Effect of initial temper on the creep behavior of precipitation-hardened WE43 alloy

The effect of initial tempers with different characteristics of precipitates and contents of supersaturated solute atoms, including the homogenized, peak-aged and over-aged conditions, on the tensile creep behavior of WE43 alloy has been investigated at 523 K. Results show that the peak-aged alloy at 523 K obtained superior creep resistance than the homogenized, peak-aged at 498 K and over-aged at 523 K alloy. A uniform dispersion of β precipitates was dynamically formed within steady-stage creep microstructure of the homogenized WE43 alloy after creep deformation of 200 h. It is found that the precipitate size and distribution is similar with the alloy aged equal time without the applied stress. In addition, the WE43 alloy in all tempers obtains similar precipitate size and distribution in their steady-stage creep microstructures. Therefore, it is inferred that the various initial tempers mainly affect the primary creep stage. Furthermore, numerous dislocations were detected between precipitates and the stress exponent n is 4.5, which is close to 5. Thereby, dislocation climb is suggested to be the creep mechanism. The reason for the peak-aged alloy at 523 K obtained superior creep resistance is that the initial uniform dispersion of β″ and β′ precipitates have smaller precipitate size and higher precipitate density than that of the homogenized and over-aged alloy, which are more effectively to hider dislocation climb. However, a deterioration of creep resistance was occurred in the peak−aged alloy at 498 K due to precipitate recovery when crept at 523 K. As a consequence, WE43 alloy in peak-aged temper at 523 K achieves the highest creep resistance.