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Technical Paper

Design of As-Cast High Strength Al-Si-Cu-Ni-Sr Alloys Using the Taguchi Method

In the present study, a design of experiment (DOE) technique, the Taguchi method, was used to develop as-cast high strength aluminum alloys with element additions of Si, Cu, Ni and Sr. The Taguchi method uses a special design of orthogonal arrays to study all the designed factors with a minimum of experiments at a relatively low cost. The element factors chosen for this study were Si, Cu, Ni and Sr content in the designed aluminum-based alloys. For each factor, three different levels of weight percentages were selected (Si: 6, 9, 12%, Cu: 3, 5, 7%, Ni: 0.5, 1, 1.5% and Sr: 0.01, 0.02, 0.03%). Tensile properties such as ultimate tensile strength, yield strength and elongation at failure were selected as three individual responses to evaluate the engineering performance of the designed alloys. The results of the factor response analysis were used to derive the optimal level combinations.
Journal Article

Fusion Welding of Vacuum High Pressure Die Cast Aluminum Alloy A356 and Wrought Alloy 6061

Recently, joining of cast aluminum components with wrought and/or cast similar metals becomes an urgent task for the auto industry to develop light-weight complex and large-scale chassis and body structures for further reduction in vehicle weight. In this study, fusion-joining of vacuum high pressure die cast (VHPDC) alloy A356 subjected to T5 heat treatment and wrought alloy 6061 with the Gas Metal Arc Welding (GMAW-MIG) process was experimented in an effort to understand the effect of the MIG process on the microstructure development and tensile behaviors of the base alloys (T5 A356 and 6061), Heat Affected Zone (HAZ) and Fusion Zone (filler metal ER4043). The results of tensile testing indicated that the ultimate tensile strength (UTS), yield strength (YS) and elongation (Ef) of VHPDC T5 A356 were relatively high, compared to both wrought alloy 6061 and the filler metal (ER 4043).
Journal Article

Wear Protection of Al383/SiO2 Metal Matrix Composites by Plasma Electrolytic Oxidation (PEO) Process

Al383/SiO₂ metal matrix composites (MMC) were designed to increase the wear properties of the Al alloy. However, the soft Al matrix was subject to large plastic deformation under high normal load during lubricated sliding wear tests, causing detachment of the reinforced particles. To further increase the wear resistance of the MMC, in this research, Plasma Electrolytic Oxidation (PEO) process was used to form oxide coatings on the MMC. The hard and wear-resistant oxide coatings protected the metal matrix during the wear tests, reducing the wear rate of MMC. The effect of both oxide coating thickness and volume content of SiO₂ particles on the wear behavior of MMC was investigated. It was found that with a proper combination of the volume content of SiO₂ and coating thickness, the MMC exhibited high wear resistance and low friction coefficient.
Technical Paper

Development of Hybrid Magnesium-based Composites

In the past decade, magnesium (aluminum) alloy use in the automotive industry has increased in order to reduce vehicle weight and fuel consumption. However, their applications are usually limited to temperatures of up to 120°C. Improvements in the high-temperature mechanical properties of magnesium alloys would greatly expand their industrial applications. As compared to the unreinforced monolithic metal, metal matrix composites have been recognized to possess superior mechanical properties, such as high elastic modulus and strengths as well as enhanced wear resistance. In this study, a novel approach of making hybrid preforms with two or more types reinforcements, i.e., different size particles and fibers, for magnesium-based composites was developed. An advanced and affordable technique of fabricating hybrid magnesium-based composites called the preform-squeeze casting was employed successfully.
Technical Paper

Microstructure Influence on the Corrosion of Permanent Mould Cast Magnesium Alloy AJ62 in Engine Coolant

