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Newsletter "SEI NEWS" 2013

Home > Company Information > SEI WORLD > Back number > Vol.433

[Newsletter "SEI NEWS" Vol.433]

AZ91 Magnesium Alloy Sheet Employed for PC Housings

Sumitomo Electric’s AZ91 magnesium alloy sheet (“AZ91 alloy sheet”) has been employed for the housings of dynabook KIRA V832 and V632 manufactured by Toshiba Corporation. In 2010, Sumitomo Electric became the first company in the world to develop and mass-produce AZ91 alloy sheet with its proprietary casting and rolling processes. AZ91 alloy sheet has been highly evaluated and employed by Toshiba due to its (i) stamping characteristics with sophisticated design and (ii) ability to reduce thickness while maintaining high robustness. Sumitomo Electric will continue to showcase the excellent characteristics of AZ91 alloy sheet, further promoting the Group’s QCD (Quality, Cost and Delivery) improvement to expand sales in various areas.


General review of AZ91 alloy sheet

■What is AZ91 alloy sheet?

Pure AZ91 alloy sheet

The corrosion resistance of magnesium is low. To overcome this problem, the AZ91 alloy, the base material used for the development of AZ91 alloy sheet, contains about 9% aluminum and 1% zinc.

The aluminum content of 9% helps ensure sufficient corrosion resistance. However, the high aluminum content results in large alloy deposits and induces cracks in processing (rolling). Thus, the manufacture of sheet materials was considered difficult to achieve. Sumitomo Electric solved this problem by reducing the size of crystalline structures with its proprietary manufacturing process, and succeeded in developing and manufacturing a sheet material.

■What are the features of AZ91 alloy sheet?
Feature 1

AZ91 alloy sheet is as light as conventional materials, and is characterized by ever-higher strength and excellent specific strength (among the highest of the practical metals). This material also features excellent dent and impact resistance (Fig. 1).

The strength and ultimate elongation are significantly higher than those of AZ91 alloy casting material. The strength is 380 MPa (1.5 times or more that of AZ91 alloy casting material), and the ultimate elongation is 10% or more (several times that of AZ91 alloy casting material). Meanwhile, stamping workability is equivalent to that of AZ31 alloy sheet.

Fig. 1

Feature 2

The corrosion resistance of AZ91 alloy sheet is among the highest of commercialized magnesium alloys.

Feature 3

Most of the processes currently used (e.g., surface treatment, painting) are applicable. Painting and processing with sophisticated designs are also possible (Fig. 2).

The material can be painted with sophisticated designs because a wide range of paints can be used. Grinding by diamond cutting and surface treatment with metallic textures, which were considered difficult for conventional magnesium alloys, can also be achieved.

Fig. 2


Magnesium alloys are expected to be employed in various products, not only for use in electronic devices but also in vehicles and railway cars.


Sumitomo Electric was chosen as one of companies to undertake a technology development project for innovative new structural materials that the Japanese Ministry of Economy, Trade and Industry launched in FY2013.

Sumitomo Electric will develop magnesium alloy materials by enhancing both the functions, such as strength, workability, corrosion resistance, as well as cost competitiveness, in an effort to achieve drastic weight reduction of automobiles and transportation equipment.

2013 Index
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