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The development of commercial magnesium die casting alloys has progressed over the past several decades. The most commonly used die casting alloy, AZ91D, with 9% aluminum content, has been and still is used in the majority of structural automotive applications. New magnesium alloys have been developed in the past several years to meet the needs of structural applications that require an appreciable amount of creep resistance and improved stress relaxation performance during service. Typical applications would include powertrain components. This paper provides further mechanical property data on the “AE-Type” magnesium alloys. These alloys consist primarily of aluminum and rare-earth additions to magnesium to increase creep resistance and stress relaxation performance attributes of the base metal. However, changes in tensile strength, elongation, etc. may also be realized.

The compatibility of magnesium die casting alloys with commercial automatic transmission fluids was studied in laboratory tests. The effects of high temperature, presence of water, and galvanic coupling with steel were examined, using visual observation, weight change, Scanning Electron Microscope, and Scanning Auger Microprobe surface analysis. No significant corrosion of magnesium was detected under any of the test conditions.

The development of commercial magnesium die casting alloys has progressed over the past several decades. The most common die casting alloy, AZ91D with 9% aluminum content, has been and still is used in many structural automotive applications. New magnesium alloys have been developed in the past several years to meet the needs of structural applications that require an appreciable amount of energy absorption during service. Magnesium alloys having lower aluminum content, such as AM50 and AM20, were developed by Norsk Hydro and found to be more ductile, especially during impact situations. Their immediate use was focused towards applications such as automotive seat frames and instrument panel/cross-car beams. This paper provides mechanical property data on the “AM-Type” magnesium alloys. These alloys consist primarily of aluminum and manganese additions to magnesium to increase the energy absorption attributes of the base metal.

The advancements and expanded usage of magnesium by the automotive industry are highlighted in this publication which contains 46 SAE Technical Papers presented by technology experts at SAE events from 2001 -2005. This information will aid in improving processes, developing new applications, and identifying new technologies to further the competitive edge of magnesium as a lightweight, recyclable, and viable metal to meet global automotive needs. An increased awareness of the benefits ands features of this light weight structural material has opened a wide range of applications within the automotive industry. Examples include instrument panel structures, seat frames, center consoles, transmission cases, front-end and radiator support structures, and hybrid magnesium powertrains. The advancement continues toward developing even higher-performing alloys to further the competitive edge of magnesium.

Selected metallic platings and insulating coatings on steel fasteners were evaluated for ability to reduce galvanic corrosion of die cast magnesium in a modified salt spray test. Proprietary electroplate systems based on zinc, zinc-nickel, zinc-cobalt and tin-zinc were tested, along with a commercial 50-50 tin lead alloy electroplate without supplementary coating. A proprietary liquid-applied zinc-rich inorganic coating successfully used on automotive fasteners was also tested for compatibility with magnesium. Encapsulation of bolt heads with plastic insulating coatings or special molded caps was evaluated. Interruption of the continuous salt spray by rinse and bake cycles was investigated as a likely exposure condition for magnesium assemblies in powertrain or underhood applications. Several of the protection schemes were found to effectively eliminate galvanic corrosion of the magnesium.

This paper describes the methodology by which a combination die cast magnesium and extruded aluminum door frame was developed using a current production steel door design as the base model for comparison. Product performance data, such as side impact requirements and overall door stiffness, along with the packaging of existing internal hardware, is presented. The results are verified by computer modeling. A prototype casting was produced to validate and compare castability requirements and geometry constraints of the door frame. An economic study is included that investigates the potential of developing such a system suitable for production. The results suggest that economic benefits may be obtained by using such a lightweight door system compared to an existing steel door design.

During the last several years the use of magnesium die-castings for automotive applications has been on the rise. Magnesium's use in die-cast form has been expanding at an average growth rate of more than 15% a year. Reasons for the increase are both practical and economic. Magnesium die-castings offer components having the lowest mass when compared to almost any other structural material. Magnesium die-alloys exhibit properties that bridge the gap between engineered plastics and metals. The mechanical performance ratios (strength-to-weight and stiffness-to-weight) of magnesium also compete favorably with metals and plastics. Economically, magnesium alloys prices have fallen during the last several years making them extremely competitive with other materials.