The following steady-state stage II creep rates were recorded for a nickelbase superalloy:
(a) Evaluate all of the terms in the stage II creep-rate equation. Use the strain rate at 811 K and 60 MPa to evaluate the term A.
(b) Determine the stage II creep rate for a stress of 40 MPa and a temperature of 800 K.
(a) There are three unknowns and three conditions so the unknowns can be determined. If the ratio of the strain rates at two different temperatures and the same stress are calculated, then the stress term and the constant A cancel out of the equations. Two of the unknowns are thus eliminated from the equations and the enthalpy of activation is determined. As one point use T1=811 K and a stress of 60 MPa.
Determine the natural log of each side of the equation and insert the value of Boltzmann's constant.
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Fill in the blank(s) with correct word