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A specific objective of the European Mg-Engine project is to qualify at least two die cast Mg alloys with improved high temperature properties, in addition to satisfactory corrosion resistance, castability and costs. This paper discusses the selection criteria for high temperature alloys leading to four candidate alloys, AJ52A, AJ62A, AE44 and AE35. Tensile-, creep- and fatigue testing of standard die cast test specimens at different temperatures and conditions have led to a very large amount of material property data. Numerous examples are given to underline the potential for these alloys in high temperature automotive applications. The subsequent use of the basic property data in material models for design of automotive components is illustrated.

By selecting the right combination of alloy and processing method, a wide range of temperature exposed drive train parts can be made out of die cast magnesium, including engine blocks and automatic transmissions as probably the most demanding components. Successful new alloys for these purposes must fulfill a multitude of requirements to offer a viable solution, including mechanical properties, corrosion properties, die castability and recyclability. Therefore, selection of alloys must be based on the customers' requirements, at the same time as other factors are optimised. In this paper, results from the ongoing alloy development work by Hydro Magnesium are presented, focusing mainly on creep resistant alloys within the Mg-Al-RE system. High temperature tensile data, tensile creep-, stress relaxation- and bolt load retention results from a selection of AE alloys and reference alloys are presented.

As more and more magnesium metal is used and recycled, particularly for safety-sensitive components, the maintenance of metal cleanliness remains of critical importance. The term metal quality may be defined as 1) chemical composition 2) inclusions and porosity inside the metal, 3) the surface appearance and 4) consistency. This definition may apply to both ingots and cast parts. Chemical composition of ingots will influence on the cast parts, but also process operation at the die casters' will contribute to the chemical composition of the final product. The inclusion contents of a cast component is only indirectly determined from the cleanliness of the ingots from where it origins, emphasising the need for metal cleanliness assessment in the die casting shop. Beside the die casting process itself, the ingot surface appearance and the housekeeping in the die casting furnaces are important for the property of the product.

Eight partners from Europe and one from North America have joined efforts in a EU-supported project to find new ways for sustainable production of Mg-based engine blocks for cars. The ultimate aim of the work is to reduce vehicle weight, thereby reducing fuel consumption and CO2 emissions from operation of the vehicle. Four new magnesium alloys are considered in the project and an engine block has been series cast - 20 each in two alloys. An extensive mechanical testing program has been initiated to identify in particular the high temperature limits of the four alloys and a significant experimental study of proper bolt materials for joining is being done in parallel. Engine redesign and life cycle analysis has also been completed to secure the future sustainable exploitation of the project results. This paper presents an overview of the work and results obtained until now - 3 months before the ending date of the project.

Inclusion types and methods for inclusion assessment in magnesium and magnesium base alloys are reviewed. In pure magnesium oxides are the dominating inclusion type, while in alloys e.g. AM60 and AZ91D intermetallic particles may be equally dominant. Inclusion assessment may consist of sampling, followed by quantitative microscopy of parts of the sample, giving number size distributions and/or total contents of each particle type. In refined metal it is difficult to obtain results with statistical significance unless inclusions from a large volume are preconcentrated. In a recent method reflected light from a fracture sample is examined and inclusion content is represented by a number only. Emerging technologies include adaption of LiMCA to magnesium. No methods satisfy requirements related to rapid response, ability to distinguish between particle types, satisfactory resolution, large sample size and low cost.

Permanent mould cast medallions and 3mm die cast test plates of 47 different AZ91 based alloys covering 3-129 ppm Ni, 7-2850 ppm Cu, 87-1740 ppm Si and 0-100 ppm Co were produced. Medallions and plates were subjected to 72 hours immersion in 5% NaCl solution at 25C and to the 10 day ASTM-B117 salt spray test. The results include: a) for AZ91, the corrosion rate values anticipated from salt spray testing of die cast test plates can be calculated from the results of immersion tests on permanent mould cast medallions; b) the effect of Co on corrosion of AZ91 is 35-75 times more detrimental than Cu and thus similar to that of Ni; and c) Si showed almost no effect on the corrosion rates in the alloys examined.

The development of creep resistant alloys for automotive drive train components has proven to be metallurgically challenging. This paper discusses the principles of high temperature alloy development, featuring metallurgical, microstructural and processing aspects of some alloys, relative to their high temperature performance. The creep resistant alloys within the Mg-Al base system obtain their creep resistance by a relatively low content of Al, and addition of elements that form stable intermetallic phases within the grain mantle. Various third elements affect the high temperature performance differently. The results demonstrate that rare earth elements (RE) show a remarkable potential as the third element(s).