Friction stir processing (FSP) is being developed as a metal working tool to heal casting defects and modify microstructures in a cast NiAl bronze (NAB) alloy for the purpose of substantially increasing mechanical properties. The initial microstructural evolution and resultant mechanical properties for the variety of microstructures created by FSP are reported herein. The dominant microstructural morphologies created by FSP include Widmanstatten, equiaxed fine grain, and a banded or lamellar structure. These microstructures exist concurrently within the FSP zone at different locations and with different volume ratios. The mechanical properties of these different microstructures are established using a micro-tensile test procedure. In addition, bulk mechanical properties are presented to illustrate mechanical properties of the composite microstructure and the Widmanstatten microstructure as a single morphology.