20 - Physical Metallurgy of Light Alloys

Abstract

Improvements in energy efficiency, reduction of greenhouse gas emissions and 3R (reduce, reuse and recycle) have been one of the central topics in recent years in environment and climate change. Reducing the overall weight of the planet transportation fleet is critical to achieving these goals. It is foreseeable that, driven by environmental legislation, lightweight products will gain much wider applications in the near future. Aluminum, magnesium and titanium are all lightweight metals. At room temperature, the density of aluminum is 2.70gcm−3, which is about one-third that of steel; the density of magnesium is 1.74gcm−3, one-fourth that of steel; and the density of titanium is 4.51gcm−3, approximately 55% that of steel. Light alloys based on aluminum, magnesium and titanium have become important classes of engineering materials. Among these materials, aluminum has found the widest applications in the transportation, construction, and packaging industries. The importance of aluminum alloys is reflected by the fact that the global aluminum production reached 45 million tons in 2011. Magnesium metal has received renewed and increasingly high interest since 2000 for potential applications in the automotive, aerospace and 3C (computer, communication and consumer electronic products) industries. The global magnesium production each year was about 250,000 tons before 2000. But over the past 5 years an average of more than 650,000 tons of magnesium metal was produced each year. Most of this was used to alloy aluminum, and only 30% being used to produce magnesium alloys. Because of the lack of innovative manufacturing processes and novel alloy compositions, the mechanical and chemical properties of magnesium alloys are still inferior to those of aluminum alloys, and therefore the market for magnesium is still small compared with that enjoyed by aluminum. The global titanium metal sponge production reached 186,000 tons in 2011. Titanium alloys are mostly used in the aerospace industry, with increasing applications in the chemical and biomedical (implants) industries.