A vacuum chamber is an essential part in which e-beams travel and interact with a powder bed (PB). In the absence of a vacuum, electrons will interact with air molecules and ionize them, thus losing energy, speed, and direction during travel, causing difficulty in processing PB. In some EPBF systems, a vacuum of 10−5 mbar is maintained, which is sufficient to allow unhindered movement of e-beams. Besides, the vacuum enables reactive metals to be processed without getting reacted by oxygen or nitrogen gas. Vacuum has disadvantages: it decreases the melting point of metals and increases their evaporation rate. For an alloy made up of two different metals of different melting points, the evaporation rate of the lower melting point metal will be higher, resulting in its higher loss, causing a change in alloy composition. This is noticed in Ti6Al4V alloy, where the higher loss of Al changes the composition.