Powertrain applications of alloy AJ62 arose from its comparative resistance to high temperature deformation among magnesium alloys. In this research, AJ62 permanent-mould cast in different section thicknesses was subjected to immersion corrosion in commercially-available engine coolant. The objective was to determine corrosion behaviour variation among casting thicknesses. Corrosion product accumulation suggests passive film formation, and unlike in other media, the film exhibits certain stability. Extreme thicknesses were used to generate polarization curves for their respective microstructures in engine coolant. Variation with casting section thickness was observed in the curves. These preliminary results indicate coarsened microstructures reduce corrosion resistance of the permanent mold cast AJ62 alloy.
Journal Article

Rotary Fatigue Analysis of Forged Magnesium Road Wheels

Fatigue analysis incorporating explicit finite element simulation was conducted on a forged magnesium wheel model where a rotating bend moment was applied to the hub to simulate rotary fatigue testing. Based on wheel fatigue design criteria and a developed fatigue post-processor, the safety factor of fatigue failure was calculated for each finite element. Fatigue failure was verified through experimental testing. Design modifications were proposed by increasing the spoke thickness. Further numerical and experimental testing indicated that the modified design passed the rotary fatigue test.
Technical Paper

A Post-processor for Finite Element Stress-based Fatigue Analysis

Explicit finite element simulations were conducted on an aluminum wheel model where a rotating bend moment was applied on its hub to simulate wheel cornering fatigue testing. A post-processor was developed to calculate equivalent von Mises alternating and mean stresses from stress tensor. The safety factors of fatigue design for each finite element were determined to assess the fatigue performance by utilizing the Goodman linear relationship. Elements with low safety factors were identified due to the prescribed boundary conditions and stress concentrations arising from wheel geometry.
Technical Paper

Kinetic Energy Compensation of Tire Absence in Numerical Modeling of Wheel Impact Testing

Impact characteristics of aluminum wheels are evaluated in accordance to the testing procedure SAE J175. In an effort to simplify the numerical modeling of wheel impact testing, numerical analysis has been conducted to investigate the percentage of the striker kinetic energy absorbed by the tire during the impact test. 10%, 15%, 20%, 25%, and 30% reductions of the striker kinetic energy were computed in order to assess the appropriate percentage reduction. Comparisons of wheel plastic deformations of both experimental and numerical methods illustrate that a 20% reduction in the striker kinetic energy provides an effective approach to simplify the modeling.
Technical Paper

Creep and Bolt Load Retention Behavior of Die Cast Magnesium Alloys for High Temperature Applications: Part 2 of 2

The effect of calcium on the creep and bolt load retention (BLR) behavior of AM50 alloy has been investigated. Four AM50 alloys 0, 0.25, 0.56, and 0.88% Ca have been die-cast. BLR-tests have been conducted at 125, 150, and 175°C and preloads of 14, 21, and 28kN. Tensile and compressive creep tests were also conducted at 150°C and initial stresses from 40 to 80 MPa. Both creep and BLR were significantly influenced by calcium content, with increasing calcium content resulting in improved relaxation resistance. The BLR of AM50 with 0.88% Ca was better than that of AE42 at all temperatures although the effect of calcium was temperature dependent. Calcium did not change the sensitivity of BLR to preload, while it increased the relaxation limit (Fr) of AM50 significantly. In addition, calcium improved the creep resistance of AM50 significantly.
Technical Paper

Die Castability Assessment of Magnesium Alloys for High Temperature Applications: Part 1 of 2

This paper describes the high-pressure die castability assessment of two high temperature magnesium alloys, AE42 and the AC series alloy. AE42 is a commercially available alloy. Results showed that AE42 was a castable material for use in high-pressure die casting applications, including large transmission components. AE42 was determined to have similar operating/manufacturing costs if produced in equivalent volumes to AZ91D. The AC series alloy is an experimental alloy comprised of AM50 combined with small percentages of calcium (Ca). It was found that the castability of the AC series alloy decreased with increasing calcium content. Over 0.3% calcium content yielded poor castability performance. Selected mechanical and corrosion properties of AZ91D, AE42, AM50 and the AC series alloys were also explored.