subject: Why Zinc-aluminium Die Casting Alloys Are So Popular [print this page] There has been a rise in the popularity of zinc-aluminium (ZA) casting alloys for use in a number of industries over the last few years, mostly because they give the metal superior mechanical properties that they could not possess otherwise and because the alloys are much stronger, harder and creep resistant than either zinc or aluminium is by themselves. The alloys of note here include: ZA-8, ZA-12, and ZA-27.
The reason behind the creation of these zinc-aluminium alloys was largely because it was hoped that they would be able to replace 1350 EC alloy for creating electrical circuits (as the EC alloy was known to gradually loosen, which led to overheating). With the use of zinc-aluminium circuits, however, this problem has been completely solved without sacrificing any of the conductivity the metal is known for.
Wire that is made out of 1350 EC (commonly used in binding screw terminals) was also known to possess a number of problems, including: loosening and expanding over time (caused by the wire heating up as it gets overloaded); and contracting and oxidization (caused by the wire cooling). As these cycles continue, the wire will be continuously overheated and cooled until finally it fails and is completely useless. With the use of the zinc-aluminim alloys, on the other hand, these additional failures are less likely to occur, thanks to the wire having a better microstructural stability.
So, how are zinc-aluminium alloys processed and their amazingly strong microstructure created?
To begin with, a continuous casting process produces a bar of around 50 centimetres square on a 2.5 metre copper wheel. The quick solidification of the metals results in a dendrite arm spacing and a eutectic red spacing (containing a supersaturation of iron that is at around 0/1%); these particles are actually what gives stability to the substructure of the zinc-aluminium alloy.
Then, the bar is heated rapidly. When the temperature has risen to around 450 degrees Celsius, the hot worked metal is put through a cold rolling process in order for it to obtain cold yield strength. The cold yield strength enables both the zinc and the aluminium to inherit (or carry forward) properties from their original states, aiding to increase the density of their walls.
As you can see, the strength that is available when an alloy of zinc and aluminium is created is a huge advantage and a big enticement for using the alloy in place of other materials. If you are ever given the choice between a solitary metal and an alloy that contains these great friends of aluminium and zinc, what will your choice be?
