by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
button in toolbar for more information.
Metal Casting Technologies : June 2007
TECHNICAL FEATURE www.metals.rala.com.au 22 he Intergovernmental Panel on Climate Change (IPCC) report and the Stern Review helped define the extent of the international transportation sector's contributions to global GHG emissions. Yet, in efforts at emissions mitigation, the automotive manufacturing industry has been quietly implementing changes over the past four to five decades with the use of light metal components made of either aluminium or magnesium. Long considered the 'metal of choice', aluminium shows good GHG emissions reductions. And, with the promise of resolution to its biggest handicap, magnesium looks like it is now set to give aluminium a better run for its money. But is magnesium poised to surpass aluminium in emissions and other performance standards? Release of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) in early May this year, fairly established the effects of human activity on GHG (green house gases) emissions levels and global warming. In conjunction with the Stern Review of October 2006, the two documents have indicated that the direct cost of mitigation of global GHG emissions is between 1% -3% per year of global GDP. Such figures are based on present levels of global GHG emissions of 430 parts per million (ppm) CO2 equivalent (CO2-e), and which are increasing at 2 ppm per year. Stabilisation of GHG emissions -- at whatever level -- requires that these be reduced to more than 80% below current levels. Within this context, the international transportation sector currently contributes 14% of global GHG emissions. And of this, 76% comes from road transportation, and primarily from passenger vehicles. When GHG emissions are examined on a within-country basis, China's, Australia's and the US' transportation sectors provide them 9%, 16% and 30% respectively. (See Table 1). LIGHT-WEIGHTING CARS Weight reduction through direct substitute of lighter materials to improve fuel economy and consequent savings in GHG emissions has been a routine automotive practice for sometime now. Magnesium alloys, in this respect, offer an advantage due to their lower density along with mechanical properties that can match functional capabilities offered by heavier steel and cast iron components in certain automotive applications. The resulting GHG emission performance of a magnesium engine block can be compared for directly substituting blocks made from case iron, CGI and aluminium. It can highlight the environmental advantage in using magnesium. Nevertheless, the size of this advantage can diminish, even with the application of sustainable technologies, depending on the impact of the source of magnesium used, in particular the high impact magnesium metal produced by the Pidgeon process in China. Selecting the best material for applying weight reduction, nevertheless, can be a difficult choice. Often, competition between suppliers of different materials results in improving structural performance and/or weight of materials and costs, such as the case between CGI and aluminium. Thus, choice is dictated by the relative merits of competing materials at any point in time. By Elius Levin Aluminium and Magnesium: Light-Weighting Engine Blocks and GHG Emissions T 2004 2030 2050 % Mill. Metric Tons GtCO2-e GtCO2-e Global 14 27,043~27,898 9 12 Australia 13.5-16 76.2 US 27-30 5689.2 EUR (OECD) 19 6,157 China 9 4,076 Source: APEEC 2006; Aust. Bureau Statistics Yearbook 2004; IEA 2005; Lamb 2006; WRI 2005 Table 1: Contribution of transportation sector to total GHG emissions.