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Technical Paper

Mechanical Property Behaviour of Rheocast 319 Alloys with and without Iron Additions

2011-04-12
2011-01-1089
Cast aluminum-silicon alloys have witnessed a notable increase in use in the automotive and transport industry. The ability of these alloys to be easily cast into complex shapes coupled with a favorable strength-to-weight ratio has given them an edge over cast irons. One particular area of casting which has received further and further attention is the area of semi-solid casting, where an alloy casting is prepared as slurry with flow properties that resemble both solid and liquid. In the present work, the effects of iron additions on the mechanical properties of a 319 semi-solid alloy were studied. This alloy was prepared using the SEED process, as developed by Rio Tinto Alcan in collaboration with the Aluminum Technology Centre of NRC Canada. The SEED (Swirled Enthalpy Equilibration Device) process is a novel rheocasting method which yields a semi-solid slurry from the mechanical stirring and cooling of the molten aluminum.
Technical Paper

Compression Behavior and Energy Absorption of Aluminum Alloys and Steel for Automotive Application

2013-01-09
2013-26-0080
In this paper, energy absorption behavior of Aluminum Alloy AA 7003 and high strength steel tubes is investigated for automotive crash application both experimentally and numerically. The compression test results are compared with the static analysis results obtained from LS-Dyna Software. Tube thickness is varied in the LS-Dyna Finite Element Simulation Software to understand its effect on energy absorption behavior. The peak loads and energy absorption between experimental results and Numeral simulation are found to be in good agreement. The specific energy absorption between high strength steel and Aluminum Alloy AA 7003 is compared.
Technical Paper

Corrosion Resistance Improvement Technology of Anodic Oxide Films on Aluminum Alloy that uses a Lithium Hydroxide Solution

2013-10-15
2013-32-9049
The anodic oxide films are formed to improve the corrosion resistance on aluminum alloy that used as the parts of engines and car bodies. Because these films are porous structure, it is necessary to seal the pores to further improve the corrosion resistance. The pores are sealed with hydrated alumina by treating the films in boiling water or solution that added sealing additives. These hydration sealing has a problem that energy consumption is large because of long sealing time and high temperature of solution. In this study, the authors have developed a new sealing treatment (Lithium sealing) using a lithium hydroxide solution to solve above problem. Lithium sealing mainly sealed the pores with lithium aluminate double salt (LiH(AlO2)2·5H2O). This salt was rapidly formed in strong alkaline solution at room temperature, so that the sealing time was reduced to about 1/10 compared with the conventional sealing.
Journal Article

Effect of Chill Parameters on the Residual Strain in Cast 319 Aluminum Alloy: A Neutron Diffraction Study

2014-04-01
2014-01-0836
The demand for light weight vehicles continues to stimulate extensive research into the development of light weight casting alloys and optimization of their manufacturing processes. Of primary relevance are Aluminum (Al) and Magnesium (Mg) based alloys, which have successfully replaced selected iron based castings in automobiles. However, optimization of as-cast microstructure, processing and performance remains a challenge for some Al-based alloys. In this context, placement of chills in castings has been frequently used to locally manipulate the solidification conditions and microstructure of a casting. In this work, the effect of using an active copper chill on the residual strain profile of a sand-cast B319 aluminum alloy was investigated. Wedge-shaped castings were produced with three different cooling conditions: copper plate chill, copper pipe with cooling water and no chill (baseline).
Journal Article

Residual Stress Mapping along the Cylinder Bores of Al Alloy Engine Blocks Subjected to Production Solution Heat Treatment Schedule

2014-04-01
2014-01-0837
The development of an optimized heat treatment schedule, with the aim of maximizing strength and relieving tensile residual stress, is important to prevent in-service cylinder distortion in Al alloy engine blocks containing cast-in gray iron liners. However, to effectively optimize the engine block heat treatment schedule, the current solutionizing parameters must be analyzed and compared to the as-cast condition to establish a baseline for residual stress relief. In this study, neutron diffraction was carried out to measure the residual stress along the aluminum cylinder bridge following solution heat treatment. The stresses were measured in the hoop, radial and axial orientations and compared to a previous measured as-cast (TSR) engine block. The results suggest that solution heat treatment using the current production parameters partially relieved tensile residual stress in the Al cylinder bridge, with stress relief being more effective near the bottom of the cylinder.
Technical Paper

