Why Is Aging Important for Heat Treating?

Construction materials will tend to transform over time when they are exposed to natural environmental conditions. For example, you’re likely to see changes in the color and texture of metal surfaces as an oxide layer forms on them. This process of aging shows up frequently in copper, aluminum, lead, zinc and steel.

The aging process can be taken advantage of and used as a sort of natural heat treating process. Companies have developed a variety of aging techniques to achieve different results. Here is a quick overview of some of those techniques used by metallurgical services in Gastonia, NC.

Artificial or natural aging

Natural aging refers to aging that occurs naturally at room temperature. Artificial aging, then, occurs when the metal alloy is treated at elevated temperatures to accelerate the changes in properties you’d find in the natural aging process and as a result of casting and forging. The chemical properties in the cast and forged materials will change quite slowly at room temperature, so this process speeds it up and also allows for more control and higher quality in those property changes. Manufacturers are also able to use artificial aging to make parts ready for machines much faster.


This technique is a type of aging process that involves freezing or stopping any internal changes that might typically take place in an alloy at room temperature.

Strain hardening

This process involves changes that occur through aging or hardening due to cold-working the alloy.

Precipitation hardening

The aging process is just one of several steps featured in the process of precipitation hardening, with the others being solution treatment and quenching. In precipitation heat treatment, the solution gets heated up to a moderate temperature to induce precipitation. The material then gets held at that temperature for a specific period of time.

For precipitation hardening to occur, there must be an appreciable maximum solubility, a solubility curve that demonstrably reduces with the temperature and an alloy composition that is below the maximum solubility figure. It is important to make sure the aging occurs below the equilibrium solvus temperature and below the metastable miscibility gap known as the Guinier-Preston (GP) solvus line.

Why go through all the trouble of aging alloys before working them? Because this helps to increase the strength of the alloys, and allows them to acquire various other beneficial characteristics, including high coercivity. Aging also helps create equilibrium in the metal and to cut out any potentially unstable conditions that may have been a result of previous operations. While the aging process can have some damaging effects, such as reduced ductility and resilience of the alloy, those effects can be largely mitigated by using heat treatment or special alloying processes.

For more information about the benefits of aging in heat treating and the types of metallurgical services in Gastonia, NC that can be used to accomplish this, we encourage you to contact the team at J. F. Heat Treating Inc. We’d be happy to answer any questions you have, and look forward to working with you soon.

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