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Magnesium die-cast alloys are known to have a layered microstructure composed of: (1) An outer skin layer characterized by a refined microstructure that is relatively defect-free; and (2) A “core” (interior) layer with a coarser microstructure having a higher concentration of features such as porosity and externally solidified grains (ESGs). Because of the difference in microstructural features, it has been long suggested that removal of the surface layer by machining could result in reduced mechanical properties in tested tensile samples. To examine the influence of the skin layer on the mechanical properties, a series of round tensile bars of varying diameters were die-cast in a specially-designed mold using the AM60 Mg alloy. A select number of the samples were machined to different final diameters. Subsequently, all of the samples (as-cast as well as machined) were tested in tension.

A study was conducted to examine the effect of solidification time and solution treatment time on the tensile properties of a 319-type aluminum alloy. Tensile samples with solidification times ranging from 0.3 to 35.5 minutes were solution-treated at 495 C for 8 hours and for 240 hours. All samples were then water-quenched and aged at 260 C for 4 hours. The tensile results show that solidification time and solution treatment time can have significant effects on the tensile properties. In general, as the solidification time increased, the ultimate strength, yield strength, and ductility decreased; increasing the solution-treatment time from 8 to 240 hours improved only the tensile strengths. The amount of Cu available in solid solution to precipitate during aging is found to be a key factor. Additionally, coarse microstructures require very long (and commercially-impractical) solution-treatment times to significantly improve the tensile strengths.

A study was conducted to determine how the fatigue life of a 319 aluminum alloy (W319) was affected by pore size. To perform this study, two sets of microstructurally similar castings with differing levels of microporosity were created. Following room temperature fatigue testing, the pores that initiated fatigue cracks were identified and quantified. The results indicate that doubling the average initiating pore diameter yielded an approximate 30% decrease in run-out stress in the W319-T7 aluminum alloy.

The automotive use of cast aluminum has greatly increased during the past decade, especially for engine blocks and cylinder heads. One physical property that is important in elevated-temperature applications is long-term dimensional stability of the cast aluminum component. Certain cast aluminum alloys (like 319) can undergo dimensional changes when exposed to engine operating temperatures over long periods of time; when these changes occur, the shape of the casting is distorted and the performance of the component may be diminished. Thus, a study was conducted to measure dimensional growth changes in a cast 319-type aluminum alloy as a function of heat-treatment, exposure temperature, and exposure time at the given temperature. The results show that all three factors have a significant effect upon the dimensional stability.

The need to increase the fuel-efficiency of modern vehicles while lowering the emission footprint is a continuous driver in automotive design. This has given rise to the use of engines with smaller displacements and higher power outputs. Compared to past engine designs, this combination generates greater amounts of excess heat which must be removed to ensure the durability of the engine. This has resulted in an increase in the number and size of the heat exchangers required to adequately cool the engine. Further, the use of smaller, more aerodynamic front-end designs has reduced the area available in the engine compartment to mount the heat exchangers. This is an issue, since the reduced engine compartment space is increasingly incapable of supporting an enlarged rectangular radiator system. Thus, this situation demands an innovative solution to aid the design of radiator systems such that the weight is reduced while maintaining the engine within acceptable operating temperatures.

The Multi Material Lightweight Vehicle (MMLV), developed by Magna International and Ford Motor Company, is a result of US Department of Energy project DE-EE0005574. The project demonstrated the lightweighting potential of a five-passenger sedan while maintaining vehicle performance and occupant safety. Prototype vehicles were manufactured and limited full-vehicle testing was conducted. The Mach-I vehicle design, comprised of commercially-available materials and production processes, achieved a 364 kg (23.5%) full-vehicle mass reduction. This resulted in environmental benefits and fuel economy improvements. A significant factor in the overall MMLV mass reduction was the decrease in the powertrain system weight from 340 kg (conventional) to 267 kg (MMLV). This enabled the application of a 1.0-liter three-cylinder engine as the main powerplant. By downsizing the engine, and by implementing material changes within the engine, the weight of the dressed engine was lowered by 29 kg.

The use of lightweight materials in automotive application has greatly increased in the past two decades. A need to meet customer demands for vehicle safety, performance and fuel efficiency has accelerated the development, evaluation and employment of new lightweight materials and processes. The 50 SAE Technical papers contained in this publication document the processes, guidelines, and physical and mechanical properties that can be applied to the selection and design of lightweight components for automotive applications. The book starts off with an introduction section containing two 1920 papers that examine the use of aluminum in automobiles.