We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is Age Hardening?

By John Markley
Updated May 17, 2024
Our promise to you
About Mechanics is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At About Mechanics, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

Age hardening is a type of heat treatment used in metallurgy to strengthen metal alloys. It is also called precipitation hardening, as it strengthens metal by creating solid impurities, or precipitates, in the alloy that prevents dislocations in the alloy's crystalline structure. Its name comes from the point in the hardening process in which the metal is aged, either by heating it for an extended of time or keeping it stored at a lower temperature for an extended period before use so that these precipitates can form. This treatment is used on malleable alloys, such as those made from nickel, magnesium, and titanium, as well as some types of steel.

Metal undergoing age hardening is heated to a high temperature, which varies according to the materials being used and the desired properties of the final result. For example, maraging steel is heat treated at about around 1510°F (about 820°C). Alloying materials are added and allowed to diffuse through the metal until the heated metal is supersaturated with them, meaning that the amount of these materials dissolved in the metal is higher than would be possible for a solid solution at room temperature.

Next the metal is aged. In some alloys, this is done by keeping the metal heated for several hours at a temperature lower than that of the initial phase but still much hotter than room temperature. Other alloys are stored for days or weeks at room temperature. At lower temperatures, it is no longer possible for all of the alloying materials to remain dissolved in the supersaturated metal, and so some of it undergoes precipitation and separates from the solid solution, becoming impurities spread throughout the metal. The temperature at which the aging process occurs affects how this precipitation occurs, and so influences the mechanical properties of the resulting alloy.

These impurities created by the hardening process strengthen the metal by interfering with the movement of crystallographic defects called dislocations, which result from misalignments in the atoms that form the metal's crystalline structure. Dislocations make metal more vulnerable to being irreversibly bent by outside forces. Their resistance to dislocation gives age-hardened alloys high yield strength and the ability to resist permanent deformation when under heavy strain.

Alloys created by the age hardening process have many uses, especially in applications where high strength and good performance at high temperatures are needed. Maraging steel is used in engine parts and in the construction of missiles and rockets. Age-hardened aluminum alloys made with metals such as nickel, copper, and zinc have frequently been used in the construction of aircraft. The alloy Rene 41, made from nickel alloyed with molybdenum, titanium, chromium, and cobalt, is used in applications involving extreme strain and temperature, such as jet engines.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.

About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.