Theory:

Heat treatment is the process of heating and cooling metals in order to achieve desired material properties. Heat treatment is very important in strengthening of Aluminum 6013, to make it suitable for high strength aerospace applications. Aluminum alloys are not as corrosion resistant as pure aluminum, so heat treatment is also used to improve its corrosion resistance. Heat treatments cause precipitation hardening which promotes the formation of small, hard precipitates that interfere with the motion of dislocations. In order for precipitation hardening to occur, the temperature of the alloy must be raised into the single phase region so that all of the precipitates dissolve. During solution heat treatment, the alloy is heated to a suitable temperature and held at this temperature for a sufficient length of time to allow a desired constituent to enter into solid solution. This is followed by rapid cooling to hold the constituent in the solution. The material is then in a supersaturated, unstable state, and may subsequently exhibit Age Hardening. Precipitates may also form slowly at room temperature, which is referred to as natural aging. In the aluminum 6013 alloy, the precipitation process occurs during aging heat treatment. Artificial aging, usually after welding, generates precipitates that cause considerable hardening in aluminum alloys.


Method:

We decided to heat treat to the T4 temper because it has better stretch forming characteristics than other aerospace aluminum alloys. Parts can be formed in the T4 condition and then aged to the T6 temper. We heat treated two samples: a sample that had been cast and then welded, and a sample that had only been cast. We solution heat treated the samples at 1060°F for 30 minutes. We allowed the furnace to heat up for 30 minutes to ensure that it reached the uniform desired temperature when we put the samples in. The heating was followed by a cold water quench to result in W temper. Aging then occurred naturally at room temperature for T4 temper. After this, we formed the T6 temper by solution heat treating our samples at 375°F for 4 hours, followed by air cooling.


Application to Fuselage:

Heat treating aluminum 6013 is necessary to increases strength and hardness. High strength is required for aerospace applications, and the fuselage needs to be able to withstand high tensile and compressive stresses. The T4 temper is good for forming, which can be used for making the fuselage panels. The T6 temper is better to use for the final product because it has a higher strength.