Friction Stir Spot Welding of a High Ductility Aluminum Alloy

2014-04-01
2014-01-0793
Abstract High ductility cast aluminum alloys are seeing more use in vehicles as a greater effort is made to replace components made from heavier steel and iron alloys with lighter weight alloys such as aluminum. High ductility cast aluminum has significant advantages by allowing for complex shape and considerable consolidation of parts in body structures. However, joining can be a challenge because one popular method for aluminum joining, self-piercing riveting (SPR), requires a ductility of greater than 10%, forcing the common high ductility Al alloys to undergo a T6 heat treatment which adds cost and potential distortion issues to Al component. In this study, friction stir spot welding was investigated as a potential joining technique for this material in the as-cast condition. Samples of as-cast Aural-2™ alloy were joined to Aural-2™, 5754, and 6061 alloys, to determine the manufacturing feasibility, weld strength, and fatigue strength using this joining technique.
Technical Paper

Creep Resistance of 2024 Aluminum Alloy

2013-10-15
2013-32-9110
Long term soaking creep rupture tests of a 2024 aluminum alloy in the T4 condition were performed at 100 °C and 130 °C under stresses ranged from 235 MPa to 370 MPa. It appears that the longer creep life can be obtained through the beneficial effect of underageing resulting in the GPB zones being retained in the matrix rather than dissolving and additional dynamic precipitation of S′ precipitates during testing; especially at the condition of 325 MPa at 100 °C, the alloy exhibits longer creep life of at least 14,604 h due to most fully developed very fine precipitates dispersion. When creep test at higher temperature (130°C), the grown S′ precipitates lead to significant reduction of creep rupture life. The correlation of applied stress, creep temperature, creep rupture time, and microstructure evolution were discussed.
Technical Paper

Development of HPDC Alloy for Motorcycle Wheel Using Recycle Aluminum

2013-10-15
2013-32-9111
The new die cast (HPDC) wheel alloy has been developed using recycled aluminum to attain considerable reduction of energy at the time of material production to make large contribution to the reduction of CO2 emissions. The material for motorcycle body parts, especially for wheels, requires a sufficient elongation property. However, when recycled aluminum, which contains large amount of impurities, is used as main raw material, the intermetallic compounds crystalize out and the elongation property is deteriorated. Accordingly, we firstly made the investigations on the elements contained in a recycled aluminum and it was clarified that the elongation property was correlated to the shape of crystallized iron-based intermetallic compounds.
Technical Paper

Advances in Numerical Investigation of Immersion Quenching at Different Pool Temperatures

2013-10-07
2013-36-0369
This paper outlines an improved computational methodology to simulate the immersion quenching heat transfer characteristics. Main applicability of the presented method lays in virtual experimental investigation of the heat treatment of cast aluminum parts, above all cylinder heads of internal combustion engines. The boiling phase change process between the heated part and a sub-cooled liquid domain is handled by using the Eulerian multi-fluid modeling approach, which is implemented within the commercial Computational Fluid Dynamics (CFD) code AVL FIRE®. Solid and liquid domains are treated simultaneously. While for the fluid domain mass, momentum and energy equations are solved in the context of multi-fluid modeling approach, only the energy equation is solved to predict the thermal field in the solid region. For the presented quenching simulation, the solid and fluid parts are contained in a single domain.
Journal Article

Cyclic Behavior of an Al-Si-Cu Alloy under Thermo-Mechanical Loading

2014-04-01
2014-01-1012
In this paper, the cyclic deformation behavior of an Al-Si-Cu alloy is studied under strain-controlled thermo-mechanical loading. Tests are carried out at temperatures from 20 °C to 440 °C. The effect of strain rate, hold time at temperature and loading sequence are investigated at each temperature. The results show that temperature has a significant effect on the cyclic deformation of Al-Si-Cu alloys. With increasing temperature, the effect of strain rate and hold time become more significant, while load sequence effects remain negligible within the investigated temperature range. Thus, an elasto-viscoplastic model is required for modeling the alloy's behavior at high temperature. This study provides an insight into the necessary information required for modeling of automotive engine components operating at elevated temperature.
Technical Paper

