Precipitation hardening, or age hardening, strengthens certain aluminum alloys and precipitation-hardening stainless steels by forming fine dispersed particles during a controlled thermal hold. These precipitates impede dislocation movement and raise strength and hardness.
In many applications, the alloy has first been solution treated and quenched. The aging cycle then determines whether the material reaches under-aged, peak-aged, or over-aged conditions.
Mechanical properties, toughness, stress-corrosion resistance, and dimensional stability all depend on where the cycle ends.
At Braddock, age hardening in hot air would be used when the engineering requirement is a specific precipitation state and corresponding property level rather than a generic bake cycle.
Age hardening is used on alloys whose properties depend on controlled precipitation during thermal aging.
The material is heated to the specified aging temperature and held long enough for the desired precipitate population to form. For aluminum, aging temperatures often fall in the approximate 250°F to 400°F range. For precipitation-hardening stainless steels, aging temperatures vary with the required condition and alloy family.
Because the metallurgical effect is time- and temperature-dependent, over-aging is a real concern.
Excessive aging can coarsen precipitates and reduce peak strength. In some stainless grades, the chosen age also influences toughness and corrosion behavior.
Braddock would control age temperature, time, and furnace uniformity to produce the required condition, such as a specified stainless H-condition or aluminum temper.
