Method for making fine-grained Cu-Ni-Sn alloys

Claim 1

Method for producing an article of manufacture comprising a fine-grained body of an alloy comprising the steps, carried out in the order stated, of (1) partially homogenizing a body of the alloy of which an aggregate amount of at least 90 weight percent consists of Cu, Ni, and Sn, said aggregate amount having a Ni content in the range of 5 to 30 weight percent and a Sn content in the range of 4 to 12 weight percent by maintaining said body at a first temperature which is in a first temperature range of 50° C. below to 50° C. above the equilibrium boundary between an alpha phase and an alpha-plus-gamma phase of said alloy for a first time which is in a first time range having a first lower time limit and a first upper time limit, said first lower time limit and said first upper time limit being related to said temperature according to Arrhenius relationships, said first lower time limit being 4 hours and said first upper time limit being 6 hours when said first temperature is 50° C. below said equilibrium boundary, and said first lower time limit being 0.5 hours and said first upper time limit being 1 hour when said first temperature is 50° C. above said equilibrium boundary, (2) cooling said body at a rate sufficiently fast to retain in said alloy a substantial amount of the structure developed by partially homogenizing said body and maintaining said alloy at a second temperature which is in a second temperature range of 75° C. below to 25° C. above the metastable boundary of said alloy, said metastable boundary being CHARACTERIZED IN THAT at temperatures above said metastable boundary but below said equilibrium boundary said alpha-plus-gamma phase is nucleated homogeneously while at temperatures below said metastable boundary said alpha-plus-gamma phase is nucleated discontinuously, aging being carried out for a second time which is equal to or greater than a second lower time limit, said second lower time limit being related to said second temperature according to an Arrhenius relationship, said second lower time limit being 20 hours when said second temperature is 75° C. below said metastable boundary and said second lower time limit being 1 hour when said second temperature is 25° C. above said metastable boundary, (3) completely homogenizing said body by maintaining said alloy at a third temperature which is in a third temperature range of 70° to 25° C. below the solidus of said alloy for a third time which is equal to or greater than 1 hour, and (4) cooling said alloy at a rate sufficiently fast to retain a substantial amount of the structure developed by completely homogenizing said body.