Spatial porosity and composition control in additive manufacturing

A method of additive manufacturing, comprising:

• introducing a layer of powdered build material to a build surface in a build chamber of an additive manufacturing device;
• controlling a pressure of a build environment above atmospheric pressure within the build chamber;
• scanning an energy source over at least a portion of the layer of powdered build material such that at least a portion of the powdered build material is fused at least partially to form a build material while controlling a pressure of an environment in the build chamber so as to suppress evaporation of the build material during fusing;
• and
• varying at least one of a relative material composition or the pressure of the environment in the build chamber to change at least a porosity of a manufactured object that includes the layer of powdered build material across one or more of the layer of powdered build material or one or more additional layers of powdered build material of the manufactured object,
• wherein the powdered build material comprises a material that does not have a liquid phase at atmospheric pressure, and wherein scanning the energy source over at least a portion of the layer of powdered build material melts the portion of the powdered build material.