Traditional Japanese swords have typically been forged using high-carbon steel known as tamahagane steel. During the country's feudal period, specifically during the Kamakura era, Japanese bladesmiths discovered that adding coal to steel created a new, stronger type of metal. This led to the use of tamahagane steel as being the preferred metal in which high-quality swords like the katana, wakizashi and tachi were made. But not all Japanese swords were made using tamahagane steel. The iaito, for example, was made using an aluminum-zinc alloy metal. So, why did bladesmiths choose aluminum-zinc alloy for the iaito instead of tamahagane steel?
Overview of the Iaito
To better understand why Japanese bladesmiths constructed the iaito out of aluminum-zinc alloy, you must look at the origins and purpose of this sword. The iaito wasn't an ordinary traditional Japanese sword intended for combat usage. Rather, it's a special type of Japanese sword that's used primarily in martial arts competitions.
The Japanese martial art iaido, specifically, is widely practiced using the iaito. During iaido, practitioners unsheathe and draw their sword as quickly as possible. It's not a combative martial art in which practitioners directly engage each other. Iaido is generally performed a solo-style martial art where practitioners project their ability to respond to potential attacks by unsheathing and drawing their sword, with the iaito being the most common type of sword using for this purpose.
Aluminum-Zinc Alloy Is Cheaper Than Steel
One of the reasons aluminum-zinc alloy is used to make the iaito instead of steel is because it costs less. Steel is a readily available metal that's found in many countries throughout the world. In Japan, though, local steel has been somewhat scarce throughout much of the region's history, prompting bladesmiths to find and use alternative metals for non-combative swords, such as aluminum-zinc alloy. Consisting of aluminum and zinc, this alloy metal costs a fraction of the price of steel.
Aluminum-Zinc Alloy Is Lighter Than Steel
In addition to being cheaper than steel, aluminum-zinc alloy is also lighter than steel. In most cases, aluminum-zinc alloy is about one-third the weight of steel. The alloy's lightweight properties make is an excellent choice for iaito swords since these swords are designed primarily for use in martial arts like iaido. Having just one-third the weight of a steel sword, practitioners can easily draw and unsheathe iaito swords made of aluminum-zinc alloy.