THE EFFECT OF NICKEL, CHROMIUM, AND PRIMARY ALPHA-PHASE ON THE CREEP-BEHAVIOR OF TI-6242SI

Elevated temperature creep tests were per-formed on Ti 6242Si deformed to small (<0.002) plastic strains using a highly aligned creep testing apparatus. Specimens were solution annealed at various temperatures below the beta transus (T(beta) - 6-degrees-C to T(beta) - 52-degrees-C) which controlled the volume fraction of primary alpha. Decreases in the amount of primary alpha are associated with decreased primary and steady-state creep rates. The effects of trace levels of the elements Ni and Cr on the creep properties of Ti 6242Si were also studied. Relatively small, additions of Ni (0.075 to 0.093 wt pct), which appeared to segregate to the bcc beta phase, substantially increased the creep rates of this alloy, while additions of Cr up to 0.278 wt pct had little, if any, effect on the creep rates.