The are 3 must use alloys for handlebars: the 6000, the 2014 and the 7000. Normally for the 6000 we use the 6061 and the for the 7000 type we use the 7050/7075. The 6000 alloy is the most used type, while the 7000 alloy is lighter but more costly (almost the double cost of the 6000). As the aluminum is quite difficult to be manufactured, all these alloys need to be treated. Starting from the bar, the tube is cut at the length (for alloy we start from a diameter of 31.8) which is a good fit for the clamping of the stem. After the cutting, as the aluminum has a thickness in between 2.4 and 3.2, in order to make the aluminum handlebar lighter, there are machines at disposable for “drawing” and for performing “double butting”: the tube is extended in all its length: in the center the original wall thickness is kept (as for ensuring safety) and on the extremity the tube is extended and the original wall thickness become smaller and thinner as for gaining weight
After this double butting process, the aluminum tube is under big stress. When dealing with the 7000 type of alloy, a further operation is needed: the annealing process.
The 7000 alloy needs 3 steps in order to be reduced from 31.8 (being the center diameter) to 22.2. During these steps, as for the stress, handlebars risk to result in being excessively hard: further operations such as bending (for road bikes) are needed. Part of these operations includes entering an oven in order to receive a treatment called T4. The purpose is to restore the aluminum properties so that the material, if bended, can resist instead of breaking.
After the T4 process, the bar is ready to be treated and machined. This machining is usually a bending operation. After the bar has been stretched and properly machined, the bar is put a second time in an oven. This time, another process called T6 is implemented. The T6 process grants a high level of hardness from which is it almost impossible to be moved.
Once the T6 process is finished, the handlebar is finally ready.