“Sometimes in life, you will find that you must let things go simply because they are heavy.” Of course, we are talking about the metal, steel, and aluminum market. We’re editors for an aluminum extrusion company, after all – so our primary interest is focusing on lightweight aluminum and where lightweight aluminum alloys stand in regard to the lightweight revolution that has infiltrated virtually every industry involving buildings, infrastructure systems, technology and transportation over recent years.
Everything is becoming lighter. Planes, trains, automobiles, and even Apples. (We know which Apples.) The reason for “lightweighting” is obvious: lower costs, smaller carbon footprint, stronger, more robust and corrosion-resistant products, and the big one… better fuel economy. So how does lightweight aluminum fit into the picture? What are the “aluminum alloys to be reckoned with?” Are we going to find these super strong lightweight aluminum alloys in everyday items like bridges or automobiles?
Nope. Unless you’re an astronaut. Aerospace is where you’ll find 2XXX and 7XXX alloys. Military applications are a distant second. And not even a speck in the rearview mirror? Auto.
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2XXX and 7XXX are the name of the game when it comes to “strong and light.” 2XXX alloys are aluminum-copper. Adding lithium to the mix creates an even higher strength alloy – AA2195 is one example. You’ll find these in Boeing airplanes and SpaceX rockets… but not in automobiles… lithium is expensive. Which is why 7000 series alloys are being considered for the automotive sector, but may not be as lightweight as the lithium-containing 2000 series alloys. (A glimpse of perspective: The only mass-produced aluminum is beverage cans, and that is 3XXX for the body and 5XXX for the top/lid.) The challenge to be met regarding 7XXX for automotive use is formability. 7XXX series alloys really like to remain flat, and testing techniques such as high temperature forming are expensive and slow. A rough comparison: 1 day of auto production = 1 year of airplane production.
Currently the strongest lightweight aluminum alloys are going to be found in low volume applications only. “Warm forming” of 2XXX and 7XXX can be found in aerospace and not automotive because the slower manufacturing process combined with the extra expense of alloying and energy (heating the metal and/or the tooling) are relatively low in aircraft manufacturing. This process has a significantly higher percentage of total costs when it comes to manufacturing an automobile. So, friends, it’s going to be a while until we see 7XXX in cars, and due to its expense, 2XXX will likely remain an aluminum alloy that stays in the sky.
Aluminum alloyed with anything after it on the periodic table will be heavier than pure aluminum. Aluminum alloyed with anything before it will be lighter. The further before, the greater lightweighting. Which is why Al-Li (lithium) are the lightest aluminum alloys.
A very special thank you to Daniel J. Schaeffler, Ph.D., President and CEO of Engineering Quality Solutions, for lending your thoughts, opinions, and pun ideas to our blogs.