readily identify the specific strain required to achieve a specific microstructural event by matching the metallographic data with the strain profiles calculated from finite element software. The friction conditions were determined using the conventional friction ring test, which was evaluated using finite element software. The rheological properties of the alloy, evaluated from compression testing of right cylinders, are similar to the properties of conventional aluminium forgings. A hoop strain develops at the outer diameter of the truncated cones and this leads to pore opening at the outer few millimetres. The porosity is effectively removed when the total strain equals the net compressive strain. The strain profiles that develop in the truncated cones are largely independent of the processing temperature and the strain rate although the strain required for pore closure increases as the forging temperature is reduced. This suggests that the microstructure and the strain rate sensitivity may also be important factors controlling pore behaviour.

アルミニウム鍛造の技術動向

アルミニウム鍛造の技術動向

Textures in Aluminum Forgings

Texture and microstructure variations in a forged 7050 A1 alloy are analyzed. The results are compared to known texture effects in extrusion, shearing and plane strain deformation. Special attention is paid to locations where high local strains have been dctcted metallographically some of which show structural changes related to recrystallization and superplasticity effects. The capabilities of textures to characterize these local structures, to assess local mechanical properties and effects of unacccptable material flow are demonstrated.

ALUMINUM 6151

Abstract ALUMINUM 6151, formerly A51S Alloy, is an aluminum forging alloy combining good forgeability, strength, and resistance to corrosion. It responds to an age-hardening heat treatment. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fatigue. It also includes information on high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Al-67. Producer or source: Aluminum Company of America.