Process for producing single crystals

A process for producing a single crystal object made of a dispersion strengthened, gamma prime strengthened nickel-base alloy comprising providing a recrystallizable polycrystalline, dispersion strengthened gamma prime strengthened, gamma phase nickel-base alloy mass at least as large as the single crystal object to be produced, providing a single crystal seed object made of a gamma phase nickel-base alloy closely matching in gamma phase lattice parameters the gamma phase lattice parameters of said dispersion strengthened, gamma prime strengthened gamma phase nickel-base alloy in the solution treated condition, fusion welding said seed object to said alloy mass along faying surfaces on said seed object and said alloy mass, zone annealing said welded object to epitaxially grow a single crystal from said welded joint into said alloy mass, said zone annealing being characterized by relative motion between said welded object and a localized steep gradient thermal energy source having an intensity sufficient to raise the local temperature of said welded object above the solvus temperature of the gamma prime phase in said alloy mass to thereby provide a single crystal at the expense of the existing polycrystalline structure and thereafter, if necessary, discarding the seed single crystal and excess metal of said mass to provide a single crystal dispersion strengthened, gamma prime-containing, gamma phase nickel-base alloy object.