This paper covers recent work in certain aspects of the design methodology, fabrication, and testing of dual grain structure disks. This type of structure enables the designer to optimize the design for creep resistance and damage tolerance in the rim and high strength in the bore, usually resulting in a lighter weight disk capable of higher temperatures. A trade study was conducted using several advanced, high temperature nickel disk alloys to determine which alloy would be most appropriate for a dual grain structure design. Alloy 10 was selected due to the availability of mechanical properties and favorable balance of properties, which showed a benefit for operating conditions in high temperature regimes. Two dual grain structure Alloy 10 disks were produced using a NASA patented process called Dual Microstructure Heat Treat (DMHT). The transition zone placement was modeled using finite element code and verified in the disks using ultrasonic inspection. A third uniformly fine grain Alloy 10 disk was produced as a baseline for the spin testing. Mechanical properties were measured for fine and coarse grain material, as well as for the transition zone material. Cyclic testing across the transition zone confirmed the metallographic observations of a smooth transition from the fine grain to coarse grain structures and no metallurgical notches. The material data were input into linear and nonlinear finite element models to derive burst speed predictions for both the monolithic and dual structure disks using a conventional disk burst methodology and several advanced burst methodologies. Overspeed testing was conducted at ambient temperature on two fully machined disks: one of dual grain structure material and the other of fine grain material. As expected, the fine grain Alloy 10 disk exhibited higher burst speed due to its higher strength at room temperature. All design models correctly predicted the burst initiation sites and the higher burst speed of the monolithic disk. The advanced methodologies were able to closely match the measured disk yielding behavior and provided more accurate predictions of the actual burst speeds.