Steady state creep in two Ni-Al alloys

Creep of two Ni-AI alloys containing 4.8 and 7.0 wt pct Al was studied in the temperature range 873 to 1073 K and stress range 30 to 400 MPa. The former alloy represents the solid solution of aluminum in nickel, the latter a solid solution strengthened by NI3AI particles. As to its creep behavior the solid solution alloy belongs to the Class n of solid solu-tions,i.e. the creep controlling mechanism is the same as in pure nickel. From the analy-sis of an effective stress dependence of steady state creep rate it follows that the mo-tion of jogged screw dislocations can be considered as the most probable creep control-ling mechanism. The apparent activation energy of creep in the two phase alloy increases with tempera-ture. This effect is caused by changes in the volume fraction of second phase particles and by the onset of climb around particles at high temperatures. At lower temperatures particles are cut by dislocation pairs.