Development of a New High Strength Aluminum Casting Alloy for the Production of Suspension Components

2014-04-01
2014-01-0999
Abstract The Counter Pressure Casting (CPC) process is particularly suited for the production of aluminum suspension components like wheel carriers or steering knuckles. Using a typical AlSi7Mg alloy such as A356 or EN AC-42100, yield strength above 260 MPa and elongation rates above 8% are possible in a high volume production. Although these are very good values for aluminum castings, the yield strength has to be improved to increase the light weight potential of such components. The present work shows how this goal can be achieved by the development of a new aluminum casting alloy. Besides the modification of Si and Mg content, the addition of Cr leads to an additional dispersion hardening effect. In this way, yield strength above 310 MPa combined with an elongation of 7% can be assured in the CPC process after a T6 heat treatment.
Technical Paper

A Study on Corrosion Occurring at the Sealing Gap between Aluminum Alloy and Rubber Gasket

2014-04-01
2014-01-0997
Abstract ADC12 is one of the common aluminum alloys for automobiles because it has suitable for casting and machining. However, the corrosion resistance of ADC12 is insufficient in comparison with other aluminum alloys. The corrosion depends on chemical composition of aluminum and circumstance around aluminum. It was considered that a crevice such as a seal gap accelerates corrosion rate. Therefore, the corrosion at a sealing gap between ADC12 and rubber gasket was investigated. Salt water corrosion tests were carried out with an o-ring compressed between ADC12 plate and plastic plate. Corrosion depth and corrosion area at sealing surface were measured with a microscope. The corrosion depth at the sealing surface was deeper than that outside it. Since smooth surface of aluminum prevented the sealing surface from corrosion, it was considered that the narrow sealing gap enabled to decrease in the corrosion rate.
Technical Paper

Development of Lead-Free Al-Sn-Si Alloy Bearing for Recent Automotive Engines

2014-04-01
2014-01-0995
Abstract With increased awareness of environmental issues and regulations, developments for recent automotive engines are progressing towards engines with low fuel consumption. Due to these changes, automotive engine bearings are increasingly used in harsher environments, with higher loading. These operating conditions require bearings with both conformability and fatigue resistance. From the above background, various aluminum alloy bearings have previously been developed, including materials with solid solution treatment to improve their properties, and alloys which can be used with or without an overlay [1, 2, 3]. These materials are known to have good conformability and fatigue resistance. However, while conventional Al-Sn-Si alloy bearings display excellent sliding properties, due to the unceasing trend for engine downsizing, more conformability is required.
Technical Paper

On Modeling the Hot Stamping of High Strength Aluminum Sheet

2014-04-01
2014-01-0983
Abstract This paper documents the finite element (FE) analysis of a hot stamping process for high strength aluminum sheet. In this process a 7075 blank, heated above its solvus temperature, was simultaneously die quenched and stamped in a room temperature die to form a B-pillar outer reinforcement. Two modeling approaches have been investigated: an isothermal mechanical model and a non-isothermal coupled thermo-mechanical model. The accuracy of each approach was assessed by comparing the predicted strain and thickness distributions to experimental measurements from a formed panel. The coupled thermo-mechanical model provided the most accurate prediction.
Technical Paper

Experimental Evaluation of the Quench Rate of AA7075

2014-04-01
2014-01-0984
Abstract The aluminum alloy 7075-T6 has the potential to be used for structural automotive body components as an alternative to boron steel. Although this alloy shows poor formability at room temperature, it has been demonstrated that hot stamping is a feasible sheet metal process that can be used to overcome the forming issues. Hot stamping is an elevated temperature forming operation in which a hot blank is formed and quenched within a stamping die. Attaining a high quench rate is a critical step of the hot stamping process and corresponds to maximum strength and corrosion resistance. This work looks at measuring the quench rate of AA7075-T6 by way of three different approaches: water, a water-cooled plate, and a bead die. The water-cooled plate and the bead die are laboratory-scale experimental setups designed to replicate the hot stamping/die quenching process.
Journal Article

