Three-dimensional printing of three-dimensional objects

A three-dimensional object, comprising:

• a plurality of layers of hardened material, wherein a single layer of the plurality of layers of hardened material includes (1) a core portion, (2) a skin portion, and (3) a plurality of melt pools;
• wherein the core portion is characterized as having a first microstructure;
• and
• wherein an exterior surface of the skin portion (i) corresponds to at least a fraction of an exterior surface of the three-dimensional object, and (ii) is characterized as having a second microstructure that is different than the first microstructure, and
• (a) wherein the three-dimensional object comprises at most about 15% porosity and/or (b) wherein the exterior surface of the skin portion is a bottom skin portion of a structure that extends from the core portion of the three-dimensional object, wherein the structure is such that a vector (I) is normal to the exterior surface at a point on the exterior surface, (II) is directed into the structure, and (III) forms an angle by intersecting with (A) a layering plane of the plurality of layers of hardened material and/or (B) a plane parallel to the layering plane, and wherein the angle has a value of at least sixty degrees and at most ninety degrees.