Disclosed are systems, devices, and methods for additive manufacturing that allow for control of composition and/or porosity of components being manufactured. More particularly, in exemplary embodiments, a secondary material can be used in conjunction with a primary feedstock material in a spatially controlled manner during an additive manufacturing process to control a composition of materials and/or porosity of a manufactured component. Systems, devices, and methods for additive manufacturing are also disclosed that allow for control of a pressure of an atmosphere surrounding a build surface during an additive manufacturing process. More particularly, a pressure of an atmosphere surrounding a build surface can be raised to a pressure greater than standard atmospheric pressure. Various features of the exemplary embodiments of the systems, devices, and methods disclosed can be used together to further control for composition and/or porosity and quality of a manufactured part.