Fatigue Behavior of Aluminum Alloys under Multiaxial Loading

2014-04-01
2014-01-0972
Fatigue behavior of aluminum alloys under multiaxial loading was investigated with both cast aluminum A356-T6 and wrought alloy 6063-T6. The dominant multiaxial fatigue crack preferentially nucleates from flaws like porosity and oxide films located near the free surface of the material. In the absence of the flaws, the cracking/debonding of the second phase particles dominates the crack initiation and propagation. The number of cracked/debonded particles increases with the number of cycles, but the damage rate depends on loading paths. Among various loading paths studied, the circle loading path shows the shortest fatigue life due to the development of complex dislocation substructures and severe stress concentration near grain/cell boundaries and second phase particles.
Journal Article

Hot Stamping of a B-Pillar Outer from High Strength Aluminum Sheet AA7075

2014-04-01
2014-01-0981
This work demonstrates the feasibility of hot stamping a B-pillar outer panel from aluminum alloy 7075. AA7075 is characterized by a high strength to weight ratio with yield strengths comparable to those of DP and TRIP advanced high strength steels. Applications using AA7075 have typically been limited to the aerospace industry due to the high variable cost associated with forming and joining of these materials. A primary key to implementation in the automotive industry is the development of metal forming methods that produce non-compromised stamped parts at automotive manufacturing volumes and costs. This work explores the feasibility of die quenching a hot blank within a cold die as a means of delivering high strength aluminum sheet parts. A die made from kirksite was used to evaluate the hot stamping process for a B-pillar outer. After the forming/quenching operation, the parts were subjected to an artificial aging process to regain the properties of the T6-temper.
Technical Paper

Effect of Surface Roughness and Sliding Velocity on Tribological Properties of an Oxide-Coated Aluminum Alloy

2014-04-01
2014-01-0957
Abstract Aluminum engines have been successfully used to replace heavy gray cast engines to lighten the car's weight and reduce the fuel consumption. To overcome the aluminum alloys' poor wear resistance, cast iron liners and thermal spraying coatings were used as cylinder bore materials for wear protection. A plasma electrolytic oxidation (PEO) technique had also been proposed to produce an oxide coating on aluminum cylinder bore. The oxide coating can have a low coefficient of friction (COF) and minimum wear shown in the lab tests. To conserve more fuel, the stopping and restarting system was introduced when the vehicle was forced to stop immediately for a short time. When the engine was forced to stop and restart, the reciprocating speed of the piston was very slow, and the friction between the piston and the cylinder was high. In this research, a pin-on-disc tribometer was used to investigate tribological behavior of the oxide coating on an aluminum alloy.
Technical Paper

Semi-Solid Casting of Magnesium and Aluminum Alloys via the CRP (Continuous Rheo-conversion Process)

2006-04-03
2006-01-0509
Semi-solid processing (SSM) has many advantages in that the alloy is cast at lower temperatures (i.e., in the two-phase region) giving rise to reduced die wear, as well as giving rise to novel microstructures. The resultant SSM processed castings are dendrite-free and do not contain hot tears; rather, the SSM structure is globular, and the liquid phase surrounding the globules acts as a “lubricant” during processing. Moreover, the flow of the slurry into the die cavity is more laminar than turbulent, since the starting metal is in the mushy region. This concept of SSM processing was realized by the development of a continuous process titled: CRP - Continuous Rheo-conversion Process. In this process, one allows the incipient solidification of alloy melt(s) under the combined effects of forced convection and rapid cooling rates. In the CRP, two liquids held at particular level of superheat, are passively mixed within a reactor.
Technical Paper

High Cycle Fatigue of Cast Aluminum Alloys at Ultrasonic Frequency

2006-04-03
2006-01-0540
Ultrasonic fatigue testing machines working at approximately 20 kHz allow extending the number of testing cycles to the 108-1010 range, which would be prohibitive using conventional servo-hydraulic machines (up to 100 Hz). One of the questions that arise, however, is if the results from these very high frequency tests are comparable to the ones obtained from conventional tests performed at lower frequencies. This paper compares the high cycle fatigue (HCF) behavior of four cast aluminum alloys under two test frequencies (75 Hz and 20 kHz). It is shown that the S-N curve for some alloys is very sensitive to the testing frequency.
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