Materials, Properties and Design

· The diagram shows how the alloy's yield stress depends upon composition and the temperature at which the yield stress (proof stress) is measured. Good high temperature performance requires a high yield stress at temperature.
· As the Aluminum content increases to 21 atomic %, the volume fraction of γ'-phase increases and the temperature to which it is stable increases.
· The γ'-phase dissolves in the γ phase as the temperature is increased for lower aluminum concentrations and the material's yield stress is reduced because of the absence of the second phase.

From: Weidman, Lewis, & Reid, "Structural Materials," Butterworths (1990)