Materials Science Forum Vols. 618-619

Abstract: The lightness of magnesium makes it an attractive material for applications where weight reduction is critical, in particular, consumer electronics and transportation industries. Despite its advantages as a material the use of magnesium worldwide is a tiny fraction of other materials (steel, plastic, aluminium). Amongst the reasons for this, the metal’s price has not been a significant factor until recently. Throughout the period of 2001-2006, magnesium has been cheaper than both aluminium and zinc on a volumetric basis. An issue that magnesium presently faces is a perceived insecurity of supply. 77% of primary magnesium is produced within China and the price has seen some enormous shifts. In late 2005 the magnesium price (primary FOB China) was about 1500USD/t. By the third quarter of 2008 it had risen to over 6000USD/t only to fall in recent month to below 3000USD/t. The current pricing levels of around 3000USD/t could prove beneficial if maintained over a long period, if it led to the establishment of new producers and a diversification of the supply base.

Abstract: By 2050 the world population will reach over nine billion and “flattening of the world” will be an understatement. We anticipate burgeoning needs regarding energy resources, transportation, housing, food distribution/packaging for the masses, recycling, and health care/ health care delivery, not to mention climate change and environmental issues. World population is increasing at an average rate of 1.4%, and in contrast world energy consumption is increasing at an average rate of 1.7%. Such an imbalance is not sustainable. From a societal perspective, engineers have played a major role to enhance the quality of life in our world. Sustainable development in the 21st Century is perhaps the most critical issue we face. This keynote will address the solutions that light metals technologies bring to the table to meet these challenges. The opportunities for processing and component manufacture to address these challenges will be reviewed and discussed.

Abstract: Companies and research organizations in the aluminium industry have a number of different strategies for protecting their new developments. Many research organizations have a patent focused strategy to facilitate commercialization of their new technologies. Conversely, primary aluminium producers tend to use patent protection more selectively, as they are able to use other Intellectual Property protection means such as trade secrets to protect their developments. This paper provides an overview of international patent publications from 1995 to 2008 in the field of electrolytic aluminium production and comments on perceived factors driving IP protection of these developments.

Abstract: Light weighting of cars has the definite advantage of reducing fuel consumption and tail pipe emissions. In this respect, substitution of heavier steel components with magnesium ones can save on weight of the replaced component due to its weight advantage resulting in lowering green house gases (GHG). There are additional benefits when magnesium is applied to complex structures and assemblies such as an Instrument Panel (IP). The possibility of casting single piece magnesium cross-car beams of IP can reduce the number of components to be assembled as wells as ease the disassembly and recovery at the end of life. This study, considering these advantages of using magnesium for IPs, examines and compares the environmental life cycle impact of magnesium and traditional steel and plastic IPs. However, the results indicate that magnesium IPs can have higher GHG impact than equivalent IPs made from others. The technological avenues for reducing the impact of magnesium IPs are examined in an extended study, including impact of primary metal (assumed from China), improvements in casting manufacture and use of secondary metal. These improvements show substantial reduction of GHG in the manufacture of magnesium IPs and improvement in comparative GHG performance with other materials.

Abstract: In spite of die castings being amongst the highest volume items manufactured by the metalworking industry, the influence of high pressure die casting (HPDC) process parameters on greenhouse gas (GHG) emissions remains largely unreported. In this article, the authors discuss the effect of some HPDC process parameters on GHG emissions using cradle-to-gate life cycle assessment (LCA) for both aluminium and magnesium alloys. Although the impacts reduced with increasing yields in both cases, it was determined that the GHG impact of magnesium alloy HPDC was more sensitive to HPDC yield irrespective of the ratio of primary/secondary alloys in the melt charge. The reasons for this include a greater dependence of magnesium alloy HPDC on high-emitting primary processing and the use of the highly potent GHG SF6 for melting. For magnesium alloy HPDC, a decrease in quality assurance (QA) rejects and cycle times also reduced GHG emissions, although their influences were found to be an order lower than that of yield.

Abstract: ATM high pressure die casting technology (ATM) is a variant of the traditional high pressure die casting (HPDC) process and is distinguishable by its characteristic lean runners that increase process yields. Reduced raw material consumption helps ATM leave a smaller footprint on the environment by lowering greenhouse gas (GHG) emissions during primary processing of the alloys and in their melting and handling in the foundry. Further avenues for reducing GHG emissions are raised by the use of ATM technology which improves the integrity of castings - facilitating the adoption of lighter weight components in automobiles. In the present paper, reductions in GHG emissions achieved by ATM are illustrated with the aid of a commercial case study; potential mass reduction opportunities for the automotive sector are explored with the aid of finite element analysis.

Abstract: Melt flow and solidification within a die casting cavity is a complex process dependent in part on melt pressure (with or without intensification), melt velocity, melt flow path, thermal gradients within the die, die lubrication and melt viscosity. Casting defects such as short shots, cold shuts and shrinkage porosity can readily occur if casting conditions are not optimised. Shrinkage porosity in particular is difficult to eradicate from castings that comprise thick sections, since these sections will usually solidify late in the casting cycle and may be starved of melt supply during the critical solidification (and contraction) stage. The current work seeks to elucidate the influence of the melt shearing on the die casting process and demonstrates that the modifications made to the melt through introduction of a local constriction in the melt path can generate improvements in casting microstructure and reduce shrinkage porosity.

Abstract: The present investigation is aimed at evaluating the influence of tool rotation rate and welding speed on the microstructure, tensile properties, and fracture mode of 6061 Al-T651 alloy after friction stir welding (FSW). TEM results revealed that in the nugget zone (NZ), FSW resulted in the dissolution of fine needle-shaped precipitates that previously existed in the base metal. At a given rotation rate of 1400rpm, the yield strength (YS) and ultimate tensile strength (UTS) of the welded joints increased with increasing welding speed from 200 to 600mm/min. However, the UTS of the joints was nearly independent of the rotation rate. Furthermore, the relationship between the hardness distribution and fracture location has also been identified.