A buckling restrained brace includes a deformable core contained within an outer casing. Ends of the core protrude from the casing for connection to a frame or other structure. A length of the deformable core between its ends, referred to as the gauge or yielding section, is capable of deforming during an earthquake or blast loading. The gauge section is differentially heat treated from the ends so that the gauge section has a lower yield strength than the ends. The casing provides containment of the core to prevent buckling of the core. A metal foil interface or unbonding layer is provided between the deformable core and the casing so that the deformable core does not bind to the casing. The buckling restrained brace provides significant performance improvements over prior art BRBs coupled with simplified assembly.