In situ processing consists of heavily deforming a two-phase alloy of mutually immiscible elements to produce composite sheet or wire. In the well-studied Cu(fcc)-Nb(bcc) system, severe deformation by swaging and drawing reduces niobium filament phase thicknesses from 1–5 μm (as-cast) to 0.007–0.030 μm (after deformation). Cu-20% (vol.) Nb ultimate tensile strengths exceed 2000 MPa for material deformed to a true strain of η=12, where η=In (areaoriginal/areafinal). In a study on in situ strengthening in immiscible hexagonal close-packed metals, Ti-50 wt % Y and Ti-20 wt % Y alloys were deformed by hot extrusion, hot swaging, and cold swaging. As deformation progressed, samples were taken for tensile testing and examination by SEM and TEM. Ti-Y alloys deformed to final true strains of 6.6 (Ti-50Y) and 7.6 (Ti-20Y) contain nanofilaments (100 nm phase spacing) similar to those of deformation-processed Cu-20Nb at comparable strains. The ultimate tensile strengths of the alloys approximately tripled as deformation progressed from the as-cast condition to these final true strains, although the exponential strength increase seen in Cu-Nb alloys was not observed.